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BACKGROUND: Preterm birth, the birth of an infant prior to 37 completed weeks of gestation, is the leading cause of perinatal morbidity and mortality. Preterm infants are at greater risk of respiratory, gastrointestinal and neurological diseases. Despite significant research in developed countries, little is known about the causes of preterm birth in many developing countries, especially China. This study investigates the association between sciodemographic data, obstetric risk factor, and preterm birth in five Maternal and Child Health hospitals in Beijing, China. METHODS AND FINDINGS: A case-control study was conducted on 1391 women with preterm birth (case group) and 1391 women with term delivery (control group), who were interviewed within 48 hours of delivery. Sixteen potential factors were investigated and statistical analysis was performed by univariate analysis and logistic regression analysis. Univariate analysis showed that 14 of the 16 factors were associated with preterm birth. Inter-pregnancy interval and inherited diseases were not risk factors. Logistic regression analysis showed that obesity (odds ratio (OR) = 3.030, 95% confidence interval (CI) 1.166-7.869), stressful life events (OR = 5.535, 95%CI 2.315-13.231), sexual activity (OR = 1.674, 95%CI 1.279-2.191), placenta previa (OR 13.577, 95%CI 2.563-71.912), gestational diabetes mellitus (OR = 3.441, 95%CI1.694-6.991), hypertensive disorder complicating pregnancy (OR = 6.034, 95%CI = 3.401-10.704), history of preterm birth (OR = 20.888, 95%CI 2.519-173.218) and reproductive abnormalities (OR = 3.049, 95%CI 1.010-9.206) were independent risk factors. Women who lived in towns and cities (OR = 0.603, 95%CI 0.430-0.846), had a balanced diet (OR = 0.533, 95%CI 0.421-0.675) and had a record of prenatal care (OR = 0.261, 95%CI 0.134-0.510) were less likely to have preterm birth. CONCLUSIONS: Obesity, stressful life events, sexual activity, placenta previa, gestational diabetes mellitus, hypertensive disorder complicating pregnancy, history of preterm birth and reproductive abnormalities are independent risk factors to preterm birth. Identification of remedial factors may inform local health and education policy.

Y-chromosome microdeletions (YCMs) have been found at a much higher rate in infertile men than fertile controls. A specific deletion in the azoospermia factor locus (AZF) at Yq11 is significantly associated with male infertility. Whether assisted reproductive technology (ART) increases the risk of YCM in ART-derived offspring remains unclear. In this study the occurrence of YCM in 199 fathers and their 228 sons (Chinese, Han ethnicity), including 85 offspring conceived by IVF, 73 by intra-cytoplasmic sperm injection (ICSI) and 70 by natural conception, was investigated. Nineteen candidate genes related to YCM were analysed by multiplex ligation-dependent probe amplification. We identified one de novo YCM from 70 naturally-conceived offspring and none from 158 ART-conceived offspring and found no statistical significance between these two groups. There was no statistically-significant difference in the detection rate of the father's Y-chromosome microdeletion group: IVF 10.7% (8/75), ICSI 3.2% (2/63), natural conception 8.2% (5/61). These results suggest that ART does not increase the risk of YCM in male offspring. [ABSTRACT FROM AUTHOR]