Of all index NTD cases, anencephaly and spina bifida were most frequent, making up 44.3% and 41.3%, and encephalocele represented 14.4%.

• 无脑儿、脊柱裂和脑膨出在每 1 0 0 0 0个出生儿中的患病率分别为 4 .；71、4