Real prevalence of neural tube defects in Japan: How many of such pregnancies have been terminated?

The vital role of folic acid is to reduce the risk of having a neonate afflicted with neural tube defects. The prevalence of neural tube defects (myelomeningocele and anencephaly) has been reported in an incomplete form over the last 40 years in Japan. We aimed to evaluate the total number of neural tube defects including those delivered or terminated, to clarify the proportion of those terminated, and to internationally compare their prevalence. Through information on >311 000 deliveries obtained from 262 hospitals/clinics for 2 years of 2014 and 2015, we identified that the rate of total neural tube defects (termination of pregnancy, live births and stillbirths) was 8.29 per 10 000 deliveries for the year 2014 and was 8.72 for 2015, which were 1.5 and 1.6 times higher than the respective values (live births and stillbirths) reported. It is also observed that the ratio of the total number of myelomeningocele (termination of pregnancy, live births, and stillbirths) to that of anencephaly was approximately 1:1.2, that a half of pregnancies afflicted with neural tube defects were terminated, and that the proportion of termination of pregnancy due to myelomeningocele and due to anencephaly was 20% and 80%, respectively. Internationally, the real prevalence of neural tube defects in Japan was comparatively high, ranking fifth among the seven developed countries. In conclusion, the real prevalence of total neural tube defects was approximately 1.5 times higher than that currently reported by the Japan Association of Obstetricians and Gynecologists.