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.

Neural tube defects: Risk factors and preventive measures.

For the last 25 years, it has been proven that the occurrence or recurrence of neural tube defects can be prevented with the administration of folic acid before and early pregnancy. At present, over 80 countries in the world, except Japan, have mandated the fortification of wheat flour and/or rice with folic acid, which has resulted in a significant reduction in the prevalence of neural tube defects. In 2000, the Japanese government recommended folic acid 400 µg daily for young women of childbearing age and women who are planning to conceive. In 2002, the government started to present information about the importance of folic acid in the development of fetuses in the Mother-Child Health Booklet annually. Despite these endeavors, the prevalence of neural tube defects has remained unchanged. We discuss the risk factors of neural tube defects and propose preventive measures to decrease the number of neonates with neural tube defects. We believe that the government should implement the fortification of staple food with folic acid very soon, which will eventually decrease not only the neonatal mortality and morbidity, but also the economic burden on our health care system.