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 χ(2) 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.
目的： 研究妊娠高血压综合征与早产史对小于胎龄儿（SGA）风险的交互作用。 方法： 采用多阶段分层随机抽样的方法，对陕西省30个区（县）进行抽样调查，以问卷调查方式回顾性收集2010年1月至2013年11月间怀孕且怀孕结局明确的育龄妇女及其子女相关信息。计数资料采用百分比描述，计量资料采用x±s表示，率的比较采用χ(2)检验，多因素分析、相乘交互作用分析采用非条件logistic回归，以新生儿是否为SGA为因变量、妊娠高血压综合征和既往早产史为自变量纳入回归模型，同时控制相关混杂因素进行分析。在初产妇中，研究妊娠高血压综合征与SGA的关联；在经产妇中，研究妊娠高血压综合征、早产史对SGA的交互效应。 结果： 共收集25 751例育龄妇女及其生育子女，初产妇占60.55%（15 592/25 751），经产妇占39.45%（10 159/25 751），经产妇既往早产史发生率为1.89%（192/10 159）。25 751名育龄妇女妊娠高血压综合征的发生率为1.55%（400/25 751）、SGA发生率为15.49%（3 990/25 751）。在初产妇中，非条件logistic分析显示，孕期患妊娠高血压综合征者SGA的风险增加（OR=1.43，95%CI：1.02~2.00，P=0.041）。在经产妇中，妊娠高血压综合征主效应与SGA风险增加存在相关趋势（OR=1.34，95%CI：0.91~1.96，P=0.138）；既往早产史主效应（OR=1.61，95%CI：1.13~2.31，P=0.009）可增加SGA的发生风险；妊娠高血压综合征与早产史交互作用项（妊娠高血压综合征×早产史）与SGA发生风险增加相关（OR=5.93，95%CI：1.19~29.61，P=0.030）。 结论： 在初产妇中，妊娠高血压综合征会增加SGA发生风险；在经产妇中，妊娠高血压综合征也会增加SGA发生风险，妊娠高血压综合征、既往早产史对SGA的发生存在相乘交互作用。.
Keywords: History of preterm birth; Interaction; Pregnancy-induced hypertension; Small for gestational age.