[The association between the frequency of prenatal care in childbearing aged women and risk of small for gestational age among neonatal twins in Shaanxi Province].

To explore the association between the frequency of prenatal care in childbearing aged women and risk of small for gestational age (SGA) among neonatal twins in Shaanxi Province. From July to December 2013, a total of 30 027 childbearing aged women, who were pregnant from January 2010 to November 2013 and had definite outcomes, were selected from 30 districts (counties) of Shaanxi Province by using the multi-stage random sampling method. The questionnaires with a face-to-face survey method were used to retrospectively collect demographic information, pregnancy history, lifestyle during pregnancy, disease history, nutritional supplements, and health care during pregnancy. Information on the gestational age and birth weight of the newborn were obtained by consulting the medical certificate of birth and were registered as twin A and twin B by birth order. Finally, 356 childbearing aged women and their twin babies with complete data were included in the analysis. A generalized estimation equation model was used to analyze the association between the frequency of prenatal care and the risk of SGA among neonatal twins. The age of childbearing aged women was (27.44±4.68) years old, of which 79.49% (283 women) were rural residents and 44.38% (158 women) had seven or more times prenatal care. The gestational age and birth weight were (37.64±2.51) weeks and (2 510±497) g, respectively. The prevalence of SGA was 51.40% (183/356) for twin A and 53.37% (190/356) for twin B, respectively. The prevalence of SGA was 44.30% (70/158) for twin A with seven or more times prenatal care and 42.41% (67/158) for twin B with seven or more times prenatal care, which was lower than that for twins with less than seven times prenatal care, respectively [57.07% (113/198) and 62.12% (123/198)] ( values were 0.017 and <0.001). The results of generalized estimation equation model suggested that compared to those with less than seven times prenatal care, after adjusting for parity, birth order, place of residence, maternal age, occupation, education, family wealth index, passive smoking, pregnancy-induced hypertension syndrome, folic acid, and iron supplement during perinatal period, and gender of the newborn, the (95) of risk of SGA among childbearing aged women with seven or more times prenatal care was 0.60 (0.40-0.91). Seven or more times prenatal care could reduce the risk of SGA among neonatal twins in Shanxi Province.