The outcome of twin pregnancies after IVF

It has been suggested that the high rates of prematurity, low birth weight, perinatal morbidity and mortality in in-vitro fertilization (IVF) infants are due to the increased frequency of multiple gestations in this population. The aim of our study was to test this hypothesis by comparing the outcome of IVF twins with that of twins born after spontaneously conceived pregnancies. The perinatal outcome of 40 IVF twins was compared with that of 80 control twins, matched for maternal age, parity and ethnic origin. IVF twins had a higher rate of prematurity (P = 0.03), their mean birth weight was significantly lower (P < 0.01) and the frequency of very low birth weight infants was much higher (P < 0.003). There was no neonatal mortality in the control group, whereas four IVF twins died (P < 0.01). Neonatal morbidity was significantly greater in IVF twins (P < 0.05). Oxygen therapy and mechanical ventilation were administered more frequently to IVF twins (P < 0.007 and P < 0.05). We conclude that twins conceived by IVF are at a significantly higher risk for prematurity and associated neonatal morbidity and mortality than spontaneously conceived twins.      

Obstetric outcome of twin pregnancies after in-vitro fertilization: a matched control study in four Dutch university hospitals

In singleton pregnancies after in-vitro fertilization (IVF), increased rates of obstetric and perinatal complications have been reported. Studies that compared IVF twin pregnancies with spontaneously conceived twins have yielded conflicting results. We compared 96 IVF twin pregnancies to 96 controls after elaborate matching. The design of our study precluded matching by zygosity. The monozygosity rate was higher in the control group and this implies that beforehand the risk for a less favourable outcome in the control group was higher than in the IVF group. However, the average birthweight of the IVF children was less than that of children in the control group (P = 0.04). This was not due to more intrauterine growth retardation in the IVF group. The mean gestational age at birth was 5 days shorter in IVF than control pregnancies, and although this difference was not significant it might explain the lower birthweight in the IVF group. The discordance rate in the IVF group was significantly increased. We found no difference in perinatal mortality and morbidity. We conclude that this study provides further evidence for a different outcome of IVF twin pregnancies in comparison with spontaneously conceived twin pregnancies.     

What is the most relevant standard of success in assisted reproduction?: no single outcome measure is satisfactory when evaluating success in assisted reproduction; both twin births and singleton births should be counted as successes

The 2002 recommendation of the consensus meeting of the European Society of Human Reproduction and Embryology (ESHRE) that the outcome measure of assisted reproductive technology (ART) and non-ART should be 'singleton live birth rate' could profoundly effect the ability of infertility patients to become pregnant. We reviewed published reports and new data concerning elective single embryo transfer (eSET) vs. double embryo transfer (DET) and the outcome of twin pregnancies in the United States, as well as recommendations of other Societies concerning number of embryos to transfer and methods used to measure ART success. We found that no single outcome measure of ART is ideal. Mandatory eSET would result in 42%-70% fewer births compared to DET. Infertility treatments account for only 12% of all twin pregnancies and 4% of all premature births in the United States. Twin and singleton births due to ART do not occur earlier than spontaneously conceived twins and singletons unless they started as triplet and higher order pregnancies. Multiple outcome measures are necessary when evaluating ART success. Twin as well as singleton births should be counted as ART successes. The essential aim of infertility treatment should be a healthy low order (singleton or twin) birth.     

Safety issues in assisted reproductive technology: aetiology of health problems in singleton ART babies

The frequency of health problems in singleton assisted reproductive technologies (ART) babies is higher than in singletons from spontaneous gestations. Any of the following factors may be involved: in-vitro technology, ovarian stimulatory drugs and infertility itself. A literature review on premature birth, low birth weight, perinatal mortality and major birth defects in children conceived from infertility treatments was conducted. Only publications comparing the outcome of pregnancy in an infertile group of patients to a matched control group were selected. The analysis of the outcome of singleton pregnancies resulting from IVF versus artificial insemination, obtained with or without the use of ovarian stimulatory agents and obtained with or without the use of a semen donor, suggests that female infertility is an important risk factor. Criteria for screening at-risk infertile women have not yet been identified. Prospective studies designed to identify precisely the aetiology of health problems in singletons ART babies will have to be conducted. The absence of criteria correlating at-risk infertile women to health problems in their children does not allow a gynaecologist the opportunity to offer infertility treatments to the least susceptible patients.     

Perinatal complications of assisted reproduction

The main perinatal complications of assisted reproduction include congenital malformation, chromosomal aberrations, multiple pregnancy, and prematurity. Earlier studies and in vitro fertilization (IVF) registries showed that there was no increased incidence of congenital malformations in children conceived by IVF/intracytoplasmic sperm injection (ICSI). However, a large Australian study has found that by one year of age, the incidence of congenital malformations in IVF/ICSI children is increased in comparison with those naturally conceived. Several investigators found a slight but increased risk of chromosomal aberrations in ICSI children. Multiple pregnancy is a major cause of increased perinatal mortality due to increased incidence of both prematurity and congenital malformations. Even in singleton pregnancies conceived by assisted reproductive technologies, the risk of prematurity and newborns small for gestational age is increased. In this article, recently published work on perinatal complications associated with assisted reproductive technologies is reviewed.     

Spontaneous abortion in multiple pregnancy: focus on fetal pathology

Multiple pregnancy with its wide array of medical consequences poses an important condition during pregnancy. We performed perinatal autopsy in 49 cases of spontaneous abortion resulting from multiple pregnancies during the study period. Twenty-seven of the 44 twin pregnancies ending in miscarriage were conceived naturally, whereas 17 were conceived through assisted reproductive techniques. Each of the 5 triplet pregnancies ending in miscarriage was conceived through assisted reproductive techniques. There was a positive history of miscarriage in 22.4% of the cases. Monochorial placentation occurred more commonly in multiple pregnancies terminating with miscarriage than in multiple pregnancies without miscarriage. A fetal congenital malformation was found in 8 cases. Three of these cases were conceived through assisted reproductive techniques, and 5 were conceived naturally. Miscarriage was due to intrauterine infection in 36% of the cases. Our study confirms that spontaneous abortion is more common in multiple than in singleton pregnancies. Monochorial placentation predicted a higher fetal morbidity and mortality. In pregnancies where all fetuses were of male gender, miscarriage was more common than in pregnancies where all fetuses were female. Assisted reproductive techniques do not predispose to the development of fetal malformations.     

Is twin pregnancy necessarily an adverse outcome of assisted reproductive technologies?

It has recently been suggested that the measure of success of assisted reproductive technologies (ART) should be the birth of a singleton baby, whereas a twin pregnancy should be considered as a complication. Although the maternal and neonatal complications in twin pregnancies are significantly higher than those in singleton pregnancies, the classification of a twin pregnancy as a complication of ART is in our opinion debatable. Most twin pregnancies result in the birth of two healthy babies, with little or no complication for the mother, and only few twin pregnancies results in serious morbidity of the mother and of one or both of the children. The crux of our arguments is that one should consider those cases as poor outcomes and not a twin pregnancy per se.     

Embryo reduction and birth weight discordance in dichorionic twins

BACKGROUND: Twin birth weight discordance is associated with a poor perinatal outcome. The aim of this study was to analyse the risk factors of growth discordance among dichorionic twin pregnancies. METHODS: A cohort of 346 dichorionic twin pregnancies delivered at one perinatal centre between January 1996 and December 1999 was analysed. Two groups were created, according to the presence or absence of intra-pair birth weight discordance (n = 75 and 271 respectively). Birth weight discordance was defined as a difference of >/=20% of the weight of the heavier twin. The two groups were compared by uni- and multivariate analysis, with regard to the woman's characteristics, risk factors for growth restriction or discordance, and outcome of pregnancy. RESULTS: Pregnancies with birth weight discordance had a poor outcome compared with pregnancies without discordance, with a 4-fold increase in neonatal mortality. The rate of iatrogenic embryo reduction was significantly higher in discordant pregnancies (14.7 versus 6.6%, P = 0.03). The risk of birth weight discordance was increased with a larger starting number of embryos before reduction [20.2% (64/317), 28.6% (6/21), 57.1% (4/7) and 100% (1/1) respectively, for an initial number of two (no reduction), three, four, and five embryos, P = 0.02]. In multivariate analysis, embryo reduction was the only significant risk factor for the occurrence of birth weight discordance [adjusted odds ratio (OR) = 2.3 (1.0-5.2)]. CONCLUSIONS: Birth weight discordance carries a poor perinatal outcome. Embryo reduction is an independent risk factor for birth weight discordance in dichorionic twins. This finding emphasises the need for better control of assisted reproductive technology in order to avoid high-order multiple pregnancies.     

Comparative birth weights of singletons born after assisted reproduction and natural conception in previously infertile women

BACKGROUND: The possible interference of assisted reproduction techniques (ART) with epigenetic reprogramming during early embryo development has recently sparked renewed interest about the reported lower birth weight among infants born as a consequence of infertility treatments. However, the latter finding so far has relied on the comparison of the birth weight of infants conceived with ART to general population data. A more appropriate comparison group should involve pregnancies in infertile women after natural conception. Therefore, we compared neonatal birth weight data of infants born after various ART treatments, including intrauterine insemination (IUI), with those of previously infertile women achieving pregnancy after sexual intercourse. METHODS: Between August 1996 and March 2004 the data of all infertile women presenting in the infertility unit of the University Women's Hospital of Basel, Switzerland, were collected prospectively, adding up to 995 intact pregnancies and deliveries. The birth weight of all infants resulting from 741 singleton pregnancies were analysed with regard to the patients' characteristics, the occurrence of complications during pregnancy and the type of infertility treatment with which the pregnancies were achieved. RESULTS: Comparison of duration of pregnancy and birth weight of infants born after infertility treatment confirms a shorter pregnancy span and a lower mean birth weight in infants born after IVF and ICSI. If women with pregnancies after ART deliver before term, neonatal birth weight is significantly lower. CONCLUSIONS: There is a specific effect of ART, mainly IVF and ICSI, on both shortening the duration of pregnancy and lowering neonatal birth weight. Both these parameters seem to be interrelated consequences of some modification in the gestational process induced by the infertility treatment. Freezing and thawing of oocytes in the pronucleate stage had a lesser impact on pregnancy span and on neonatal birth weight.     

First-trimester bleeding and pregnancy outcome in singletons after assisted reproduction

BACKGROUND: First-trimester bleeding is frequent in assisted reproductive technique (ART) pregnancies. It is unknown whether first-trimester bleeding, if not ending in a spontaneous abortion, negatively influences further pregnancy outcome in ART in singletons. METHODS: Data were obtained from our ART database (1993-2002), with 1432 singleton ongoing pregnancies being included in this study. The outcome measures-second-trimester and third-trimester bleeding, preterm contraction rates, pregnancy duration, birthweight, Caesarean section rates, intrauterine growth retardation (IUGR), preterm prelabour rupture of membranes (P-PROM), neonatal intensive care unit (NICU) admission and perinatal mortality-were compared in the groups with and without first-trimester bleeding. RESULTS: Significantly more singleton pregnancies resulted from a vanishing twin in the group with first-trimester bleeding (8.7%) than in the controls (4.0%). A correlation was found between the incidence of first-trimester bleeding and the number of embryos transferred. First-trimester bleeding led to increased second-trimester [odds ratio (OR)=4.56; confidence interval (CI)=2.76-7.56] and third-trimester bleeding rates (OR=2.85; CI=1.42-5.73), P-PROM (OR=2.44; CI=1.38-4.31), preterm contractions (OR=2.27; CI=1.48-3.47) and NICU admissions (OR=1.75; CI=1.21-2.54). First-trimester bleeding increased the risk for preterm birth (OR=1.64; CI=1.05-2.55) and extreme preterm birth (OR=3.05; CI=1.12-8.31). CONCLUSIONS: First-trimester bleeding in an ongoing singleton pregnancy following ART increases the risk for pregnancy complications. The association between first-trimester bleeding, the number of embryos transferred and adverse pregnancy outcome provides a further argument in favour of single-embryo transfer.     

Increased risk of placenta previa in pregnancies following IVF/ICSI; a comparison of ART and non-ART pregnancies in the same mother

BACKGROUND: The risk of placenta previa may be increased in pregnancies conceived by assisted reproduction technology (ART). Whether the increased risk is due to factors related to the reproductive technology, or associated with maternal factors, is not known. METHODS: In a nationwide population-based study, we included 845,384 pregnancies reported to the Medical Birth Registry of Norway between 1988 and 2002 and compared the risk of placenta previa in 7568 pregnancies conceived after assisted fertilization, with the risk in naturally conceived pregnancies. To study the influence of ART more directly, we compared the risk of placenta previa between consecutive pregnancies among 1349 women who had conceived both naturally and after assisted fertilization. Odds ratios (OR), adjusted for maternal age, parity, previous Caesarean section and time interval between pregnancies were estimated using logistic regression. RESULTS: There was a six-fold higher risk of placenta previa in singleton pregnancies conceived by assisted fertilization compared with naturally conceived pregnancies [adjusted OR 5.6, 95% confidence interval (CI) 4.4-7.0]. Among mothers who had conceived both naturally and after assisted fertilization, the risk of placenta previa was nearly three-fold higher in the pregnancy following assisted fertilization (adjusted OR 2.9, 95% CI 1.4-6.1), compared with that in the naturally conceived pregnancy. CONCLUSIONS: The use of ART is associated with an increased risk of placenta previa. Our findings suggest that the increased risk may be caused by factors related to the reproductive technology.     

辅助生殖技术与自然受孕双胎妊娠结局临床分析

目的探讨辅助生殖技术受孕双胎妊娠与自然受孕双胎妊娠围生期的结局。方法回顾分析288例双胎妊娠孕妇,其中121例辅助生殖技术受孕双胎妊娠孕妇为研究组,同期自然受孕双胎孕妇167例为对照组,记录、比较两组并发症、分娩方式及围产儿结局等情况。结果研究组孕妇平均年龄高于对照组[（30．31±3．329）岁vs（28．93±4．641）岁],分娩孕周早于对照组[（35．2±4．37）周vs（36．2±3．02）周],顺产率明显低于对照组（2．48％vs11．38％）,差异均有统计学意义（P〈0．05）。研究组的胎膜早破、妊娠期高血压疾病、妊娠期贫血发生率、新生儿窒息率明显低于对照组,差异均有统计学意义（P〈0．05）。研究组晚期流产、妊娠期糖尿病、羊水过多等发生率高于对照组,但差异无统计学意义（P〉0．05）。研究组新生儿平均体重、双胎之一胎死宫内及胎儿畸形率与对照组比较,差异无统计学意义（P〉0．05）。结论辅助生殖技术受孕双胎与自然受孕双胎相比,胎膜早破、妊娠期高血压疾病及贫血发生率低,而晚期流产、妊娠期糖尿病及羊水过多发生率相对偏高,且分娩孕周早。故应加强其孕中期宫颈长度检测及早产预测,必要时行宫颈环扎术,降低晚期流产及早产率,并加强妊娠期血糖监测及膳食管理,降低妊娠期糖尿病发生率。     

Consequences of vanishing twins in IVF/ICSI pregnancies

BACKGROUND: Spontaneous reductions are a possible cause of the increased morbidity in IVF singletons. The aim of this study was to assess incidence rates of spontaneous reductions in IVF/ICSI twin pregnancies and to compare short- and long-term morbidity in survivors of a vanishing co-twin with singletons and born twins. METHODS: We identified 642 survivors of a vanishing co-twin, 5237 singletons from single gestations and 3678 twins from twin gestations. All children originated from pregnancies detected by transvaginal sonography in gestational week 8. By cross-linkage with the national registries the main endpoints were prematurity, birth weight, neurological sequelae and mortality. RESULTS: Of all IVF singletons born, 10.4% originated from a twin gestation in early pregnancy. Multiple logistic regression analyses adjusted for maternal age, parity and ICSI treatment showed for birth weight <2500 g an odds ratio (OR) of 1.7 [95% confidence interval (CI) 1.2-2.2] and for birth weight <1500 g OR 2.1 (95% CI 1.3-3.6) in singleton survivors of a vanishing twin versus singletons from single gestations; corresponding figures were seen for preterm birth. This increased risk was almost entirely due to reductions that occurred at >8 weeks gestation. We found no excess risk of neurological sequelae in survivors of a vanishing co-twin versus the singleton cohort; however, OR of cerebral palsy was 1.9 (95% CI 0.7-5.2). Furthermore, we observed a correlation between onset of spontaneous reduction, i.e. the later in pregnancy the higher the risk of neurological sequelae (r = -0.09; P = 0.02). Adjusted OR of child death within the follow-up period was 3.6 (95% CI 1.7-7.6) in the survivor versus the singleton cohort. CONCLUSIONS: One in 10 IVF singletons originates from a twin gestation. Spontaneous reductions that occur at >8 weeks gestation are one of the causes for the higher risk of adverse obstetric outcome in IVF singletons.     

Uterine artery Doppler velocimetry and the outcome of pregnancies resulting from ICSI.

BACKGROUND: An increased incidence of pregnancy complications following assisted reproduction has been reported. The use of uterine artery Doppler ultrasound may aid the prediction of such complications. METHODS: Doppler was performed at 18-24 weeks gestation in 114 singleton and 32 twin pregnancies after intracytoplasmic sperm injection (ICSI) and compared with a control group matched for age, parity and plurality. Outcome variables included gestational age at delivery, prematurity, preterm premature rupture of membrane (PPROM), birth weight, birth weight discordance of >20% in twins, small for gestational age (SGA), mode of delivery, development of pre-eclampsia and placental abruption. RESULTS: Compared with the controls, there were no significant differences concerning uterine Doppler parameters, pregnancy complications and the neonatal outcome, either in singleton or in twin pregnancies. According to Doppler results and/or risk factors by medical history, 42% of singleton ICSI and 39% of spontaneous singleton pregnancies were considered as high risk. In singletons, abnormal Doppler findings were associated with pre-eclampsia in 22% and SGA in 26% of ICSI patients, compared with 33 and 21% in controls; in contrast, 0 and 10% in ICSI and 3 and 6% in controls showed these complications but no risk factors respectively. No correlation was found between PPROM, prematurity, the rate of Caesarean section and pathological Doppler results. CONCLUSIONS: Uterine Doppler examination holds the potential to identify patients with an increased risk for developing pregnancy complications. According to our results, this risk is not elevated after ICSI treatment, therefore the decision of offering an intensified antenatal care should be based on the results of Doppler examination or risks by medical history rather than the mode of conception.     

Do placentae of term singleton pregnancies obtained by assisted reproductive technologies differ from those of spontaneously conceived pregnancies?

The study was conducted to investigate the association of placental morphological and histopathological features with term, singleton pregnancies obtained by assisted reproductive technologies (ART). The study group comprised 45 consecutive women with a singleton pregnancy, obtained by ART, who delivered at term. For each subject in the study group, the consecutive, matched-for-age-and-parity woman, with a term singleton, spontaneously conceived pregnancy served as the controls. The placentae of both groups were subject to a detailed morphological and histopathological investigation by one pathologist, who was blinded to specimen origin. Pregnancy complications, fetal weight and perinatal outcome were similar in both groups. No differences in morphological or histopathological features of the placenta were observed between the groups. Nevertheless, the placentae of the study group showed a borderline, significantly higher placental weight and placental:fetal weight ratio, and placental thickness was significantly higher. Abnormal umbilical cord insertion was significantly more prevalent in the study group. Neither the specific ART method employed, nor the infertility factor affected the results, suggesting that multiple embryo transfers and/or ovulation induction protocols may account for these differences.     

辅助生育技术与自然受孕双胎妊娠结局的临床分析

目的探讨辅助生育技术与自然受孕两种不同方式双胎妊娠的临床结局。方法回顾性分析我院2005年-2008年7月分娩的143例辅助生育技术受孕双胎孕妇（ART组）和108例自然受孕双胎孕妇（对照组）的孕期合并症、分娩方式及围产儿儿结局。结果（1）ART组孕妇平均年龄（33．1±4．0）岁,对照组为（28．2±4．0）岁,两组比较差异有极显著性（P〈0．001）。（2）不良孕产史发生率ART组高于对照组（13．7％vs3．7％）,差异有极显著性（P〈0．01）;初次产检孕周,ART组为（13．1±5．4）周,对照组为（17．4±6．9）周,ART组的孕期产检次数为（8．2±2．8）次,对照组为（6．7±3．1）,均有极显著性差异（P≤0．001）。（3）ART组分娩孕周为（35．1±2．1）周,对照组为（34．4±2．4）周,ART组34周及以上分娩率高于对照组（P〈0．05）;妊娠期高血压疾病的发生率ART组低于对照组。（4）ART组新生儿平均出生体重（2394．3±38．04）g,对照组为（2184．9±53．20）g,差异有极显著性（P=0．001）。ART组极低出生体重儿发生率低于对照组。新生儿窒息、围产儿死亡率、一胎胎死宫内、先天性畸形的发生率,两组均无显著差异。结论ART助孕双胎孕妇更加重视孕期保健,分娩孕周延长,妊娠期高血压疾病的发生率较低,ART助孕组单卵双胎的比例较低．围产儿结局与自然爱孕双胎相似．     

What is the most relevant standard of success in assisted reproduction? Singleton live births should also include preterm births

An intensive debate is ongoing in this journal concerning themost appropriate endpoint after assisted reproduction techniques.The endpoint suggested by the first authors was Birth Emphasizinga Successful Singleton at Term (BESST). We have evaluated themost appropriate endpoint from different perspectives: patients,public, health authorities, obstetric and IVF clinics. We findsingleton live birth highly relevant as an outcome parameteras multiple pregnancies are the main factor responsible forthe overall poorer obstetric and neonatal outcome in IVF pregnancies,and multiple pregnancies are mostly an avoidable iatrogeniccomplication. However, our proposal is that both preterm andterm singletons should be included since the prematurity rateis an outcome that is largely uninfluenced by the IVF clinics.In conclusion, we propose singleton live birth per cycle initiatedas the most appropriate main outcome after assisted reproduction.Prematurity should in addition be reported separately as a secondaryoutcome.     

Reduction of multifetal pregnancies to twins does not increase obstetric or perinatal risks.

Selective reduction in cases of multiple fetuses is used more often nowadays due to the increased number of multiple pregnancies resulting from assisted reproduction. In this retrospective study, we investigated whether twin pregnancies derived from fetal reduction carry a higher obstetric and perinatal risk compared to standard twin pregnancies. We found that the rate of miscarriage was 10.6% in the reduction group (n = 158) compared to 9.5% in the controls (n = 135). Mean gestational age at delivery was 35.7 weeks in the reduction group versus 35.1 weeks in the control group. Mean neonatal weight at birth was 2.260 g (800-3.750 g) in the reduction group compared to 2.240 g (540-3.360 g) in controls. Perinatal mortality rate was 49.3 per thousand after reduction and 42.0 per thousand in the control group. There was no statistically significant difference in any of the above parameters. Therefore, multifetal pregnancy reduction to twins does not appear to increase obstetric or perinatal risks.     

What is the most relevant standard of success in assisted reproduction?: challenges in measuring and reporting success rates for assisted reproductive technology treatments: what is optimal?

For assisted reproductive technology (ART) treatments, measures of success that move beyond traditional measures of pregnancy and live birth and narrow the numerator to infant outcomes with an optimal short- and long-term prognosis are needed. Hence, presentation of singleton live birth delivery rates is warranted. Twins have greatly increased risks for morbidity and mortality in comparison with singletons. Success rates based on singleton live births will more completely inform patients evaluating which ART treatment options will maximize their chance for a healthy infant. Additionally, providers who limit embryos transferred can feel they are on an even playing field in reporting their success rates. Measures of success that narrow the numerator further to exclude preterm or low birth weight singleton births might also be informative. However, the utility of such measures is less clear because the aetiologies of preterm birth and low birth weight among singletons are probably multifactorial. While it may be desirable to consider adverse outcomes such as congenital anomalies in defining treatment success, it is unfeasible to collect complete and accurate data on anomalies in current ART registries. As ART use increases, continual re-examination and critique of the manner in which success is defined and presented to the public is critical.     

Obstetric and perinatal outcome of pregnancies after intrauterine insemination.

The main aim of this study was to evaluate the obstetric and perinatal outcome of pregnancies after intrauterine insemination (IUI) with the partner's spermatozoa combined with ovarian stimulation. Information concerning the antenatal care and obstetric and perinatal outcome of IUI pregnancies (n = 111), spontaneous (n = 333) and in-vitro fertilization (IVF) (n = 333) was obtained from the Finnish Medical Birth Register (MBR). The multiple birth rate in the IUI group was 17% (19/111). Significantly less antenatal care was required by the IUI group than the IVF group. The frequency of Caesarean section was 25% for IUI singletons and 58% for IUI multiples, similar to the other groups. The mean (SD) gestational age for IUI singletons at birth was 39.5 (1.8) weeks, with a mean birth weight of 3285 (575) g, compared with 3448 (600) g in non-assisted singletons (P < 0.05). For IUI multiples the mean gestational age at birth was 36.0 (2.8) weeks and the mean birth weight was 2449 (678) g. The incidence of preterm birth, low birth weight or low Apgar scores and the need for neonatal care were similar in all groups. One case of major malformation and two perinatal deaths were recorded in the IUI group. In conclusion, IUI treatment did not appear to increase obstetric or perinatal risks compared with matched spontaneous or IVF pregnancies. Most problems were associated with patient characteristics and multiple pregnancy. Reduction of the high incidence of multiple pregnancies after assisted reproductive technology is essential to improve its outcome.