M. G. J. Jahoda

Genetic amniocentesis in twin pregnancies.

Summary. Eighty‐three patients with twin pregnancies were seen at the University Hospital of Rotterdam between 1 January 1980 and 31 August 1985 for prenatal genetic studies. No abnormal karyotypes were found. Amniotic fluid was successfully obtained from both amniotic sacs in 77 patients. In two pregnancies elevated levels of alpha‐fetoprotein (AEP) were found in both sacs. One of these pregnancies was terminated and the other continued until term. One pregnancy miscarried 4 weeks after amniocentesis at 19 weeks gestation; three women were delivered between 23 and 28 weeks, 36 at between 28 and 37 weeks and 42 women after 37 weeks. The perinatal mortality rate was 55/1000 (9 of 164). These results show that genetic amniocentesis is a safe and reliable technique in twin pregnancy but the interpretation of elevated AFP levels is complicated by the fact that AFP diffuses across the amniotic membranes between the two sacs.

Spontaneous abortion rate and advanced maternal age: Consequences for prenatal diagnosis

Maternal age related and procedure-related fetal abortion rates were studied in 384 women aged 36 and over scheduled for transabdominal chorionic villus sampling (TA-CVS) at 12-14 weeks of gestation. The pre-TA-CVS abortion rate within 30 days of intake (at 6-10 weeks of gestation) rose from 1.9% at age 35-36 years to 10.9% at 40 years and older. Women entering in the 6th week of gestation had a greater probability of aborting before TA-CVS than women entering after day 48. 26 women aborted spontaneously before TA-CVS, the majority of abortions occurring at 10-12 weeks. TA-CVS was done in 346 women. 11 pregnancies were terminated because of genetic anomalies, and 8 women had spontaneous fetal loss. These findings justify delaying prenatal diagnosis in older pregnant women until 12 weeks of gestation.

CHORIONIC VILLUS SAMPLING AND MATERNO‐FETAL TRANSFUSIONS: AN IMMUNOLOGICAL PATHOGENESIS OF VASCULAR DISRUPTIVE SYNDROMES?

Experimental materno‐embryonic transfusions with serum that is immunologically active against blood group antigens cause congenital malformations in the rat embryo. In view of the possible increased incidence of vascular disruptive syndromes after chorionic villus sampling (CVS), we investigated the occurrence of materno‐fetal transfusions (MFTs) in this procedure. In 18 pregnant women experiencing two needle introductions at CVS, we looked immunohistochemically at the presence of haemoglobin A1‐containing maternal erythrocytes in the fetal circulation of the separately collected first and second chorionic villus samples. In 4 of 18 patients (22 per cent), a significant increase of maternal cells was observed in the second sample compared with the first sample, indicating the occurrence of MFT by CVS. On the rare occasion of maternal immunization against fetal antigens, a CVS‐associated MFT might provoke immunological damage to the fetus.

Effect of chorionic villus sampling on utilization of prenatal diagnosis in women of advanced maternal age

The effect of the introduction of chorionic villus sampling on the utilization rate of prenatal diagnosis in advanced maternal age was studied during the period 1 January 1985–1 January 1991. On the first of January 1985, the age limit for prenatal diagnosis in The Netherlands was lowered from 38 to 36 years of age. The overall uptake rate during the studied period increased significantly, but only because of the increased uptake rate in the group 36 and 37 years. In the maternal age group of 42 years and older, an uptake rate as low as 15.9% was established. This was mainly determined by the relatively high percentage (73.0%) of women from ethnic minorities in this age group. The number of CVS procedures increased significantly during the study period, but the utilization rate was not influenced, since the number of amniocenteses decreased accordingly. An increase in acceptability of prenatal diagnosis by women of advanced maternal age due to early testing and early termination of pregnancy could not be substantiated in the present study.

Results of 180 First Trimester Direct Chromosome Studies in Chorionic Villi

First trimester fetal chromosome analysis has been successfully carried out for 180 patients in our center. Cytogenetic studies of chorionic villi have been greatly facilitated by the observation of Brambati and Simoni (1983) that direct preparations after sampling are possible. This method is a great improvement for parents at high risk of producing offspring with anomalies, such as carriers of a translocation or an X-linked disease. Termination of pregnancy in the case of an abnormal fetal karyotype is now possible at 9 weeks instead of at 19 weeks of gestation, after the cultivation of amniotic fluid cells. We report here the results of 180 pregnancies at risk for a chromosomal anomaly or an X-linked disease, with special emphasis on unbalanced fetal translocations, the demonstration of a fragile X chromosome in villi and DNA linkage studies of a male fetus at risk for Duchenne’s muscular dystrophy.

Reproductive behaviour following spontaneous loss of a pregnancy after prenatal diagnosis

One hundred and fifty‐eight women of advanced maternal age with complete follow up who experienced spontaneous fetal loss after prenatal diagnosis were studied for reproductive behaviour as well as prenatal diagnosis in a subsequent pregnancy. A higher rate of subsequent pregnancies amongst women who experienced an early spontaneous abortion after chorionic villus sampling (CVS) was expected compared with women who lost a pregnancy later during pregnancy after amniocentesis. Of the 92 women who underwent CVS in a previous pregnancy, 57 (62%) became pregnant again. Of the 66 women who underwent amniocentesis in the pregnancy that ended in fetal loss, 34 women (52%) had a subsequent pregnancy. The cumulative incidence of subsequent pregnancies was significantly influenced by maternal age but not by parity or the method of prenatal testing. Most women who decided on a new pregnancy opted for prenatal diagnosis. There was a preference for amniocentesis if the patient had previously undergone CVS. However, the reverse was not the case.

Selective Birth in a Dyzygotic Twin Pregnancy with Discordancy for Down’s Syndrome

The discovery of a twin pregnancy by ultrasound at the intake procedure for chorionic villus sampling or amniocentesis is not unusual because of the raised incidence of dizygotic twins at increased maternal age. Since the conception of dizygotic twins is genetically a separate and unrelated event, the risk of abnormalities in each twin is independent, but additive. In advanced maternal age, the risk of chromosomal aneuploidy in one of both fetuses varies between 2 and 6% [1]. This case report discusses the early prenatal diagnosis of twins discordant for Downs syndrome.

Effect of Chorionic Villus Sampling on Utilization of Prenatal Diagnosis in Women of Advanced Maternal Age

The effect of the introduction of chorionic villus sampling on the utilization rate of prenatal diagnosis in advanced maternal age was studied during the period 1 January 1985-1 January 1991. On the first of January 1985, the age limit for prenatal diagnosis in The Netherlands was lowered from 38 to 36 years of age. The overall uptake rate during the studied period increased significantly, but only because of the increased uptake rate in the group 36 and 37 years. In the maternal age group of 42 years and older, an uptake rate as low as 15.9% was established. This was mainly determined by the relatively high percentage (73.0%) of women from ethnic minorities in this age group. The number of CVS procedures increased significantly during the study period, but the utilization rate was not influenced, since the number of amniocenteses decreased accordingly. An increase in acceptability of prenatal diagnosis by women of advanced maternal age due to early testing and early termination of pregnancy could not be substantiated in the present study.

Genetic Amniocentesis in Twin Pregnancies

Eighty-three patients with twin pregnancies were seen at the University Hospital of Rotterdam between 1 January 1980 and 31 August 1985 for prenatal genetic studies. No abnormal karyotypes were found. Amniotic fluid was successfully obtained from both amniotic sacs in 77 patients. In two pregnancies elevated levels of alpha-fetoprotein (AFP) were found in both sacs. One of these pregnancies was terminated and the other continued until term. One pregnancy miscarried 4 weeks after amniocentesis at 19 weeks gestation; three women were delivered between 23 and 28 weeks, 36 at between 28 and 37 weeks and 42 women after 37 weeks. The perinatal mortality rate was 55/1000 (9 of 164). These results show that genetic amniocentesis is a safe and reliable technique in twin pregnancy but the interpretation of elevated AFP levels is complicated by the fact that AFP diffuses across the amniotic membranes between the two sacs.