Interaction between pregnancy-induced hypertension and history of preterm birth on the risk of small for gestational age / 中华流行病学杂志

ABSTRACT

Objective@#To investigate the interaction of pregnancy-induced hypertension and history of preterm birth on the risk of small for gestational age.@*Methods@#Stratified multistage random sampling method was used to choose samples from 30 districts and counties of Shaanxi province. Information on childbearing-age women with their children between January 2010 and November 2013 was retrospectively collected through face-to-face questionnaire survey. The childbearing-aged women were in pregnancy or having had definite outcomes of pregnancy. Enumeration data were described by percentage, and measurement data were described by Mean±SD, and χ2 test was used to compare the rates. Unconditional logistic regression analysis was performed to estimate the interaction between pregnancy-induced hypertension and history of preterm birth on the risk of small for gestational age, and by using small for gestational age as dependent variables, pregnancy-induced hypertension and history of preterm birth as independent variables. Confounding factors were under control. Firstly, the association between pregnancy-induced hypertension and small for gestational age has been analyzed in primiparas, secondly, interaction of pregnancy-induced hypertension and history of preterm birth on the risk of small for gestational age has been analyzed in multiparas.@*Results@#A total of 25 751 women of childbearing age and their children were recruited. 60.55% (15 592/25 751) were primiparas, 39.45% (10 159/25 751) were multiparas, the rate of history of preterm birth was 1.89% (192/10 159) for multiparas. The incidence rates of pregnancy-induced hypertension and small for gestational age were 1.55% and 15.49% in pregnant woman (400/25 751) and their newborns (3 990/25 751). Unconditioned logistic regression analysis showed that compared with woman without pregnancy-induced hypertension, primiparas with pregnancy-induced hypertension had increased risk of small for gestational age (OR=1.43, 95%CI 1.02-2.00, P=0.041). Regarding multiparas, the main effect of pregnancy-induced hypertension had a positive correlation with small for gestational age (OR=1.34, 95%CI 0.91-1.96), but there was no statistical significance (P=0.138). The main effect of history of preterm birth was positively correlated with small for gestational age (OR=1.61, 95%CI 1.13-2.31, P=0.009). The interaction term "pregnancy-induced hypertension×history of preterm birth" was positively associated with risk of small for gestational age (OR=5.93, 95%CI 1.19-29.61, P=0.030).@*Conclusions@#Pregnancy-induced hypertension was associated with increased risk for small for gestational age in both primiparas and multiparas, and history of preterm birth further increased risk for small for gestational age in pregnant women with pregnancy-induced hypertension, indicating that there was multiplication interaction between pregnancy-induced hypertension and history of preterm birth.