Datasets:

marianna13
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litarch

+{"file": "ukhsdr0429_NBK390252/abs3.nxml", "text": "Background\nThis study began as a result of questions posed by pregnant women who were scheduled to have cancer surgery during their pregnancy. Women wanted to know the risks of surgery to pregnancy, including the risks of a spontaneous abortion, stillbirth and premature delivery. However, there is limited available evidence quantifying these risks. Furthermore, of the evidence that is available, none relates directly to NHS outcomes and there are no current NHS guidelines regarding non-obstetric surgery in pregnant women.\nObjectives\nOur main objectives were to:\ncarry out a descriptive analysis of the data, describing counts of each adverse outcome by year, maternal age, procedure type, socioeconomic status and trimester of pregnancy\nestimate the risk of each adverse outcome in women who have had surgery and compare this with the risks in those women who have not had surgery\nestimate the risk associated with common procedure groups.\nMethods\nHospital Episode Statistics (HES) is an administrative database that includes records of all patient admissions and day cases in all English NHS hospital trusts. We analysed HES maternity data collected between 2002\u20133 and 2011\u201312, and identified women who underwent non-obstetric surgery while pregnant.\nThe study outcomes were based on mothers\u2019 records (spontaneous abortion, preterm delivery, caesarean delivery, maternal death and long inpatient stays) and infants\u2019 records (stillbirth and low birthweight).\nWe used the adjusted odds ratio obtained directly from the logistic regression model to estimate the relative risk (RR) of each adverse birth outcome in pregnancies in which non-obstetric surgery was carried out compared with pregnancies with no record of surgery.\nWe used the logistic regression model to estimate marginal probabilities of each outcome of interest. This allowed us to compare outcomes between two populations whose only difference was in the exposure, permitting us to estimate adjusted RR, attributable risk and the number of operations associated with one additional adverse birth outcome [number needed to harm (NNH)]. Confidence intervals (CIs) for each measure of effect were estimated using the non-parametric bootstrap method. The end points of 95% CIs were defined as the 2.5th and 97.5th percentiles measured across the bootstrap samples.\nResults\nA total of 6,486,280 pregnancies were identified in the period April 2002 to March 2012. Spontaneous abortions accounted for 5.8% of all pregnancies. The number of maternal deaths following spontaneous abortion or delivery was very small and corresponded to a rate of 4 per 100,000 pregnancies. Among our cohort, 7.5% of deliveries ended in preterm birth and 23.9% ended in elective or emergency caesarean section. We identified 47,628 (0.7%) women who had non-obstetric surgery during their pregnancy. The most common surgical group was abdominal (26.2%), followed by dental (11.3%), nail and skin (10.0%), musculoskeletal (9.6%), and ear, nose and throat (ENT) (6.4%). There were 3062 cases of appendectomy and 1306 cases of cholecystectomy.\nAfter adjusting for potential confounders, we found that pregnant women who underwent non-obstetric surgery had a higher risk of adverse birth outcomes than those women who did not have surgery. The RR for spontaneous abortion was 1.13 (95% CI 1.09 to 1.17); for preterm delivery was 1.43 (95% CI 1.39 to 1.47); for maternal death was 4.72 (95% CI 2.61 to 8.52); for caesarean section was 1.21 (95% CI 1.19 to 1.23); for long inpatient stay was 1.22 (95% CI 1.19 to 1.25); for stillbirth was 1.64 (95% CI 1.50 to 1.81); and for low birthweight was 1.49 (95% CI 1.44 to 1.54). For NNHs, we estimated that, for every 143 pregnancies in which a surgical procedure was carried out, there was one associated additional spontaneous abortion; for every 287 procedures there was one associated additional stillbirth; for every 31 procedures there was one associated additional preterm delivery; for every 25 procedures there was one associated additional caesarean section; for every 50 procedures there was one associated additional long inpatient stay; for every 39 procedures there was one associated additional low-birthweight baby; and for every 7692 procedures there was one associated additional maternal death.\nThe additional risk of having an adverse birth outcome associated with abdominal surgery was higher than for women who did not have surgery during their pregnancy. Abdominal surgery during pregnancy was associated with an increase in the risk of spontaneous abortion and caesarean delivery of 5.0 percentage points.\nWe found that musculoskeletal, ENT, breast or dental procedures during pregnancy were associated with higher risks of some adverse birth outcomes.\nLimitations\nWe have no means of disentangling the effect of the surgery from the effect of the underlying condition itself. Many spontaneous abortions will not be associated with a hospital admission and, therefore, will not be included in our analysis. A spontaneous abortion may be more likely to be reported if it occurs during the same hospital admission as the procedure, and this could account for the increased risk associated with surgery during pregnancy. Key data items that are necessary to determine parity, gestational age, birthweight and stillbirth are missing.\nConclusions\nThis is the first study to report the risk of adverse birth outcomes following non-obstetric surgery during pregnancy across NHS hospitals in England. We have no means of disentangling the effect of the surgery from the effect of the underlying condition itself. We found that non-obstetric surgery during pregnancy was associated with a significantly higher risk of all the outcomes we looked at, although, because of data completeness issues and the potential for ascertainment bias, we have some reservations over the findings associated with spontaneous abortion. The overall attributable risk of an adverse birth outcome in women who underwent surgery during pregnancy compared with women who did not was generally low.\nOur observational study can never attribute a causal relationship between surgery and adverse birth outcomes. However, we believe that our findings and, in particular, the NNHs improve on previous research, utilise a more recent and larger data set based on UK practice and are useful reference points for any discussion of risk with prospective patients.\nFuture work\nFurther research is needed to evaluate the impact of non-obstetric surgery on the baby (e.g. neonatal intensive care unit admission, prolonged length of neonatal stay, neonatal death) and could be assessed by linking the maternal and baby records within the HES database. The use of large clinical databases, such as EuroKing Maternity systems (www.euroking.com/), linked to the HES database could be usefully exploited for this purpose.\nFunding\nFunding for this study was provided by the Health Services and Delivery Research programme of the National Institute for Health Research.", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/g2.nxml", "text": "American College of Obstetricians and Gynecologists\nconfidence interval\near, nose and throat\nHospital Episode Statistics\nInternational Classification of Diseases, Tenth Edition\nNational Institute for Health Research\nnumber needed to harm\nOffice of Population, Censuses and Surveys\u2019s Classification of Surgical Operations and Procedures\nOffice of Population, Censuses and Surveys\u2019s Classification of Surgical Operations and Procedures, version 4\nodds ratio\nRoyal College of Midwives\nRoyal College of Obstetricians and Gynaecologists\nrelative risk", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/s4.nxml", "text": "We aimed to estimate the risk of adverse birth outcomes in pregnancies in which surgery was carried out and to compare this with the risk in pregnancies in which no surgery was recorded, and, also, to estimate the risk associated with common procedure groups.\nIn this chapter we summarise the main results and their relation to previous studies. We then note the strengths and limitations of our analysis and suggest future work.\nKey findings\nWe identified 6,486,280 pregnancies, among which non-obstetric surgery was carried out in 47,628 (0.7%), in the period April 2002 to March 2012.\nThe most common surgical procedure group was abdominal (26.2%), followed by dental (11.3%), nail and skin (10.0%), musculoskeletal (9.6%), ENT (6.4%) and perianal (6.2%). There were 3062 cases of appendectomy and 1306 cases of cholecystectomy.\nNon-obstetric surgery during pregnancy was associated with a higher risk of adverse birth outcomes than if no surgery was carried out. We estimated that for every 143 pregnancies in which a surgical procedure was performed, there was one additional spontaneous abortion (with a hospital admission); for every 31 procedures there was one additional preterm delivery; for every 7692 procedures there was one additional maternal death in hospital; for every 25 procedures there was one additional caesarean section; for every 50 procedures there was one additional long inpatient stay; for every 287 procedures there was one additional stillbirth; and for every 39 procedures there was one additional low-birthweight baby.\nDental, perianal, breast, cancer, abdominal, ENT and musculoskeletal procedures were associated with a higher risk of adverse birth outcomes than no surgery.\nFor almost half of operations (42.0%), no information about when in pregnancy the procedure was carried out was recorded.\nFor pregnancies in which gestational age was recorded, the RR for preterm delivery, caesarean section, stillbirth and low birthweight was between 20% and 30% higher for those operations carried out in the third trimester than for those performed in the first trimester. There was little difference by trimester of operation in the risk of a long inpatient stay.\nFindings in relation to other studies\nSpontaneous abortion associated with hospitalisation and preterm delivery\nWe found a high RR (1.13) for spontaneous abortion associated with hospitalisation for surgery during pregnancy. Duncan et al.2 found an even higher RR (1.58) of abortion associated with a general anaesthetic in their 1986 Canadian study of 2565 pregnant women. Our study is much larger and more recent, perhaps reflecting improvements in surgery, but (like Duncan et al.\u2019s2 study) is unable to dissociate the risk of surgery from the risk of anaesthesia or the underlying condition for which the procedure was carried out. Other studies have focused on abdominal surgery. We found that, compared with no surgery, abdominal surgery was associated with an even higher risk of spontaneous abortion (associated with a hospital admission) (RR 1.90, 95% CI 1.81 to 1.99) and of preterm delivery (RR 1.62, 95% CI 1.54 to 1.70). Our study\u2019s definition of spontaneous abortion is limited by the information that is held in administrative databases which includes spontaneous abortion only if this is recorded during a hospital admission. A large number of women whose pregnancies end in spontaneous abortions are never hospitalised. Gerstenfeld et al.35 performed a retrospective review of all non-obstetric abdominal procedures in a women\u2019s hospital at the University of Southern California School of Medicine during a 7-year period from 1991 to 1998. They found no significant difference in preterm delivery rates between women who underwent abdominal surgery and those who did not (OR 1.13, 95% CI 0.56 to 2.25; p\u2009=\u20090.84), and only two cases of spontaneous abortion following surgery. The post-surgical follow-up period in this study was short (a maximum of 4 weeks) and only 67% of subjects were followed up. The study was small and included only 106 women who underwent surgery. We found a significant difference between laparoscopic and open abdominal surgery for risk of spontaneous abortion (RR 3.82, 95% CI 3.29 to 4.41). Gerstenfeld et al.35 found no significant difference, but, again, their study was limited by small numbers. There may be reluctance by surgeons to perform laparoscopic surgery beyond 26\u201328 weeks\u2019 gestation because of previous evidence which suggests that \u2018A gestational age of 26 to 28 weeks seems to be the limit for successful completion of laparoscopic surgery\u201936 and, although this evidence has since been refuted,37 the perception and practice may persist. Our analysis of open versus laparoscopic abdominal procedures by trimester (where gestational age at delivery was recorded) confirms that this remains the case, as the number of laparoscopic operations performed during the first trimester was nearly five times the number of open operations, whereas, in the third trimester, the number of open operations was 2.5 times the number of laparoscopic procedures. Unfortunately, in the case of spontaneous abortion, gestational age was frequently not recorded, so we were unable to examine the relationship between timing of procedures and outcome. However, there is no reason to doubt that the pattern would be similar. Within our definition of spontaneous abortion (associated with hospitalisation), we look only for operations 3 months prior to the event (which, by definition, occurs before week 24 of pregnancy) and women are likely to be admitted to hospital only during the second trimester. We are, therefore, picking up selected cases that are more likely to have a higher proportion of laparoscopies. We are unable to identify women who suffer spontaneous abortions who are not admitted. In addition, as is true for other studies and all our outcomes, we have no means of disentangling the effect of the surgery from the effect of the underlying condition itself.\nFor abdominal surgery, we found a reduced risk of preterm delivery (RR 0.85, 95% CI 0.77 to 0.94); Gerstenfeld et al.35 found no significant difference in preterm delivery rate, but we suspect that, again, the small sample size and period from which their cohort was drawn may explain this difference. Two other studies compared pregnancy outcomes following laparoscopic and open appendicectomy38,39 and found no difference in the rates of preterm delivery. Sadot et al.38 performed a hospital-based retrospective review of 65 pregnant women who underwent appendectomy for presumed appendicitis from 1999 to 2008. They calculated the overall preterm delivery rate and the rate of preterm delivery within 1 month of operation. In neither case was there any statistically significant difference between the laparoscopic and open groups. The authors did not analyse rates of spontaneous abortion.\nMaternal death in hospital\nIn our study we identified 235 maternal deaths, which corresponds to a maternal death rate of 4 per 100,000 pregnancies. Our estimate is much lower than national estimates (10 per 100,000 according to the report Saving Lives, Improving Mothers\u2019 Care40) because we identified only maternal deaths occurring in the same admission as the delivery or spontaneous abortion. We were not able to capture maternal deaths of women who did not deliver or deaths occurring following discharge. We estimated the RR of non-obstetric surgery during pregnancy to be 4.72 (95% CI 2.61 to 8.52). The baseline risk of maternal death is fortunately very low and translates into a NNH of 7692, which is the number of procedures associated with one additional maternal death. This number was based on only 12 deaths among pregnant women undergoing surgery in our cohort, and so the CIs are wide. Again, we have no means of disentangling the effect of the surgery from the effect of the underlying condition itself. Only one previous study has reported the maternal death of a woman undergoing non-obstetric surgery during pregnancy.41 This study compared laparoscopic cholecystectomy with open cholecystectomy in pregnant women during the period 1992\u20136. During the 5-year period of the study, 46 pregnant women who underwent cholecystectomy were identified. The maternal death occurred in a 27-year-old woman who underwent elective laparoscopic cholecystectomy at 20 weeks\u2019 gestation. On postoperative day 15, she presented to the emergency department and died following a laparotomy.\nStillbirth and low birthweight\nOur study revealed that non-obstetric surgery during pregnancy is associated with an increased risk of stillbirth and low birthweight. We found that pregnant women who underwent non-obstetric surgery had an attributable risk of 0.4% for stillbirth and 2.6% for low birthweight compared with women who did not have surgery. However, there were no significant differences in the risk of low birthweight and stillbirth between those women undergoing laparoscopic and those undergoing open abdominal surgery. A Swedish study3 analysed outcomes of 5405 patients who had had an operation during pregnancy, out of a total of 720,000 Swedish births between 1973 and 1981, and concluded that the incidence of stillbirth was not increased in women having an operation. However, the incidence of very low birthweight and low-birthweight infants was increased. Mazze and K\u00e4ll\u00e9n4 investigated appendectomy and laparoscopic surgery, and did not observe a statistically significant increase in stillbirth. However, the authors concluded that the mean birthweight in the operated group was, on average, 78\u2009g less than the expected birthweight. Furthermore, compared with the general population, women undergoing operations during 3\u201323 weeks\u2019 gestation demonstrated a shift in distribution towards an excess of infants with a birthweight <\u20093000\u2009g. Another Swedish study5 found no difference in the birthweight of singleton infants born to women who underwent laparoscopy between 4 and 20 weeks of gestation. More recent studies on appendicectomy39,42 compared the effects of laparoscopic appendectomy with those of open appendectomy during pregnancy. There were no significant differences in the birthweight between the two groups. Moreover, Jenkins et al.43 reported that general anaesthesia, longer surgery duration and intra-abdominal procedures are associated with lower birthweight.\nCaesarean section and long inpatient stays\nWe found a significant effect in the adjusted RR for caesarean section of 1.21 (95% CI 1.19 to 1.23); however, this reduced to 1.17 (1.15 to 1.19) when the more appropriate Austin method30 was used for common outcomes. We also found a higher risk of long inpatient stays (RR 1.22, 95% CI 1.19 to 1.25). We could not find any previous studies reporting caesarean delivery and long inpatient stays in women who had surgery during their pregnancy.\nStudy strengths and limitations\nThis is the first study to report the risk of adverse birth outcomes following non-obstetric surgery during pregnancy across NHS hospitals in England. One important strength of this research is the use of the large and rich administrative data set. We extracted data for nearly 6.5 million pregnancies between 2002\u20133 and 2011\u201312, 10 times the total in the published literature to date. Furthermore, our data are much more recent and better represent current outcomes.\nAnother strength is that we estimated adjusted attributable risk and the NNH. The use of Austin\u2019s analytical method30 was a particular strength here, as this allowed us to compare outcomes between two populations whose only difference was the exposure (non-obstetric surgery during pregnancy). These measures are more useful than an OR to women who want to be informed of the risk associated with a non-obstetric procedure, above and beyond the background risk.\nAppropriateness of controls\nThe absolute key limitation of our study is that we have no means of disentangling the effect of the surgery from the effect of the underlying condition itself. Thus, we are able to compare only women who have surgery during pregnancy with women who do not. The ideal study population would be all women who require surgery during pregnancy to enable us to compare outcomes in women who actually had surgery with those who did not. Ideally, participants would be randomised into each group. However, withholding surgery in pregnant women who require treatment would be ethically challenging. From our study we have no way of determining the risk that the underlying condition would result in an adverse birth outcome. However, we still believe that the NNH, in particular, is a useful reference point for any discussion of risk with prospective patients. A further limitation, although certainly not unique to our study, is that we treat surgery during pregnancy as a homogeneous intervention and are unable to disentangle the independent effects of anaesthesia, pre-/peri- and post-operative care, as well as the surgery itself, all of which may influence the outcome of pregnancy. Therefore, we are not able to estimate the independent contribution to the risks of an adverse outcome during pregnancy of each component of this complex intervention.\nOur study arose as a direct result of questions posed in the high-risk obstetric anaesthetic clinic by patients who wanted to know the statistical risks of an adverse outcome to their pregnancy. For some combinations of procedures and outcomes we have found no excess risk, and that may help to reassure mothers and remove barriers to potentially unnecessary delays to treatment.\nData quality\nThe second limitation relates to data quality and completeness. Submission of HES records is mandatory and, in general, coverage is very high. Most debates around HES data quality concern the primary and secondary diagnostic and procedure field.9,44\u201346 Nonetheless, a recent systematic review of discharge coding accuracy in routine UK data found that primary diagnosis accuracy has improved from 73.8% to 96.0% in the 10 years since the introduction of Payment by Results.47 Not all delivery records contain supplementary information, although the percentage of records with a complete maternity tail has improved over time.48 We found that the proportion of missing values for the key data items of parity, gestational age, birthweight and stillbirth decreased from 24%, 48%, 26% and 2.8%, respectively, in 2002\u20133 to 16%, 12%, 10% and 0.15%, respectively, in 2011\u201312. We also carried out sensitivity analyses, comparing analyses based on assumptions about missing variables with analyses in which we excluded records with missing variables and found no major differences in RR and its 95% CIs. Administrative data have more general limitations in the recording of other potential confounders. It is well known that body mass index, smoking status and environmental factors, such as air pollution, are important risk factors for adverse outcomes in pregnancy.49\u201352 However, these variables are not recorded in the HES data set.\nThere are previously documented missing or invalid values in the HES database for patient identifiers, dates of admission, discharge or procedure, method of admission or other key fields.24,53 Improvements in the quality of the HES data are visible but, importantly, there are unlikely to be biases in recording for women undergoing non-obstetric surgery during their pregnancy, which means that data incompleteness and inaccuracy are unlikely to wholly account for findings.\nSpontaneous abortion\nA specific limitation around spontaneous abortion is that many spontaneous abortions will not be associated with a hospital admission and these will not be included in our analysis. It is certain, therefore, that our category of spontaneous abortion associated with hospitalisation is only a small proportion of all spontaneous abortions. A spontaneous abortion may be more likely to be reported if it occurs during the same hospital admission as a procedure, and this could account for the increased risk associated with surgery during pregnancy. However, only 1.8% (56/3176) of spontaneous abortions associated with hospitalisation actually occurred in the same admission as the procedure. Gestational age at delivery was essential to determine the trimester in which the procedure was carried out, but was not present on our records for spontaneous abortions associated with hospitalisation. We have already discussed the probable explanation for the increased risk for laparoscopic versus open abdominal surgery for spontaneous abortion. In addition, some of the risk factors that appear to be protective for this outcome, such as gestational diabetes and obstetric surgery, may simply reflect the fact that most spontaneous abortions occur before there is an opportunity for these potential risk factors to occur or be recorded. We carried out a sensitivity analysis in our logistic regression to exclude gestational diabetes, obstetric surgery and operations on the amniotic cavity from the model for spontaneous abortion associated with hospitalisation and found that the adjusted ORs did not change.\nBecause of the serious potential for ascertainment bias, temporal issues around the recording of risk factors and other unaccounted for confounding related to gestational age, we urge caution when interpreting the risk of spontaneous abortion associated with non-obstetric surgery during pregnancy.\nStatistical analyses\nDespite the evident advantage of the method introduced by Austin,30 particularly for common outcomes (e.g. caesarean section), the size of the database meant that the calculation of the CIs for one outcome took several days of computing time to run. We therefore had to be selective and were forced to make a priori judgements about which statistical analysis to present. Consequently, not all CIs were estimated. However, the RRs estimated using adjusted ORs obtained directly from the logistic regression, in most cases, were the same as or only slightly different from the RRs obtained using the Austin method.30\nWe carried out two-level logistic regression to investigate the effects of hospitals on the adverse birth outcomes. The interclass correlation coefficients were close to 0, meaning that adjusting for the clustering of pregnancies within each trust would be unlikely to affect our results.\nRecommendations for further research\nOur study has demonstrated that there is a statistically significant increase in the risk of adverse birth outcomes following non-obstetric surgery during pregnancy in England. However, we have identified a number of limitations that would benefit from further research to usefully inform a variety of medical practitioners and the general public. We offer a small set of recommendations for further research:\nFurther research is required to evaluate the association of non-obstetric surgery and spontaneous abortion.\nFurther research is needed to evaluate the impact of non-obstetric surgery on the baby (e.g. neonatal intensive care unit admission, prolonged length of neonatal stay, neonatal death) and could be assessed by linking the maternal and baby records within the HES database. Use of large clinical databases, such as EuroKing Maternity systems (www.euroking.com/), linked to the HES database could be usefully exploited for this purpose.\nDissemination activity\nTo date, we have disseminated findings from this project as an oral presentation at the Applied Epidemiology Scientific Meeting in Warwick University, March 2015.\nWe presented some results to an international science competition FameLab (Lithuania) in April 2015 (www.famelab.lt/apie/).\nWe shall give an oral presentation at the Dame Hilda Lloyd Congress Medal plenary session at the Royal College of Obstetricians and Gynaecologists (RCOG) World Congress in June 2016.\nWe have written up our findings in an academic peer-reviewed journal.54\nWe have already engaged with the British Society of Endocrine and Thyroid Surgeons and the Association of Breast Surgery, both of which have guidelines. Both organisations have agreed to consider hosting guidance that we produce on their websites.\nThe data will also be used by institutions such as RCOG and the American College of Obstetricians and Gynecologists (ACOG). We are in contact with the RCOG, and it is supportive of our study and would assist in the dissemination of findings to both health-care professionals and the public.\nWe shall contact the ACOG directly following publication to ensure that they are aware of our study. We shall also discuss the possibility of publishing a British guideline taking into account all available evidence, with the RCOG, the Anaesthetists Association of Great Britain and Northern Ireland and the Royal College of Midwives (RCM).\nWe shall contact the RCM directly to ensure that it is aware of our study, and to make sure that it is included in any joint guidelines produced.\nWe shall ensure that a lay summary of our peer-reviewed findings is available online, initially on the Imperial College London website.", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/ack1.nxml", "text": "This report represents independent research supported by the National Institute for Health Research (NIHR). The views expressed are those of the authors and not necessarily those of the NHS, NIHR or the Department of Health. The Dr Foster Unit at Imperial is partly funded by a research grant from Dr Foster (an independent health-service research organisation). We are also grateful for support from the NIHR Biomedical Research Centre funding scheme.\nWe would also like to thank Emma Cooper for her input into the original proposal and her assistance in overseeing the study as a patient representative.\nContributions of authors\nPaul Aylin was instrumental in securing the data.\nPaul Aylin, Alex Bottle and Violeta Balinskaite carried out the analysis and wrote the first draft.\nAll authors contributed to the original research proposal, helped to refine the classification of outcomes used and the procedure groups for further analysis, and commented on subsequent drafts of the report.\nEthics\nWe have permission from the Confidentiality Advisory Group under Section 251 of the NHS Act 2006 (formerly Section 60 approval from the Patient Information Advisory Group) to hold confidential data and analyse them for research purposes [PIAG 2\u201305(d)/2007]. We have approval to use them for research and measuring quality of delivery of health care from the South East Ethics Research Committee (10/H1102/25).\nPublications\nBalinskaite V, Bottle A, Sodhi V, Rivers A, Bennett PR, Brett SJ, et al. The risk of adverse pregnancy outcomes following nonobstetric surgery during pregnancy: estimates from a retrospective cohort study of 6.5 million pregnancies [published online ahead of print September 14 2016]. Ann Surg 2016.\nData sharing statement\nUnder the terms of our contract with the Health and Social Care Information Centre, we are allowed to hold our data only for as long as is specified in our data release agreement (usually 3 years unless renewed) and we are unable to share these data with other organisations. At the end of our contract we are obliged to delete the data. All source data, however, are available on application to the Health and Social Care Information Centre.\nDisclaimers\nThis report presents independent research funded by the National Institute for Health Research (NIHR). The views and opinions expressed by authors in this publication are those of the authors and do not necessarily reflect those of the NHS, the NIHR, NETSCC, the HS&DR programme or the Department of Health. If there are verbatim quotations included in this publication the views and opinions expressed by the interviewees are those of the interviewees and do not necessarily reflect those of the authors, those of the NHS, the NIHR, NETSCC, the HS&DR programme or the Department of Health.", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/s1.nxml", "text": "Patient concerns\nOur study arose as a direct result of questions posed in the high-risk obstetric anaesthetic clinic by patients who were scheduled to undergo cancer surgery while pregnant. Patients wanted to know the statistical risks of an adverse outcome to the pregnancy, including miscarriage, stillbirth, premature delivery or problems following birth such as admission to neonatal intensive care. Unfortunately, the current evidence base is not sufficient to answer these questions and, therefore, this constitutes a \u2018knowledge gap\u2019.\nA postal survey of women who had undergone non-obstetric surgery during pregnancy in our maternity unit over a 5-year period was then conducted. All respondents (75% response rate) expressed concern regarding the lack of availability of statistical data that could guide their decision. Although they felt that they were adequately counselled, they all agreed that, if there had been more information available, they would have been more confident in their decision-making and less anxious regarding the pregnancy outcome.\nPrevious literature\nPrevious literature suggested that non-obstetric surgery is carried out in approximately 1\u20132% of pregnancies,1 with common operations being appendectomy, cancer surgery and orthopaedic procedures. In this situation, women and their doctors are understandably anxious about the risk of harm to the fetus. However, there is limited available evidence quantifying the risks of miscarriage (fetal loss before 24 weeks\u2019 gestation), stillbirth (fetal loss after 24 weeks\u2019 gestation), premature labour or infant death post delivery.\nA Canadian study investigated data from 2656 women between 1971 and 1978.2 Patients were matched to controls by age and geographical area. There was no statistically increased risk of fetal loss among the group as a whole. However, there was an increased risk of fetal loss in women undergoing a general anaesthetic, which was most marked for women undergoing general anaesthesia for obstetric or gynaecological procedures. Some of these obstetric procedures were cervical cerclages, procedures to prevent recurrent fetal loss, and some bias will therefore have resulted. The study did not differentiate between fetal loss at different stages of pregnancy, did not look at prematurity and did not control for coexisting illness, parity or smoking.\nMazze and K\u00e4ll\u00e9n et al.3 analysed outcomes of 5405 Swedish women who had undergone surgery during pregnancy between 1973 and 1981 (during which period there were a total of 720,000 births in Sweden). There was no increase in rates of congenital malformations or stillbirth; however, there were significant increases in death within 7 days of delivery and in prematurity.\nThe other Swedish studies involved subsets of the original data \u2013 specifically investigating appendicectomy4 and laparoscopic surgery (here the data were expanded to include 2,015,000 deliveries from 1973 to 1993).5 Sixteen per cent of women undergoing appendectomy after 24 weeks\u2019 gestation delivered on the day of their operation, with 22% delivering within 1 week. This resulted in a significant increase in prematurity and death within 7 days of delivery, but not in stillbirth.\nA systematic review of the literature from 1966 to 2002 identified 54 papers, involving a total of 12,452 patients.6 The miscarriage rate among patients undergoing surgery during pregnancy was 5.8% (10.5% if surgery took place in the first trimester); stillbirth occurred in approximately 2% of surgeries and premature delivery in 8.2%. There were, however, no controls for comparison. The clearest data (although still poorly controlled) exist for appendicitis, with surgery-induced delivery occurring in 4.6% of women undergoing appendectomy and stillbirth in 2.6%, compared with 1.2% for other surgical procedures (p\u2009<\u20090.001). Fetal loss in the presence of peritonitis was 10.9%, which suggests that the condition itself rather than the operation may lead to fetal harm.\nThere are a number of problems with the currently available evidence. It all dates back 20\u201340 years and is therefore unlikely to be representative of current outcomes given the improvements in anaesthetic drugs, surgical techniques and neonatal care. Furthermore, the Swedish data4,5 were collected with the aim of studying births and, therefore, patients who miscarry, the largest group of adverse birth outcomes, are unrecorded in these studies. The studies are also, in general, poorly controlled and have conflicting results regarding the risk of surgery. Duncan et al.2 suggest that surgery is associated with an increased risk of fetal loss (including miscarriage), and the Swedish studies4,5 suggest that there is no increase in stillbirth but that there is an increase in prematurity and early neonatal death, particularly in the case of appendectomy. Furthermore, although it is clear from the data on appendectomy that the risk to the fetus when a pregnant woman undergoes surgery is not uniform, there have been few attempts to quantify the risk by other types of surgery.\nNonetheless, of the evidence that is available, none relates directly to NHS outcomes, and there is no current NHS policy regarding carrying out non-obstetric surgery in pregnant women.\nThe project had three main objectives:\nto carry out a descriptive analysis of the data, describing counts of each adverse outcome by year, maternal age, procedure type, socioeconomic status and trimester of pregnancy\nto calculate the absolute risk and the relative odds of each adverse outcome in those women who have undergone surgery compared with those who have not\nto independently analyse broad groups, such as elective and emergency operations, as well as common procedures such as appendectomy, cholecystectomy, specific cancer surgeries and orthopaedic surgery.", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/s5.nxml", "text": "This is the first study to report the risk of adverse birth outcomes following non-obstetric surgery during pregnancy across NHS hospitals in England. We have no means of disentangling the effect of the surgery from the effect of the underlying condition itself. We found that non-obstetric surgery during pregnancy was associated with a significantly higher risk of all the outcomes we looked at, although, because of the potential for ascertainment bias, we have some reservations over the findings associated with spontaneous abortion. The overall attributable risk of an adverse birth outcome in women who had surgery during their pregnancy compared with women who did not was generally low. We estimated that, for every 287 pregnancies in which a surgical procedure was carried out, there was one additional stillbirth; for every 31 procedures there was one additional preterm delivery; for every 25 procedures there was one additional caesarean section; for every 50 procedures there was one additional long inpatient stay; for every 39 procedures there was one additional low-birthweight baby; and for every 7692 procedures there was one additional maternal death in hospital.\nOur observational study can never attribute a causal relationship between surgery and adverse birth outcomes. However, we still believe that our findings and, in particular, the NNHs, improve on previous research, by utilising a more recent and larger data set based on UK practice, and are useful reference points for any discussion of risk with prospective patients.", "pairs": [], "interleaved": []}
+{"file": "ukhsdr0429_NBK390252/abs2.nxml", "text": "We set out to estimate the risk of adverse birth outcomes following an unrelated surgical procedure (non-obstetric surgery) during pregnancy. Using English NHS hospital administrative data, we identified 6,486,280 pregnancies in the period April 2002 to March 2012. Women had surgery in 0.7% of these pregnancies.\nWe found that having an operation was associated with a small additional risk of all adverse birth outcomes compared with not having an operation. We took into account factors including maternal age, social class and illnesses that women had during pregnancy.\nWe estimated that there was one additional preterm delivery for every 31 procedures carried out during pregnancy; one additional caesarean section for 25 procedures; one additional long inpatient stay for every 50 procedures; one additional stillbirth for every 287 procedures; and one additional low-birthweight baby for every 39 procedures. The risk of adverse birth outcomes in pregnant women undergoing non-obstetric surgery is relatively low, confirming that surgical procedures during pregnancy are generally safe.\nIt is not possible to tell whether the worse outcomes in pregnancies in which surgery was carried out were attributable to the surgery or the health problems that were being treated, and we do not know if the outcomes would have been better or worse if the surgery had not been carried out. However, we believe that our findings improve on previous research, by utilising a more recent and larger data set based on UK practices, and that they may help to inform mothers of the expected risks of having a procedure during pregnancy.", "pairs": [], "interleaved": []}