Article Obstetric and perinatal outcome of 1655 ICSI and 3974 IVF singleton and 1102 ICSI and 2901 IVF twin births: a comparative analysis

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1 RBMOnline - Vol 11. No Reproductive BioMedicine Online; on web 2 June 2005 Article Obstetric and perinatal outcome of 1655 ICSI and 3974 IVF singleton and 1102 ICSI and 2901 IVF twin births: a comparative analysis Willem Ombelet started his career in infertility and IVF in 1984 in Pretoria, South Africa. Since 1987 he has been working in the Department of Obstetrics and Gynaecology in the St Jans Hospital of Genk, Belgium. He is the founder of the Genk Institute for Fertility Technology and Chairman of four Andrology in the Nineties meetings. In 1998 he obtained his PhD degree at the University of Leuven. His thesis was entitled The value of sperm morphology and other semen parameters in diagnosis and treatment of human subfertility. In 1999 he became Head of the Department, and from 2001 to 2004 he was the President of the Flemish Society of Obstetrics and Gynaecology. Dr Willem Ombelet Willem Ombelet 1,3,5, Isabelle Cadron 3, Jan Gerris 1, Petra De Sutter 1, Eugene Bosmans 3, Guy Martens 2, Gunther Ruyssinck 2, Paul Defoort 1,2, Geert Molenberghs 4, Wilfried Gyselaers 3 1 Scientific Board of the Flemish Society of Obstetrics and Gynecology; 2 SPE (Studiecentrum voor Perinatale Epidemiologie), Brussels; 3 Genk Institute for Fertility Technology, Department of Obstetrics and Gynecology, Genk; 4 Centre for Statistics, Limburgs Universitair Centrum, Diepenbeek, Belgium 5 Correspondence: willem.ombelet@pandora.be Abstract A total of 3974 IVF and 1655 ICSI singleton births and 2901 IVF and 1102 ICSI twin births were evaluated. Pregnancies after both fresh and frozen transfers were included. IVF and ICSI singleton pregnancies were very similar for most obstetric and perinatal variables. The only significant difference was a higher risk for prematurity (<37 weeks of amenorrhoea) in IVF pregnancies compared with ICSI pregnancies (12.4 versus 9.2%, OR = 1.39, 95% CI = ). For twin pregnancies, differences were not statistically different except for a higher incidence of stillbirths in the ICSI group (2.08 versus 1.03%, OR = 2.04, 95% CI = ). Intrauterine growth retardation with or without pregnancy-induced hypertension was observed more often in the ICSI group. Regression analysis of the data with correction for parity and female age showed similar results for twins. For singletons, this analysis showed similar results with the exception of low birth weight babies (<2500 g), which were also observed more often in IVF pregnancies (9.6 versus 7.9%, OR = 0.79, CI = , P = 0.03). This large case-comparative retrospective analysis showed that the obstetric outcome and perinatal health of IVF and ICSI pregnancies is comparable. Keywords: human, ICSI, IVF, obstetric outcome, perinatal outcome, pregnancy 76 Introduction Several studies have reported on the perinatal outcome of pregnancies obtained after IVF and intracytoplasmic sperm injection (ICSI). The first reports from registries with retrospectively collected data from IVF pregnancies were reassuring (National Perinatal Statistics Unit and Fertility Society of Australia, 1988; Beral et al., 1990). A few reports mentioned a statistically relevant increase in major birth defects when IVF and ICSI pregnancies were compared with the general population or a matched group of naturally conceived gestations (Bergh et al., 1999; Wennerholm et al., 2000; Hansen et al., 2002; Koivurova et al., 2002a; Strömberg et al., 2002), while other studies did not show any difference at all (Ericson and Källén, 2001; Anthony et al., 2002). Nowadays the opinion is widely held that the perinatal outcome of pregnancies resulting from assisted reproduction is substantially worse than that of pregnancies following natural conception. This is mainly attributed to a higher rate of multiple pregnancies, which in turn is associated with a higher rate of perinatal mortality and morbidity (Luke and Keith, 1992; Gissler et al., 1995; ESHRE Capri Workshop Group, 2000, 2003; Blickstein, 2003). However, several studies have suggested that even singleton pregnancies after IVF and ICSI carry a higher risk for low birth weight and prematurity when compared with naturally conceived singletons (Tan et al., 1992; Tanbo et al., 1995; Verlaenen et al., 1995; Reubinoff et al., 1997; Dhont et al. 1999; Koudstaal et al., 2000; Koivurova et al., 2002a,b;

2 Schieve et al., 2002, Helmerhorst et al., 2004; Jackson et al., 2004; McGovern et al., 2004). The reason why perinatal health problems occur more frequently in assisted reproduction pregnancies is still unknown, but could be related to different factors such as invitro technology, the medication used in assisted reproduction programmes, or the infertility itself (Lambert, 2003). With the introduction of ICSI in 1992 (Palermo et al., 1992), even severe male subfertility could be treated successfully. From the very beginning, ICSI was considered a more risky procedure. From the point of view of perinatal health, there are major differences between IVF and ICSI in both patient selection and the techniques themselves. Two types of risks are to be considered: ICSI procedure-dependent and ICSI procedure-independent risk factors (Patrizio, 1995; Bonduelle, 2003). Procedure dependent risks are caused by the procedure itself, involving the penetration of the zona pellucida and oocyte cytoplasm. Procedure-independent risks are related to the cause of infertility, leading to the use of spermatozoa that normally cannot achieve fertilization. Ludwig and Kataliniç (2003) showed that the course of pregnancy as well as the outcome after ICSI is not affected by the origin of spermatozoa and by the number of sperm in the ejaculate. On the other hand, in a prospective, well controlled, nationwide German cohort study of more than 3000 ICSI births, it was shown that the major congenital malformation rate was increased after ICSI compared with natural conception (Kataliniç et al., 2004). Obviously even more questions are raised when epididymal or testicular spermatozoa are used in men with non-obstructive azoospermia. To investigate the possible risks of IVF and ICSI on perinatal health, a case-comparative analysis was conducted to compare the perinatal outcome of all IVF and ICSI singleton and twin pregnancies in the Dutch-speaking part of Belgium (Flanders) in the period from January 1997 until December Materials and methods A retrospective study was performed by analysing the data from the Studiecentrum voor Perinatale Epidemiologie (SPE). The SPE collects data on the medical and obstetric history, and on perinatal events of each hospital delivery in Flanders of >21 weeks of gestational age or 500 g birth weight. Full co-operation of all 80 obstetrics departments in Flanders (52 55% of all deliveries in Belgium) has been established since The SPE also gathers data on a substantial percentage (70%) of the Flemish home births, which, however, number only 600 each year. The data are based on questionnaires completed by midwives, obstetricians and paediatricians in the early neonatal period. The obstetric and perinatal file registers 33 items of data per child. If the newborn is transferred to the neonatology unit, data for another 20 neonatal items are recorded. All data are sent to a data coordinator for review of errors and omissions. Correction and completion is ensured by telephone calls, additional questionnaires and, if necessary, visits to local departments. Subsequently the files are stored in a computer database. Each year, a complete analysis of the data is performed. This results in a yearly global report for the region and an individual report provided to every obstetric unit of its site-specific outcome. From 1997 onwards, a distinction was made between IVF and ICSI pregnancies. These data include pregnancies after fresh and frozen embryo transfers following IVF and ICSI procedures. Out of 430,565 births and 422,441 deliveries between 1 January 1997 and 31 December 2003, 1655 ICSI and 3974 IVF singleton and 1102 ICSI and 2901 IVF births were selected. The main outcome measures for this study were gestational age, birth weight, fetal presentation at delivery, mode of delivery, induction of labour, fetal sex, Apgar score <5 after 5 min, admission to a neonatal intensive care unit (NICU), congenital malformations, perinatal mortality and perinatal morbidity including intracranial bleeding, convulsions, need for assisted ventilation and respiratory distress syndrome. For twin deliveries, birth weight discordancy was also included. A distinction was made between normal birth weight (>2500 g), low birth weight (LBW, <2500 g) and very low birth weight (VLBW, <1500 g). With respect to gestational age, a distinction was made between term birth ( 37 weeks), preterm (<37 weeks) and extreme preterm (<32 weeks) birth. Birth weight discordance was the weight difference between the pair of twins, expressed as the percentage of the birth weight of the largest child. Three categories were made: birth weight discordance <15%, between 15 and 25% and 25%. Stillbirth is defined as the birth of a lifeless child >500 g, neonatal death is the death of a live born child >500 g within 7 days after birth. The perinatal mortality rate is the sum of stillbirths and neonatal deaths divided by the total number of live and stillbirths. Only minor and major congenital malformations, recognized during pregnancy or during hospitalization in the neonatal period, were reported. Minor and major malformations were not differentiated. Statistics The Mann Whitney U-test, a classical non-parametric test for group comparison (Lehman, 1975), was used to compare parity, duration of pregnancy, birth weight and age of the mother between IVF and ICSI singleton pregnancies and between IVF and ICSI twin pregnancies. For the statistical analysis comparing obstetric and perinatal outcome differences between IVF and ICSI pregnancies, the odds ratio, 95% confidence interval and its corresponding P-values were used. A difference at the 5% level of significance was considered the threshold of probability. The significance of the difference between ICSI and IVF in singleton and twin pregnancies was also investigated after correction for possible effects of parity and age of the mother. Multiple logistic regression models were used for this purpose. The model included an effect of the technique (IVF or ICSI), female age and parity. The effects of both parity and age on the logit scale were considered to be linear. Results Out of 430,565 births and 422,441 deliveries, 2757 (0.64%) ICSI and 6875 (1.60%) IVF births were found. 77

3 Singleton pregnancies Data on pregnancy and perinatal outcome of 1655 ICSI and 3975 IVF singleton pregnancies are summarized in Tables 1 and 2. Gestational age (P < 0.001), parity (P < 0.001), birth weight (P = 0.045) and maternal age (P = 0.002) were significantly different between both groups. For maternal age and parity, these differences were small and probably do not have major clinical importance. A significant lower mean duration of pregnancy and mean birth weight in the IVF group can be explained by a higher incidence of prematurity (<37 weeks), which was observed more frequently in the IVF group (12.4 versus 9.2%, OR = 1.39, CI = ). The incidence of severe prematurity (<32 weeks) and very low birth weight was similar in both groups. Logistic regression analysis after adjustment for parity and female age showed similar results, with the exception of low birth weight, which was significantly increased in IVF compared with ICSI pregnancies (OR = 0.79, CI = , P = 0.03). The Caesarean section rate for singleton pregnancies was 22.3 and 23.8% for ICSI and IVF subjects respectively. This difference was not significant. There was no significant difference for any of the other major outcome measures. Congenital malformations were observed in 2.2% of ICSI babies compared with 2.3% for IVF babies (difference not significant). Twin pregnancies Parity was significantly different between both groups (P = 0.008, 1.4 for ICSI, 1.5 for IVF pregnancies), but this difference seems to have no major clinical importance. As shown in Tables 3 and 4, there was no difference between the ICSI (1102 births) and IVF group (2901 births), with the exception of a significantly higher stillbirth rate in the ICSI group (2.08 versus 1.03%; OR = 2.04, CI = ). Logistic regression analysis with correction for parity and female age showed similar results. (stillbirth: OR = 1.99, CI = , P = 0.01). A detailed study of all stillbirths (Tables 5 and 6) revealed a very high incidence of cervical incompetence with or without preterm premature rupture of membranes in 16 out of 30 IVF births (53.3%), versus 11 out of 23 for ICSI (47.8%). The rate of cervical incompetence was higher in ICSI compared with IVF pregnancies (11/551 or 2.0% for ICSI versus 16/1451 or 1.1% for IVF), although this difference was not significant. Intrauterine growth retardation with or without pregnancy-induced hypertension was observed more often in the ICSI group(9/23 or 39.1% versus 4/30 or 13.3% for IVF). The birth weight discordance was not significantly different between both groups (birth weight discordance 25%: 15.8% for IVF versus 15.4% for ICSI, birth weight discordance 15 25%: 22.1% for IVF versus 19.1% for ICSI, birth weight discordance <15%: 62.2% for IVF versus 58.4% for ICSI). The mean birth weight difference between both members of a twin was 34.9 g for IVF twins and 57.6 g for ICSI twins. This difference was not statistically significant. Discussion Data registration of the obstetrical and perinatal outcome of pregnancies after assisted reproduction is crucial and should be integrated into statutory regulations or national guidelines (Templeton, 2003). According to the literature, pregnancies and births following assisted reproduction are at increased risk for perinatal health problems. The presence of a higher incidence of multiple pregnancies seems to be the most important risk factor and therefore single embryo transfer policies are promoted and introduced in many countries (Hansen et al., 2002; Schieve et al., 2002; De Neubourg and Gerris, 2003; Wennerholm, 2003; Gurgan and Demirol, 2004; Ombelet et al., 2005). However, singleton pregnancies after IVF and ICSI are also reported to carry a higher risk for cerebral palsy, premature birth, low birth weight and multiple birth defects (Hansen et al., 2002; Koivurova et al., 2002a; Schieve et al., 2002; Strömberg et al., 2002). These health problems in assisted reproduction babies seem to originate from the infertility itself and not from other possible causative factors such as ovarian stimulatory drugs and the in-vitro procedure (Lambert, 2003). ICSI was introduced in the early 1990s as a valuable treatment option in case of severe male subfertility (Palermo et al., 1992). ICSI bypasses all natural sperm selection processes and this questions the safety of this technique. One of these was a possibly higher risk of congenital abnormalities in the ICSI children compared with IVF and naturally conceived babies. In the current study, the obstetric and perinatal outcomes of IVF versus ICSI were compared in both singleton and twin pregnancies using the data of the SPE in Flanders, Belgium. Since the obstetric and perinatal outcome is strongly linked to the number of fetuses, a comparative analysis of both groups was made considering singleton and twin pregnancies separately. No major difference was found in obstetrical and/or perinatal outcome between IVF and ICSI pregnancies, with the Table 1. General data for ICSI and IVF singleton births. Data are means ± SD unless otherwise indicated. ICSI IVF P-value a 78 Births (n) Gestational age (weeks) 38.6 ± ± 2.2 <0.001 Parity 1.4 ± ± 0.8 <0.001 Birth weight (g) 3227 ± ± Maternal age (years) 32.0 ± ± a Mann Whitney U-test.

4 Table 2. Comparison of obstetric and perinatal data of 1655 ICSI and 3974 IVF singleton births (OR = odds ratio, CI = 95% confidence interval, GA = gestational age, NICU = neonatal intensive care unit, IC bleeding = intracranial bleeding, RDS = respiratory distress syndrome). ICSI IVF OR (95% CI) P-value a n % n % Obstetric data Caesarean delivery ( ) NS Induction of labour ( ) NS Breech presentation ( ) NS Perinatal data GA <32 weeks ( ) NS GA <37 weeks ( ) <0.001 Birth weight <1500 g ( ) NS Birth weight <2500 g ( ) NS Fetal sex male ( ) NS Congenital malformations ( ) NS Apgar score < ( ) NS Transfer to NICU ( ) NS Perinatal death ( ) NS Stillbirth ( ) NS Neonatal death ( ) NS Assisted ventilation ( ) NS IC bleeding ( ) NS Convulsions ( ) NS RDS ( ) NS a Mann Whitney U-test. NS = not statistically significant. Table 3. General data for ICSI and IVF twin births. Data are means ± SD unless otherwise indicated. ICSI IVF P-value Births (n) Deliveries (n) Gestational age (weeks) 35.4 ± ± 3.0 NS Parity 1.4 ± ± 0, Birth weight (g) 2317 ± ± 580 NS Maternal age (years) 31.6 ± ± 3.7 NS a Mann Whitney U-test NS = not statistically significant. 79

5 Table 4. Comparison of obstetric and perinatal data of 1102 ICSI and 2901 IVF twin births (OR = odds ratio, CI = 95% confidence interval, GA = gestational age, NICU = neonatal intensive care unit, IC bleeding = intracranial bleeding, RDS = respiratory distress syndrome). ICSI IVF OR (95% CI) P-value a n % n % Obstetric data Caesarean delivery ( ) NS Induction of labour ( ) NS Breech presentation ( ) NS Perinatal data GA <32 weeks ( ) NS GA <37 weeks ( ) NS Birth weight <1500 g ( NS Birth weight <2500 g ( ) NS Fetal sex male ( ) NS Congenital malformations ( ) NS Apgar score < ( ) NS Transfer to NICU ( ) NS Perinatal death ( ) NS Stillbirth ( ) Neonatal death ( ) NS Assisted ventilation ( ) NS IC bleeding ( ) NS Convulsions ( ) NS RDS ( ) NS a Mann Whitney U-test NS = not statistically significant. 80

6 Table 5. Detailed study of 30 (1.03%) stillbirths following IVF in Flanders during the period (Studiecentrum voor Perinatale Epidemiologie data). A = first born, B = second born, PPROM = preterm premature rupture of membranes, IUGR = intrauterine growth retardation, PIH = pregnancy-induced hypertension. Patient Gestational Birth Cause of fetal identification age (weeks) weight (g) death/obstetric complications A Cervical incompetence PPROM B Cervical incompetence PPROM A PPROM B Unknown A PIH B IUGR A Solutio placentae A Cervical incompetence PPROM A Cervical incompetence B Cervical incompetence B Unknown B Unknown A PPROM B PPROM B Cervical incompetence B IUGR A Unknown B Unknown A PPROM B PPROM A Cervical incompetence PPROM B Cervical incompetence PPROM A Congenital malformation B Congenital malformation B Unknown B Solutio placentae A Cervical incompetence A Cervical incompetence PPROM B Cervical incompetence PPROM B IUGR PIH 81

7 Table 6. Detailed study of 23 (2.08%) stillbirths following ICSI in Flanders during the period (Studiecentrum voor Perinatale Epidemiologie-data). A = first born, B = second born, PPROM = preterm premature rupture of membranes, IUGR = intrauterine growth retardation, PIH = pregnancy-induced hypertension. Patient Gestational Birth Cause of fetal identification age (weeks) weight (g) death/obstetric complications A Cervical incompetence PPROM B IUGR A Cervical incompetence PPROM B Cervical incompetence PPROM B Unknown B IUGR B Unknown B Cervical incompetence PPROM B Unknown A IUGR/twin-to-twin transfusion syndrome B IUGR/twin-to-twin transfusion syndrome A PPROM B IUGR PIH A PPROM B PPROM A Cervical incompetence PPROM B PPROM B IUGR PIH A Cervical incompetence PPROM B Cervical incompetence PPROM B IUGR/twin-to-twin transfusion syndrome B IUGR solutio placentae PIH A IUGR PIH 82 exception of more prematurity and LBW cases in IVF singletons and more stillborns in the ICSI group (Tables 1 4). A study comparing the perinatal health outcome of singletons versus twins in the present study population will be part of a forthcoming paper in which ICSI pregnancies are compared with matched naturally conceived controls. Bonduelle et al. (1994, 1995), Wisanto et al. (1995, 1997) and Wennerholm et al. (1996) were the first to compare the perinatal outcome of ICSI versus IVF pregnancies. They reported similar results in IVF and ICSI pregnancies with respect to multiple pregnancy rate, low birth weight, preterm births, congenital malformations and perinatal outcome variables. In general, most studies do not show an increased risk for major birth defects in children conceived with IVF and ICSI (Van Steirteghem, 1997, 1998). More recent reports provided less reassuring results. In a world survey of ICSI pregnancies, Tarlatzis and Bili (2000) showed similar perinatal outcome including congenital malformations for IVF versus ICSI pregnancies, although the incidence of aberrations in sex chromosomes was slightly elevated for ICSI babies. This study was unfortunately a very heterogenous registry with no possibility of controlling for validity and completeness. Much more important are the results reported by Bonduelle et al. (1998, 2002). They found a statistically significant increase in sex chromosome aberrations (de-novo chromosomal anomalies) in a large series of prenatal tests in ICSI pregnancies although no increased risk for major malformations and neonatal complications was observed in the ICSI group compared with the IVF pregnancies. A two-fold increase in major birth defects with IVF and ICSI compared with naturally conceived children was reported by Hansen et al. (2002). In this study, the major birth defect rate was similar for IVF and ICSI offspring. Major malformations were found more often after multiple gestation in a large series of 5795 IVF and ICSI children reported by Bonduelle (2003). Therefore, multiple pregnancy as such seems to be responsible for the overall increase of major malformations in assisted reproduction pregnancies. According to the results of a prospective, controlled, nationwide German cohort study of more than 3000 ICSI births, the major congenital malformation rate was increased after ICSI compared with natural conception (Kataliniç et al., 2004). According to the results of Anthony et al. (2004) on congenital malformations in 4224 children conceived after IVF, the small increase in overall congenital malformations observed in the IVF children appears to be attributable to differences in maternal characteristics and not to any aspect of the IVF procedure. In a 5-year follow-up study, Place and

8 Englert (2003) reported a similar psychomotor and intellectual development for ICSI, IVF and spontaneously conceived children. A medical follow-up study of 5-year-old ICSI children revealed no increase in growth problems compared with children born after natural conception (Bonduelle et al., 2004). Nevertheless, concerning the question of long-term problems, some data are still missing, for example data on the fertility potential of post-pubertal children born after assisted reproduction and data on children born after intrauterine insemination and hormonal treatment (Ludwig, 2004). In the present study, the congenital malformation rate was similar between ICSI and IVF children. Compared with other reports, the incidence of congenital malformations was low (between 2.1 and 3.2%, Tables 1 4). This can partly be a result of the registration by more than 400 obstetricians and neonatologists. The data are also limited to the first 7 days after birth and it is well known that some malformations (especially minor ones) may be detected later. The manner of data collection used in the present study does not allow an exact estimation of malformations, since the registry is not standardized for this item and because minor and major malformations are not differentiated. For singleton pregnancies, similar results for all investigated perinatal variables were found. Only prematurity was seen more often in the IVF births (Tables 1 and 2). This could be the explanation for the significant difference in gestational age (P < 0.001) and birth weight (P = 0.045) between the IVF and ICSI groups. After regression analysis with correction for parity and age of the mother, the risk for LBW was significantly increased in IVF compared with ICSI pregnancies (P = 0.03). Figures for severe prematurity (less than 32 weeks) and very low birth weight did not show any difference. This means that the incidence of pregnancies at high risk for severe perinatal morbidity and subsequent longterm morbidity were not different between IVF and ICSI. Although perinatal mortality was similar in both groups, all neonatal morbidity parameters (assisted ventilation, intracranial bleeding, convulsions and respiratory distress syndrome) were seen more often in the IVF group, but the differences were not significant. A possible but hypothetical explanation may be the fact that the proportion of so-called normal women is higher in the ICSI group, since severe male subfertility is the main indication for ICSI. The proportion of unexplained infertility is probably higher in the IVF group and it is possible that this particular group is at increased risk for perinatal health problems (Pandian et al., 2001). For twin pregnancies, outcome results were similar for all investigated obstetric and perinatal parameters. The single parameter showing a difference between IVF and ICSI twins was a higher incidence of stillbirth in the ICSI group. Neonatal and perinatal mortality was similar in both groups. A detailed study of all stillbirths in IVF and ICSI pregnancies in this series showed a very high rate of extreme premature birth of less than 27 weeks due to cervical incompetence and/or preterm premature rupture of membranes (Tables 5 and 6). Cervical incompetence was seen more often in the ICSI group, and a good explanation is lacking. Intrauterine growth retardation with or without pregnancy-induced hypertension was also observed more often in the ICSI group. It was reported before that there is a higher incidence of preeclampsia in women conceiving by intrauterine insemination with washed donor spermatozoa compared with intrauterine insemination with washed partner spermatozoa. This supports, indirectly, an immunological basis for pre-eclampsia. The antigenic factor would appear to be located on the sperm as opposed to the seminal fluid itself (Smith et al., 1997; Salha et al., 1999; Wang et al., 2002). Since ICSI is mostly used in cases of azoospermia or severe oligoasthenoteratozoospermia, this could be a possible explanation of this unexpected observation. Aytoz et al. (1998) investigated the effect of sperm origin and quality on the outcome of pregnancies after ICSI. They showed that in the ejaculated sperm group, the rate of intrauterine death was higher in the severely defective sperm group than in the better-quality sperm groups. On the other hand, Ludwig and Kataliniç (2003) did not find a higher risk for pre-eclampsia in azoospermic compared with oligozoospermic patients. In the future, the database will be enlarged to investigate whether this finding is really important or not, and whether it may be linked to embryo or/and patient characteristics. Until now, there has been no information on sperm quality and its effect on obstetric outcome in the database. In conclusion, the results of this retrospective casecomparative analysis showed that the perinatal outcome of IVF and ICSI pregnancies is very similar. For singleton pregnancies, a slightly higher incidence of prematurity could be observed in the IVF group. This did not result in a significantly worse outcome in terms of perinatal morbidity and mortality. The obstetric and perinatal outcome of twin pregnancies following IVF and ICSI were also comparable with the only exception of an increased stillbirth rate in the ICSI group. A detailed study of all stillbirths in both groups showed a higher incidence of pregnancy-induced hypertension and/or intrauterine growth retardation in the ICSI group. Nevertheless, it is considered that the results of this large study are reassuring with respect to the outcome of ICSI pregnancies compared with IVF pregnancies. 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