第三章神经管畸形畸形如果妇女怀孕3个月之内，胚胎发育时神经管闭合过程受到影响即产生胎儿脑或脊髓发育异常儿童颅脑的畸形神经管畸形（neuraltubedefects，NTDs）。
O O O B-dis I-dis I-dis I-dis I-dis B-dis I-dis O O O O O O O O O O O O O O O O O B-bod I-bod I-bod O O O O O O O O O O O O O B-sym I-sym I-sym I-sym I-sym I-sym I-sym I-sym B-sym I-sym I-sym I-sym I-sym I-sym I-sym B-dis I-dis I-dis I-dis I-dis O B-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis I-dis O B-dis I-dis I-dis I-dis O O