Incidence of Early Abortions and Ectopic Pregnancies in Assisted Reproduction

Abstract

Spontaneous abortion is the most common complication of pregnancy. The incidence of spontaneous abortion after spontaneous conception is difficult to determine because most pregnancies are lost before clinical recognition (Wilcox et al. 1988). The incidence of spontaneous abortion after natural conception has been estimated to be between 10% and 15% of all clinically recognized pregnancies (Miller et al. 1980). Cytogenetic evaluations of these spontaneous abortions have shown that 50–70% of the embryos are chromosomally abnormal (Simpson 1980). The chromosomal abnormalities largely result from errors in meiotic division during gametogenesis and result in genetically abnormal embryos. Some authors have concluded that the incidence of clinical abortion is higher in pregnancies resulting from in vitro fertilization (IVF) or even from other forms of assisted reproduction than in those with natural conceptions (Rizk et al. 1991b). Such comparisons may be complicated by the use of different definitions of pregnancy and abortion, by different methods of calculating abortion rates, and by failing to take into account the gestational age at the time of abortion.