***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To evaluate whether baseline or procedural stress during  in vitro fertilization ( IVF ) or gamete intrafallopian transfer ( GIFT )  affects pregnancy or live birth delivery rates . DESIGN Prospect i ve study . SETTING Seven clinics in Southern California between 1993 and 1998 . PATIENT(S ) One hundred and fifty-one women completed two question naires . INTERVENTION(S ) None . MAIN OUTCOME MEASURE(S ) The number of oocytes aspirated and fertilized , the number of embryos transferred , the achievement of a pregnancy , live birth delivery , and infant outcomes . RESULT ( S ) Positive-affect negative-affect score at baseline negatively influenced the number of oocytes retrieved and embryos transferred . A higher expectation of pregnancy was associated with greater numbers of oocytes fertilized and embryos transferred . At baseline , the risk of no live birth was 93 % lower for women who had the highest positive-affect score compared to those with the lowest score . Furthermore , the score on the Infertility Reaction Scale was related to negative outcomes in live birth delivery , infant birth weight , and multiple births . During the time of the procedure , the PANAS and Bipolar Profile of Moods States results were related to the number of oocytes fertilized and embryos transferred ; stress did not affect pregnancy or delivery . CONCLUSION ( S ) Baseline ( acute and chronic ) stress affected biologic end points ( i.e. , number of oocytes retrieved and fertilized ) , as well as pregnancy , live birth delivery , birth weight , and multiple gestations , whereas ( procedural ) stress only influenced biologic end points In a case-control study an association was found between mothers ' smoking habits and the frequency of dizygotic twinning .  As cases were included all twins born in Denmark in 1984 and 1985 . A r and om sample of 1.5 % of mothers to singletons , born in the same period were selected as controls . Only live-borns  , conceived after no hormonal treatment  , were included in the study . The finding may be due to the well-known anti-estrogen effect of smoking In the present study we investigated the effect of a woman 's smoking status on the quality of the oocyte , zygote , and on day 3 pre-embryo , as well as the likelihood of achieving an ongoing pregnancy at 8 weeks . Smokers presented a higher number of nonfertilized oocytes than nonsmokers ( 20.1 % vs. 10.8 % of fertilization failure ) , by comparable clinical pregnancy rate for smokers ( 40.8 % ; 28/72 ) and for nonsmokers ( 39.2 % ; 23/58 ) We investigated whether cigarette smoking , measured by follicular fluid concentrations of cotinine ( a major metabolite of nicotine ) , affects the maturity of oocytes from women undergoing in-vitro fertilization ( IVF ) and embryo transfer . In 234 women , follicular fluid sample s were assessed for cotinine and their 2020 oocytes were assessed for maturity stage . Data on individual proportions of oocytes which were mature ( OM ) and were fertilized ( OF ) were analysed by regression in relation to age and follicular fluid cotinine . OF gave an independent assessment of oocyte maturity . Both age and follicular fluid cotinine entered the OM and OF regressions and were significant . The age-adjusted regression coefficients for log cotinine were positive ; greater cotinine concentrations usually accompanied greater OM and OF . The cotinine effect on OM was positive in younger women , but it became negative ( decreased OM with increasing cotinine concentrations ) in older women ( > or = 40 years ) . We further found in older women an average reduction of approximately 50 % in the number of mature oocytes ; this reduced number was lower than the number of embryos usually transferred . Smoking can reduce the number of mature oocytes even further , therefore risking a negative IVF-embryo transfer outcome . This may be the reason why the negative effects of smoking become clinical ly detectable in older women OBJECTIVE This study determines whether smoking influences ovarian vascularization which thus may impair follicular development . DESIGN Prospect i ve laboratory study of follicular fluids and granulosa cells from patients undergoing in vitro fertilization . SETTING University Hospital Aachen , Germany . PATIENT(S ) Fifty smoking women and 50 nonsmoking women . INTERVENTION(S ) Cultivation of human granulosa cells . Cultivation of human umbilical vein endothelial cells ( HUVECs ) with either granulosa cell-conditioned medium or follicular fluid . Determination of clinical parameters . MAIN OUTCOME MEASURE(S ) Quantification of soluble vascular endothelial growth factor receptor 1 ( sVEGFR-1 ) and cotinine . RESULT ( S ) Mean sVEGFR-1 concentration in follicular fluid of smokers was 499.6 pg/mL compared with 159.2 pg/mL in nonsmokers . Correspondingly , supernatant of HUVECs cultured with follicular fluid from smoking and nonsmoking women showed , respectively , 1,174.1 pg/mL versus 794.2 pg/mL sVEGFR-1 . The HUVECs incubated with conditioned medium from smokers ' granulosa cells at culturing days 5 , 9 , 13 , and 17 secreted , respectively , 1,712.4 , 1,560.6 , 1,619.0 , and 1,635.0 pg/mL sVEGFR-1 , whereas nonsmokers showed , respectively , 1,147.6 , 1,067.2 , 1,135.9 , and 1,206.3 pg/mL sVEGFR-1 . Mean cotinine concentration in smoking women was 83.9 ng/mL and in nonsmoking was 2.8 ng/mL. In all four comparisons , differences between groups reached statistical significance . CONCLUSION ( S ) This study showed that smokers secrete significantly higher amounts of sVEGFR-1 than nonsmokers , which may result in decreased ovarian vascularization and reduced oocyte maturation A prospect i ve cohort study of 222 consecutive couples undergoing 297 cycles of in-vitro fertilization and embryo transfer ( IVF-ET ) was conducted to evaluate the impact of cigarette smoking in males and females . Compared with non-smokers , females smoking at the time of treatment had more previous pregnancies ( 1.16 versus 0.63 , P less than 0.001 ) , consumed more coffee per day ( 3.29 versus 1.85 cups , P = 0.001 ) and were less likely to hold a professional or skilled job ( 41 % versus 66 % ) . There was no difference in the response to ovarian stimulation in terms of the duration and dose of human menopausal gonadotrophin , peak oestradiol level or number of oocytes retrieved . The fertilization rate was actually higher in heavy smokers than in non-smokers ( 79.3 % versus 61.3 % , P = 0.007 ) . The rate of embryo cleavage was retarded in a dose-dependent fashion . In smokers of 1 - 14 cigarettes/day , the likelihood of transferring an embryo at greater than or equal to 4-cell stage was 0.87 [ 95 % confidence limits ( CL ) 0.56 - 1.4 ] and in smokers of greater than or equal to 15 cigarettes/day , the likelihood was 0.52 ( 95 % CL 0.31 - 0.88 ) . However , evaluation of interrelated factors using logistic regression suggested that a low socioeconomic status had a greater detrimental effect on embryo cleavage rate than female smoking . No significant difference was noted in the clinical outcome following embryo transfer . A study of larger sample size is required to evaluate whether the effects of cigarette smoking are independent of socioeconomic status and other related factors and whether they result in reduced ongoing clinical pregnancy and live birth rates The aim of the present study was to evaluate consequences of cigarette smoking on male gametes . In this prospect i ve study , sperm parameters such as sperm density , motility , viability and normal morphology were measured according to the WHO criteria . In addition to these st and ard parameters , we analysed the degree of DNA fragmentation in spermatozoa using the TUNEL-assay with flow cytometry detection in 57 non-smokers and 51 smokers seeking for infertility counselling . The smoking intoxication was assessed by question naire and measured with the CO-Tester . We show that smokers ' spermatozoa have a significantly higher DNA fragmentation than non-smokers ( 32 % versus 25.9 % , p<0.01 ) . In contrast there is no significant difference in conventional parameters between smokers and non-smokers . The degree of sperm DNA fragmentation is not significantly correlated with any of the conventional parameters . These findings suggest that cigarette smoking may have deleterious effects on sperm nuclear quality and that sperm DNA fragmentation can therefore be considered as an independent parameter with diagnostic , prognostic , and strategic value in the treatment of infertility Purpose : The aim of the present study was to investigate the influence of smoking on different parameters such as oocyte count , embryo score , and basal hormone values within the scope of in vitro fertilization – embryo transfer ( IVF-ET ) . Methods : Eight hundred thirty-four women undergoing IVF-ET treatment were classified as smokers or nonsmokers on the basis of question naires . Additionally , we divided them into three groups according to their stimulation protocol —“combined stimulation ” [ I ; clomiphene citrate plus human menopausal gonadotropin ( hMG ) ] , “ ultrashort ” [ II ; gonadotropin releasing hormone agonist ( GnRHa ) plus hMG or follicle-stimulating hormone ( FSH ) ] , and “ long downregulation protocol ” (III)— and further classified again as smokers or nonsmokers within the groups . Results : In general , smoking patients were significantly ( P = 0.0195 ) younger than nonsmokers and showed a significantly ( P = 0.0379 ) lower embryo score and a tendency ( P = 0.0931 ) to produce fewer oocytes . There was no significant difference concerning the number of normally or pathologically fertilized and transfered oocytes and embryos suitable for cryopreservation . Women who smoked had significantly ( P = 0.0112 ) higher basal 17-β-estradiol ( E2 ) , luteinizing hormone ( LH ) ( P = 0.0001 ) , and dehydroepi and rosteronesulfate ( DHEAS ) ( P = 0.0039 ) levels , but their basal human prolactin ( HPRL ) levels were significantly ( P = 0.0033 ) lower than those of nonsmokers . According to the stimulation protocol used , we found the following results . Smoking patients in group I showed a significantly ( P = 0.023 ) lower embryo score and produced fewer oocytes ( P = 0.0113 ) , with fewer of them being fertilized ( P = 0.0072 ) and transferred ( P = 0.0067 ) . Women who smoked had significantly ( P = 0.0002 ) higher basal LH levels , but their HPRL levels were significantly ( P = 0.031 ) lower than those of nonsmokers . Furthermore , they had a thinner endometrium on the day of embryo transfer ( P = 0.0366 ) . In group II we measured significantly elevated basal E2levels ( P = 0.0089 ) and higher LH values ( P = 0.0092 ) in smokers . Group III showed a trend ( P = 0.0565 ) toward lower HPRL values in smokers . Conclusions : Although the fertilization rate of oocytes and the pregnancy rate were not significantly different between smokers and nonsmokers , we found significantly alterated hormonal parameters and negatively influenced oocyte parameters , particularly after clomiphene stimulation . So we might consider using only GnRHa protocol s for smoking patients . Additionally , we advise our patients to stop smoking before an IVF-ET treatment because of the complex effects of smoking on the reproductive and hormonal system BACKGROUND No information exists in the literature regarding the factors affecting the blood flow towards the endometrial and subendometrial regions during IVF treatment . METHODS We examined the effect of women 's age , their smoking habits , their type of infertility ( i.e. primary or secondary ) and parity , causes of infertility and serum estradiol ( E2 ) concentration on endometrial and subendometrial blood flows as measured by a three-dimensional ( 3D ) power Doppler ultrasound during  IVF  treatment . All patients received a st and ard long protocol of ovarian stimulation and serum E2 concentration was determined on the day of hCG . 3D ultrasound examination with power Doppler was performed on the day of oocyte collection to determine vascularization index ( VI ) , flow index ( FI ) and vascularization flow index ( VFI ) of endometrial and subendometrial regions . RESULTS The age of women , their smoking habits , their types of infertility and parity and causes of infertility had no effect on the endometrial and subendometrial 3D power Doppler flow indices . There was a negative correlation between serum E(2 ) concentration and end 
    Output:
    
This effect is expressed by worse in-vitro fertilization parameters in cycles performed on women with smoking habits .
Also , uterine receptiveness is significantly altered by the smoking habit .
In men , cigarette smoking reduces sperm production , increases oxidative stress , and DNA damage .
Spermatozoa from smokers have reduced fertilizing capacity , and embryos display lower implantation rates .
Even in-utero exposition to tobacco constituents leads to reduced sperm count in adult life .
SUMMARY A strong body of evidence indicates that the negative effect of cigarette smoking on fertility comprises fairly every system involved in the reproductive process .