[Analysis of microcephaly and related factors among 31 902 infants of Chongqing, China].

To analyze the status of head circumference development and related factors of microcephaly among infants in Chongqing, China.We included infants aged 7-24 months who had received child health care services at a Chongqing hospital from 1 February 2010 to 1 November 2014. We collected data of sex, age, head circumference, childbirth conditions, mother's pregnancy history, infant feeding patterns, and parents' educational level. Ultimately, 31 902 infants (17 511 males and 14 391 females) were analyzed. The t-test was used to compare head circumference by sex, and logistic regression models used to analyze the related factors of microcephaly. Odds ratios (OR) and 95% confidence intervals (CI) were calculated.Among the different age groups (7-8, 9-10, 11-12, 13-18, and 19-24 months), head circumferences for males were (44.3±1.3), (45.2±1.4), (46.1±1.5), (46.8±1.4), and (47.8±1.4) cm, respectively; for females, head circumferences were (43.1±1.3), (44.1±1.3), (44.8±1.4), (45.7±1.4), and (46.7±1.3)cm, respectively. Head circumference for males were all greater than those for girls (t-values were 32.09, 27.73, 32.21, 41.66, and 32.03, respectively; P<0.001). The rate of microcephaly was 3.2% (1 025/31 902) among infants. Birth weights and fetal times were related to microcephaly in infants, with OR (95% CI) values 0.15(0.13-0.18) and 1.31(1.11-1.54), respectively. Factors including urban location, delayed birth, cesarean section, formula feeding, and mixed feeding patterns might reduce the risks of microcephaly compared with suburban location, term birth, eutocia, and breastfeeding; OR (95% CI) values were 0.60 (0.52-0.68), 0.55 (0.44-0.70), 0.76 (0.67-0.87), 0.46 (0.32-0.67), and 0.51 (0.34-0.75), respectively.Head circumference development among infants in Chongqing was satisfactory. Family environmental factors, birth conditions, and feeding patterns were found to be important factors related to microcephaly.