***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    ***EXAMPLES*** 
    Input: BACKGROUND Midtrimester amniocentesis to investigate fetal karyotype carries a small risk of fetal loss . AIM To test the hypothesis that progesterone prophylaxis may reduce this . STUDY DESIGN A r and omised controlled trial comparing a short prophylactic treatment with progesterone after amniocentesis with untreated controls . RESULTS There were no differences in frequency of miscarriage , preterm delivery or neonatal outcome . CONCLUSION Prophylactic progesterone treatment after amniocentesis does not improve obstetric outcome This was a prospect i ve study in 1,492 women with singleton viable pregnancies undergoing chorion villus sampling ( CVS ) or early amniocentesis ( EA ) at 10 - 13 weeks of gestation because of advanced maternal age , parental anxiety or family history of chromosomal abnormality in the absence of parental chromosomal rearrangement . They were offered the option of having CVS or EA , or to be r and omised into one of the two tests . CVS was performed in 652 cases ( 375 by choice and 277 by r and omisation ) and EA was performed in 840 cases ( 562 by choice and 278 by r and omisation ) . Both procedures were carried out by transabdominal ultrasound-guided insertion of a needle ( 20 gauge ) using a free-h and technique . The two techniques were similar in providing a sample ( CVS 99.3 % , EA 100 % ) and in giving a non-mosaic cytogenetic result ( CVS 97.5 % , EA 97.9 % ) . Spontaneous loss ( intrauterine or neonatal death ) after EA ( total group 4.9 % , r and omised subgroup 5.8 % ) was significantly higher than after CVS ( total group 2.1 % , r and omised subgroup 1.8 % ; difference 2.8 % , 95 % CI 1.3 - 4.3 % , and difference 4 % , 95 % CI 1.3 - 6.7 % ) . The gestation at delivery and birth weight of the infants after EA and CVS were similar . In the EA group the incidence of talipes equinovarus ( 1.66 % ) was higher than in the CVS group ( 0.48 % ) , but this difference was not significant Women with single , viable pregnancies at 10 + 5 to 13 + 6 weeks , gestation who requested fetal karyotyping for maternal age , parental anxiety , or a previous history of chromosomal aberration were offered participation in this study . With a transabdominal ultrasound-guided technique , early amniocentesis ( EA ) was performed on 147 women and chorionic villus sampling ( CVS ) on 174 .  Spontaneous fetal loss occurred in 6.8 per cent in the EA group and 1.7 per cent in the CVS group . This difference was significant with a confidence interval ( CI ) of 0.6 - 9.6 per cent . There was also a significant difference in the need for repeat testing between the groups . In the EA group a repeat test was required in 19.0 per cent due to culture and sample failures , while 5.2 per cent of the women in the CVS group needed repeat testing because of ambiguous results . This prospect i ve study comparing EA and CVS shows that the risk of fetal loss is higher and repeat testing is needed more after EA OBJECTIVE To assess feasibility , effectiveness and risk of prenatal diagnosis by TA-CVS  at 13 - 14 and 15 - 20 weeks ' gestation . METHODS CVS was performed transabdominally by free-h and single needle insertion technique under continuous ultrasound visualization on 1844 pregnant women , aged 18 to 48 , at 13 to 20 weeks ' gestation , whose primary indication was chromosomal anomalies and single gene defects in 85 % and 15 % of cases , respectively Clinical follow-up of women undergoing TA-CVS at 13 to 20 weeks ' was prospect ively obtained ; the population was split in two groups of 13 - 14 ( series B ) and 15 - 20 weeks ' ( series C ) gestation . Statistical evaluation included a group of TA-CVS cases performed at 11 - 12 weeks ( series A ) . RESULTS Sampling was feasible in 98.2 % , 99.1 % and 95.8 % of cases of series A , B and C , respectively . Sampling was successful in all cases of the three series and a second insertion was required in 1.5 % , 1.3 % and 0.9 % , respectively . A trend towards lower fetal loss rate is apparent ( 1.02 % , 0.86 % , and 0.46 in series A , B , and C , respectively ) , although differences were not statistically significant . No post-procedural complications were reported for series B and C , while spotting was present in 1.8 % of cases for series A. Karyotyping was totally successful by short term culture and was also available by long term culture in 99 % of cases for series A , B and C when the amount of chorionic tissue was more than 15 mg . CONCLUSION TA-CVS appears highly effective and safe and might be offered as a valuable alternative to early as well as mid-trimester amniocentesis OBJECTIVE To evaluate the impact of operator caseload on the sampling efficiency for early and st and ard , midtrimester amniocentesis . STUDY DESIGN Prospect i ve ascertainment of genetic amniocenteses performed during 36 months , grouped into early ( 13 - 14 weeks ' gestation ) and st and ard procedures ( 15 - 20 weeks ' gestation ) . Details of each amniocentesis were recorded immediately after sampling , and pregnancy outcomes were retrieved via question naires completed by the delivering physician . Sampling efficiency was evaluated separately in the early and st and ard cohorts in relation to operator caseload . RESULTS In total , 193 and 707 patients underwent early and st and ard amniocentesis , respectively . Forty of 46 physician-operators performed < 50 total procedures during the study interval ( group A ) . When compared to operators performing > or = 50 cases ( group B , n = 6 ) , a higher rate of single-pass success was noted among group B physicians for both early and st and ard procedures ( A vs. B , early : 40/45 vs. 145/148 , P = .018 ; st and ard : 243/295 vs. 384/412 , P < .0001 ) . Logistic regression confirmed an independent effect of physician caseload on sampling efficiency and a significant interaction between physician caseload and simultaneous ultrasound guidance in predicting single-attempt success . CONCLUSION Operator caseload directly influenced sampling efficiency for both early and st and ard , midtrimester amniocentesis Objective To assess the risk of fetal loss attributable to  second-trimester amniocentesis .  Methods A cohort study was undertaken among singleton pregnant women undergoing genetic amniocentesis and controls matched prospect ively on a one-to-one basis , matched strictly for maternal age , parity , and socioeconomic status . Both groups were recruited at 15–24 weeks ' gestation and observed until delivery . The fetal loss rates of the groups were compared . Results A total of 2256 pairs were recruited to the study . After excluding those pairs lost to follow-up , those with fetal malformation , and those later proven to have major chromosomal abnormalities , 2045 matched pairs were compared by pregnancy outcomes . There were no significant differences in fetal loss rates , premature deliveries , or placental abruptions between the study and control groups ( P > .05 ) . However , this study did not have enough statistical power to identify differences of less than 1 % . Conclusion Second-trimester amniocentesis is probably not associated with a greater fetal loss rate than that of matched controls BACKGROUND Several cohort studies have shown the feasibility of early amniocentesis  ( between 11 and 13 weeks of gestation ) as an alternative to chorionic villus sampling ( CVS ) for karyotyping , but the only completed r and omised study of fetal safety showed a significant fetal-loss risk related to first-trimester amniocentesis . We assessed fetal safety in early amniocentesis and CVS . METHODS We assessed  early amniocentesis at 11 - 13 weeks gestational age compared with the fetal risk associated with CVS at 10 - 12 weeks . 1160 pregnant women were r and omly assigned one procedure ( 581 early amniocentesis , 579 CVS ) after a baseline ultrasound examination at 10 weeks ' gestation and were followed up until birth . Total fetal loss and neonatal morbidity were the primary outcome measures . Sampling success and pregnancy complications were secondary outcomes . We used a filter to increase the cell yield in the early amniotic-fluid sample s. CVS was transabdominal . FINDINGS We found a significantly increased occurrence of talipes equinovarus in the early amniocentesis group ( p < 0.01 ) , the risk of which was associated with sampling at the earliest gestational ages and with temporary leakage of amniotic fluid after sampling . Therefore , the trial was stopped early , which reduced the power of the safety study . 4.8 % ( 27 ) of fetuses in the CVS group and 5.4 % ( 30 ) in the early amniocentesis group were lost after r and omisation ( p = 0.66 ) . More detailed survival analysis did not show any significant differences in fetal loss rates . Leakage of amniotic fluid after sampling occurred significantly more frequently after early amniocentesis than after CVS ( p < 0.001 ) , but we found no other major differences in pregnancy complications . Significantly more CVS than early amniocentesis procedures were repeated or failed to produce a karyotype ( p < 0.01 ) . INTERPRETATION Even though the numbers were small , we found an association between early amniocentesis and talipes equinovarus . We believe this association to be true , since it supports a trend in a similar r and omised study . Our results show that early amniocentesis , when done with the filter technique , is associated with an abortion risk similar to CVS , although the limited size of our study population reduced the strength of this conclusion Outcome of pregnancy after amniocentesis was studied in a r and omised controlled trial of 4606 women , age-range 25 - 34 years , without known risk of genetic disease .  Spontaneous abortion rate was 1.7 % in the study group after amniocentesis and 0.7 % in the control group after ultrasound ( relative risk 2.3 ) . In the study group , increased levels of maternal serum alpha-fetoprotein before amniocentesis , perforation of the placenta during amniocentesis , and withdrawal of discoloured amniotic fluid were associated with an increased risk of spontaneous abortion . In the first six weeks after amniocentesis/ultrasound scan , amniotic fluid leakage occurred more often in the study group but there was no difference in the rate of vaginal bleeding . Frequency of postural malformations in the infants in the two groups was the same . In the study group , respiratory distress syndrome was diagnosed more often ( relative risk 2.1 ) and more babies were treated for pneumonia ( relative risk 2.5 ) Amniocentesis remains the most common prenatal diagnostic invasive procedure for fetal karyotyping . During counselling prior to this procedure miscarriage rates are often quoted as a single figure . In this review of 2924 amniocenteses  , we report that  miscarriage rates vary with the gestational age at which the procedure is performed . The total miscarriage rate was 1.0 per cent after early amniocenteses ( 11 + 0 - 14 + 6 weeks ) and 1.2 per cent after traditional mid-trimester amniocenteses ( 15 + 0 - 18 + 6 weeks ) . The rate was greatest ( 3.1 per cent ) for amniocenteses performed after 18 + 6 weeks ' gestation . The cumulative miscarriage risk increased from 0.03 per cent one week after the procedure to plateau at 1.1 per cent five weeks after the procedure . The preterm and still-birth rates following amniocenteses were similar in early and traditional mid-trimester amniocenteses but were significantly higher when amniocenteses were performed after 19 weeks ' gestation . Although the incidence of talipes equinovarus was higher after early amniocentesis compared with traditional mid-trimester amniocenteses ( 1.4 per cent versus 0.2 per cent ) , none of the affected infants required corrective surgery . We conclude that counselling for this procedure should be tailored to each unit 's unintended fetal loss rate based on cumulative rates . Such figures should be available to parents to assist them in their decision-making Up to now , no data are available comparing amniocentesis and chorionic villus sampling ( CVS ) using biopsy forceps . A series of 1313 consecutive women referred to our unit before 12 weeks of pregnancy for fetal cytogenetic analysis because of advanced maternal age , were r and omized into CVS with the use of transcervical biopsy forceps or mid-trimester amniocentesis . The diagnostic success rates of the two groups were 98 per cent and 100 per cent , and a second procedure was needed in 4.1 per cent ( 13/314 ) and in 0 . 3 per cent ( 1/358 ) , respectively . Follow-up was achieved in 98.7 per cent of the pregnancies . Postprocedure spontaneous fetal losses , until the first week after birth , in the 672 pregnancies that completed the trial accounted for 2.2 
    Output:
    
: Although the risks of pregnancy loss are relatively low , lack of adequate controls tends to underestimate the true added risk of prenatal invasive procedures