1 The Fertility Clinic, University of Copenhagen, Rigshospitalet, 2100 Copenhagen Ø, 2 The Fertility Clinic, Ciconia V, 8270 Højbjerg, 3 The Fertility Clinic, Ciconia Ø, 2000 Frederiksberg, 4 The Fertility Clinic, Odense University Hospital, 5000 Odense, 5 The Fertility Clinic, Odense, 5000 Odense, 6 The Fertility Clinic, University Hospital of Copenhagen, Herlev County Hospital, 2730 Herlev, 7 The Fertility Clinic Trianglen, 2100 Copenhagen, 8 The Fertility Clinic, Brædstrup Hospital, 8740 Brædstrup, 9 The Fertility Clinic, Århus University Hospital, 8000 Århus C, 10 Danish Fertility Clinic, 2000 Frederiksberg, 11 The Fertility Clinic IVF, 2750 Ballerup, 12 The Fertility Clinic, The Private Hospital Hamlet, 2000 Frederiksberg, 13 The Fertility Clinic, City of Copenhagen, 1100 Copenhagen K, Denmark
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Abstract |
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Key words: intracytoplasmic sperm injection/malformation/obstetric outcome/pregnancy outcome/prenatal karyotypes
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Introduction |
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In contrast to earlier studies from selected centres with an extensive routine in ICSI, the present study from the Danish Fertility Society is a nationwide follow-up study. The aim of the study was to evaluate the pregnancy outcome and the health of all children born after ICSI performed in Denmark between January 1994 and July 1997.
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Materials and methods |
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The clinics reported the following laboratory data: indication for ICSI, number and date of embryo replacement (fresh or thawed embryos), number of implantations and number of fetuses with fetal heart activity. Hormone stimulation, oocyte collection, embryo culture and replacement were carried out according to the standard of each clinic. No more than three embryos were replaced.
A questionnaire regarding clinical data (pregnancy outcome, prenatal diagnosis, hospitalization during pregnancy, mode of delivery and health of the child) was sent by the clinics to the parents. The couples were asked whether or not they allowed contact to the departments where the delivery took place or where the child eventually had been treated. Except for one couple, whose child had been treated for congenital hip luxation, all parents who reported a birth defect gave their permission. In two cases of abortion (trisomy 21 and 18), the couple did not want the hospitals to be contacted, but rather to be contacted themselves. The questionnaire was sent twice to non-responders. If the couple did not answer the second request, or if they did not want to participate in the study, data from the registration of the clinics were used. For ethical reasons some of the clinics did not wish to contact 17 couples, where early ultrasound examination at the clinic had shown a missed or spontaneous abortion. Eight couples returned the questionnaire, stating that they did not wish to participate in the study, and 34 couples did not reply. In total, 665 questionnaires were answered, and the response rate was 94%.
All infants born with a gestational age of 24 weeks or more were included in the analyses concerning the obstetric and paediatric outcome.
Definitions
These were as follows:
Gestational age: calculated from the day of aspiration, which was defined as day 14 of the cycle.
Abortion: fetus with a gestational age less than 24 weeks.
Pre-eclampsia: no specific definition. Information obtained from the questionnaire.
Preterm birth: delivery before 37 weeks gestation.
Perinatal mortality: number of intrauterine or intrapartum deaths and neonatal deaths <7 days per 1000 children born with a gestational age of 24 weeks or more.
Low birth weight: less than 2500 g at birth.
Very low birth weight: less than 1500 g at birth.
Malformations: conditions registered in the International Classification of Diseases and Health Related Problems, 10th Revision (ICD-10; Danish National Board of Health, 1993), as a congenital malformation or chromosome abnormality (ICD-10: Q00Q99).
It should be noted that neonatal facial paralysis, pilonidal cyst and amniotic band syndrome do not have a specific ICD10 diagnosis, and so were classified as unspecified diagnosis.
The protocol was approved by the Central Ethical Committee in Denmark.
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Results |
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Complications to prenatal diagnosis
Five women (2.7%) reported leakage of amniotic fluid after amniocentesis. In one twin gestation without malformations, continuous amniotic fluid leakage for 8 weeks was reported, and this resulted in intrauterine deaths in week 25. One singleton with trisomy 21 died 10 days after CVS, and in one triplet gestation intrauterine death occurred in two fetuses with normal karyotypes shortly after the CVS.
Abnormal karyotypes and major malformations (gestational age <24 weeks)
In all cases where an abnormal prenatal karyotype or inherited structural chromosome aberration was reported (Table III), ejaculated spermatozoa were used. The autopsy of the fetus with an unbalanced translocation demonstrated multiple malformations. One pregnancy where prenatal diagnosis had shown a normal female karyotype, was interrupted after repeated ultrasound examinations had demonstrated oligohydramnios, hypoplasia of the lungs and bilateral dilatation of the renal pelvis and the ureters. Besides slight dilatation of the renal pelvis, no other malformations were found at autopsy. In total, six cases with major malformations were observed in all interrupted pregnancies or intrauterine deaths with a gestational age <24 weeks: one trisomy 18, two trisomy 21, one triploidy, one unbalanced translocation, and one fetus with oligohydramnios.
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Postnatal karyotyping (gestational age 24 weeks)
Six postnatal karyotypings were performed; five of these were liveborn children with a gestational age of 24 weeks, and the tests identified one case of deletion 13 and one case of trisomy 21. The age of these mothers were 30 and 34 years respectively.
Obstetric and neonatal data
Among the women who delivered, hospitalization due to haemorrhage and pre-eclampsia was reported in 17 and 54 cases respectively. The mode of delivery is shown in Table IV. Overall, Caesarean section was performed in 32.5% of all deliveries.
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The minor birth defects in liveborn children, as reported by the parents, are listed in Table VII. In the cases where epididymal spermatozoa had been used, no birth defects have been reported. The embryos of the infants with amniotic band syndrome and short tongue frenulum have been cryopreserved.
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Discussion |
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An interesting finding was that, although a prenatal test was recommended to most couples, only 28.5% of women in the present study underwent a prenatal diagnosis compared with 55% in the Belgian study (Bonduelle et al., 1996b, 1998a
). The mean age of the women in the two studies was similar. In Denmark, prenatal diagnosis is offered to women if they have a familial disposition, or if they are aged 35 years or more at the time of conception. In 1995, 11.2% of all Danish women who delivered had a prenatal genetic examination (Cytogenetic Central Registry, 1997
), and 2.4% had a chromosomal abnormality. The national data showed that 57.6% of all women aged 35 years or more underwent a prenatal test, compared with 48.5% in the present study. Without doubt, the slightly elevated risk of miscarriage in relation to prenatal test prevented many of these infertile couples from having the test performed.
An abnormal prenatal karyotype was found in seven out of 209 karyotypes (3.4%). Six were major chromosome aberrations (2.9%), and four were related to maternal age 35 years. Only one inherited structural aberration (0.5%) was found. Recently published results (Bonduelle et al., 1998a
) include 1082 prenatal diagnoses, among whom were observed 28 aberrations (2.5%). Of these, 18 [1.66%; confidence interval (CI) 1.02.7] were de-novo chromosomal aberrations, of which nine were sex chromosome abnormalities and the others were autosomal aberrations. A further 10 cases of inherited aberrations (0.92%; CI 0.41.7) were observed, of which one was unbalanced. Compared with the percentage of aberration described in the literature (Nielsen and Wohlert, 1991
; Jacobs et al., 1992
), these figures demonstrated a statistically significant increase in sex chromosome aberrations, and in structural de-novo and inherited aberrations. In contrast, no sex chromosome aberrations were identified among the 209 prenatal and six postnatal karyotypes in this study. However, this may be due to the relatively small number of prenatal tests carried out in this study.
Several studies have shown that the fertilization rate and pregnancy rate after ICSI are approximately the same as after conventional IVF (Palermo et al., 1996; Govaerts et al., 1998
; Silber, 1998
; Tarlatzis and Bili, 1998
). However, the microfertilization technique implies that the natural selection of the spermatozoa which fertilize the ovum is omitted, and as a consequence the risk of introducing a spermatozoon with a chromosome abnormality into the oocyte may be increased. Recently published studies have indicated that men with oligozoospermia have an increased risk of chromosome aberrations (Wilkins-Haug et al., 1997
; Johnson, 1998
; Tuerlings et al., 1998
). In the Belgian study (Bonduelle et al., 1996b
), the couples routinely had a karyotype carried out, and 1.9% of the fathers demonstrated a structural aberration. This was higher than the expected value of 0.5% identified from previous surveys of the general population (Nielsen and Wohlert, 1991
; Jacobs et al., 1992
), but was in accord with studies of males with infertility due to severe oligozoospermia (Johnson, 1998
; Lundin et al., 1998
). Although in Denmark only a minority of the malesat least at the start of the study periodhad undergone a chromosome analysis before ICSI, there were still no more structural inherited chromosome aberrations found compared with the Belgian group.
The gestational age for ICSI pregnancies was 39.8 weeks for singletons and 36.8 weeks for twins. This is in accord with results from another Scandinavian ICSI follow-up study (Wennerholm et al., 1996), though these authors only included births with a gestational age >28 weeks. In the present study, preterm birth occurred in only 6.1% of singletons compared with 7.6% to 9.3% in previous studies (Wennerholm et al., 1996
; Wisanto et al., 1996
; Govaerts et al., 1998
). In 1995, 4.7% of all singletons born in Denmark were delivered before 37 weeks gestation (Danish National Board of Health, 1997
). Multiple pregnancies, which in the present study were reported in 20.7% with 1% triplets, are associated with a higher risk of preterm birth, and the prematurity rate was 35% in twins and 100% in triplets. These data are comparable with the National data from 1995 (Danish National Board of Health, 1997
), where preterm births were found with frequencies of 39.9% in twins and 97.4% in triplets.
The mean birth weight for singletons (3483 g) was less than for the general population (3513 g), and low birth weight (6.7%) was more common among ICSI pregnancies than in the general population (3.7%). The higher rate of prematurity and lower birth weight for ICSI singletons may, at least partly, be caused by a lower rate of previous parity, increased maternal age and the cause of the underlying infertility. Birth weights below 2500 g in ICSI singletons were reported to occur in 5% to 10.3% of cases (Govaerts et al., 1998). On the other hand, the birth weight of twins (2568 g) and triplets (1992 g) born after ICSI are even higher than those cited in the National data from 1995 (Danish National Board of Health, 1997
) (2524 g and 1907 g respectively). Of all ICSI twins, 37.6% weighed <2500 g at birth, compared with 40.8% among the general population. This is consistent with the slightly lower frequency of preterm birth.
The frequency of Caesarean section was higher in ICSI deliveries (32.5%) compared with all deliveries in Denmark in 1995 (12.6%) (Danish National Board of Health, 1997). In ICSI pregnancies, as well as in the general population, the rate of Caesarean section increased according to the number of children born (25.6% versus 12.6% in singletons, and 58.9% versus 50.6% in multiple births). Meanwhile, other ICSI studies have reported a Caesarean section rate of 2126% in singletons and 4157% in twins (Wennerholm et al., 1996
; Wisanto et al., 1996
; Govaerts et al., 1998
), and have suggested that the high rate of Caesarean section was linked to the stress of the obstetrician.
In this study the perinatal mortalitywhich included all intrauterine or intrapartum deaths and early neonatal deaths with a gestational age of 24 weekswas 13.7 per 1000 children born, compared with a reported value of 17.1 per 1000 (Wisanto et al., 1996
); however, the latter report included all stillbirths with a gestational age of
26 weeks, and early neonatal deaths.
Whether there is an increased risk of birth defects following microfertilization has been discussed since the introduction of the technique. In the present study, major congenital malformations are conditions registered in ICD-10 with a Q00Q99 diagnosis. The Belgian group (Bonduelle et al., 1996b, 1998b
) and others (Palermo et al., 1996
; Wennerholm et al., 1996
; Tarlatzis and Bili, 1998
), defined major malformations as a condition requiring surgical correction, or causing functional repair, and they reported a frequency of major malformation of between 1.0% and 2.6%. Re-analysis of the Belgian data, which included 420 liveborn infants (Kurinczuk and Bower, 1997
), revealed that infants born after ICSI were twice as likely to have major birth defects as Western Australian infants. Meanwhile, over-reporting in the Belgian study may explain the results of the re-analysis (Bonduelle et al., 1997
; Mitchell, 1997
). When a recalculation was made of the prevalence of major malformations without cases of atrial septal defect, and which were of no clinical importance (Bonduelle et al., 1997
), a frequency of major malformations of 5.23% was found, this being not significantly higher than in the Western Australian population (3.78%; odds ratio 1.41; CI 0.912.16). As for a previous study (Kurinczuk and Bower, 1997
), we have classified all reported atrial septal defects as being a major birth defect, and found the rate of major malformations to be 2.2%. As the results of the present study primarily rely on information provided by the couples, it is reasonable to believe that major malformations were reported with a high degree of certainty, whereas minor malformations may not have been perceived as such by the parents. It is well known that malformations are discovered not only at birth but also in early childhood. Thus, as the follow-up period of the present study ranges from 1 to about 30 months, some major malformations may not be included, and this may result in under-reporting compared with the Western Birth Defects Registry in Australia (Bower et al., 1996
), which includes birth defects diagnosed in children aged up to 6 years.
The results of this study on outcome of ICSI pregnancies are in line with earlier reports, except those involving sex chromosome abnormalities, where none was found. Although many thousands of ICSI children have been born (Tarlatzis and Bili, 1998), the number of infants in reported outcome studies is still small. It remains necessary to collect data in order to obtain more precise estimates, especially with regard to the genetic risk, malformation rate and developmental outcome.
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Acknowledgments |
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Notes |
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References |
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Submitted on February 1, 1999; accepted on May 5, 1999.