O-51: The genetic factor in recurrent miscarriage

Abstract

1.) To assess the incidence of embryonic chromosomal aberrations in recurrent first trimester miscarriage, and subsequent prognosis. 2.) Whether parental karyotyping or pregestational screening (PGS) are valid substitutes. A computerized literature search was made of medline embase etc. using the relevant key words, and of our own database of 1800 patients. The details of publications in the literature and of our own database were entered into a computerised database, (SPSS, Chicago, Ill.). The following questionswere asked:- 1). The prevalence of fetal chromosomal aberrations. 2). Outcome of the subsequent pregnancy. 3). Was repeat fetal aneuploidy reported. 4). Outcome of subsequent pregnancy in parental chromosomal aberrations. 5). Karyotype of the abortus in the presence of parental karyotypic aberrations. 6). Live birth rate and implantation rate in PGS and recurrent miscarriage. Five studies assessed fetal karyotyping in recurrent miscarriage. The mean number of miscarriages was 4.12± 0.48. The incidence of fetal chromosomal aberrations varied between 25% - 57%, (mean 41.6% ± 13.9). The prognosis for a subsequent pregnancy was available in two series. 62.9% (51 of 81) of pregnancies terminated in live births after aneuploidic abortions compared to only 37.9% (41 of 108) after euploid abortions (OR = 2.78, CI 1.47-5.27). Two papers provide information on repeat karyotyping. Only 11 of 73 patients (15%) aborted a second aneuploid abortion. There are three series on the prognosis in parental karyotypic aberrations. There was a 47.5% live birth rate in patients with a mean of 3.7 previous miscarriages. Additionally, one series has karyotyped the abortus in the presence of parental karyotypic aberrations. 27 of 39 (69%) abortuses were chromosomally normal. Hence, parental karyotyping does not provide a diagnosis or prognosis. Two series have shown that there is an increased prevalence of chromosomal aberrations at PGS, when the embryos of women with recurrent pregnancy loss are compared to controls (63% and 45% respectively). Although two series have shown a 74% live birth rate after PGS. The pregnancy rate was only 23%. There is no substitute for karyotyping the abortus in recurrent miscarriage, as this allows a diagnosis, and accurate prognosis to be made. Parental karyotyping is a poor substitute, as it does not make a diagnosis nor does it give a prognosis. PGS is of limited value, as some patients with recurrent miscarriage, and no infertility had been converted from miscarriage to implantation failure. However, PGS has a place in certain subgroups of patient including the older patient, and pregestational diagnosis has a place in the few patients with parental chromosomal aberrations who abort chromosomally abnormal embryos, and those with repeat embryonic aneuploidy. However, the definition of these subgroups depends on accuratel determination of the fetal karyotype.