Prenatal diagnosis in women of advanced maternal age

In this thesis several aspects of prenatal diagnosis in women of advanced maternal age were studied. The effects of the increasing number of elderly gravidas. the lowering of the maternal age at which prenatal diagnosis became accessible and the introduction of chorionic villus sampling, were evaluated. It appeared that the number of gravidas older than 36 years has been increasing in our region by 0.3% each year since 1984. The yearly increase of women who visited our centre for prenatal diagnosis because of advanced age was higher than 0.3% because also women of 36 and 37 years are entitled to prenatal testing since 1984. Chorionic villus sampling was introduced in our department at the end of 1983. In 1984 CVS was an established method of prenatal testing. Five years later 50% of the procedures for advanced maternal age and approximately 90% of the procedures for high genetic risks consisted of CVS. In the early years of CVS most procedures were performed transcervically. Since it appeared that the fetal loss rate was lowest when sampling took place after 12 weeks. transabdominal (TA) CVS in elderly gravidas became the procedure of choice. Notv.rithstanding the fact that CVS is performed later in pregnancy than in most other centres. many women make the first visit to our centre too late in pregnancy to be allowed a choice between amniocentesis and TACVS. We have come to the conclusion that our efforts to provide information about recent developments in prenatal diagnosis to both the medical profession ~d to the future parents must continue. Information to ethnic minorities needs special attention since most of these women have a limited knowledge of increased risks for chromosomally abnormal offspring and the availability to detect these abnormalities. Furthermore, most Muslim patients are unaware of the fact that in case of an abnormal result a first trimester abortion is allowed according to the Koran Termination of pregnancy in the first trimester is thought to be less traumatic than in the second trimester. This difference. however. was not expressed by the percentage of women who became pregnant again after a genetic termination of pregnancy. Both women who had undergone a mid-trimester abortion and women who had experienced a first trimester abortion became pregnant again in approximately 40% of cases. Women who lost a pregnancy after prenatal diagnosis had been performed. conceived in approximately 60% of cases. In de latter group there was also no difference between CVS and amniocentesis. Further psychological studies are needed to establish to what extent early termination of pregnancy is less traumatic than mid-trimester abortion. The difference in reproductive behaviour between those women who experienced a spontaneous abortion and those whose abortion was induced. suggests that it might be more traumatic to decide upon the abortion of a chromosomally abnormal fetus, than it is to experience the spontaneous loss of a fetus after prenatal diagnosis. The advantage of CVS in obtaining the result early in pregnancy seems more obvious for the vast majority of women with normal test results since they can be reassured 4-6 weeks earlier than after amniocentesis. Twin pregnancies in elderly gravidas create a special problem in prenatal diagnosis. When an abnonnal result is present the !win will most likely be discordant for the abnormality. The possibility and risks of selective feticide must be discussed with the parents before an invasive procedure is undertaken. The probability that both fetuses display a trisomy 21 is too low (e.g. 0.02% in a 40-year old woman ) to justify prenatal testing. Counselling older women with a twin pregnancy should therefore include assessment of the parental attitude towards a discordant twin

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