Neural tube defects in spontaneous abortions.

Nine specimens with neural tube defects (NTDs) were ascertained in a consecutive series of spontaneous abortions in New York City, giving a rate of 10.2 per 1,000 testable embryos and fetuses. All seven successfully karyotyped abortions had a chromosome anomaly. The rate of NTDs in miscarriages in New York is only one-third the rate in miscarriages in London, and the difference is due entirely to a deficit of fetuses with normal chromosomes. Our data, together with data from three other centers, indicate that there is a strongly positive association (r = 0.96) between rates of neural tube defects in early pregnancy and at term. The implications of these findings for genetic counseling and for etiologic studies are discussed.