- Previous studies have shown an increased frequency of spontaneous abortions in the pregnancy preceding a fetus or a newborn with neural tube defect (NTD) compared with a normal newborn. One explanation of this observation is the trophoblastic cell rest hypothesis put forward by Knox and Clarke, suggesting a teratogenic interaction between the developing embryo and pathological remnants of a previous pregnancy. The other explanation is that the previously lost fetus was also affected with neural tube defect. The aim of this study was to verify whether this observation is also valid for congenital cardiovascular malformations (CCVM). Demographic and obstetric data of 99 mothers (58 Jewish and 41 Bedouin) of newborns who died in the neonatal period from isolated CCVM were compared with those of 103 mothers (48 Jewish and 55 Bedouin) of newborns who died of congenital defects other than NTD and CCVM. Spontaneous abortions in the preceding pregnancy were found in 32% of the cases with CCVM compared with 14% of cases with other defects (ODs) (P = 0.0012; odds ratio = 3.1, 95% confidence interval 1.5–6.4). This significant difference was independent of maternal age and number of pregnancies or deliveries. No difference was found between Jews and Bedouins. As there is no indication in the literature that fetuses with isolated CCVM tend to be spontaneously aborted, our findings are more supportive of the trophoblastic cell rest theory.