Using standard questionnaires, 194 singleton live born mother neonate pairs (including preterm cases and term controls) were investigated by the trained field workers with cross sectional survey at the hospitals in Anqing, Anhui Province, China.

• 采用横断面调查方法 ,使用统一的调查表 ,由安庆市各县医院对入院分娩孕妇及其单胎、活产、早产和对照新生儿进行调查 ,共得到有效样本 194个母亲 -新生儿对。