Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
Epidemiology. 2013 May;24(3):379-86. doi: 10.1097/EDE.0b013e3182873a73.
The inverse association between prenatal smoking and preeclampsia is puzzling, given the increased risks of prematurity and low birthweight associated with both smoking and preeclampsia. We analyzed the Norwegian Mother and Child Birth Cohort (MoBa) to determine whether the associations varied by timing of prenatal smoking.
We conducted an analysis of 74,439 singleton pregnancies with completed second- and third- trimester questionnaires. Active and passive smoke exposure by trimester were determined by maternal self-report, and covered the period of preconception through approximately 30 weeks' gestation. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.
Rates of active smoking declined dramatically during pregnancy: for trimester 1, 23%; trimester 2, 9%; and trimester 3, 8%. Active smoking in the third trimester was associated with reduced odds of preeclampsia and gestational hypertension, with the strongest association among continuous smokers (for preeclampsia, OR= 0.57 [95% CI = 0.46-0.70]). Women who quit smoking before the third trimester had approximately the same risk of preeclampsia and gestational hypertension as nonsmokers. There was some evidence of dose-response, with the heaviest smokers (more than eight cigarettes per day) having the lowest risks of preeclampsia (0.48 [0.32-0.73]) and gestational hypertension (0.51 [0.28-0.95]). There was little evidence of an association with passive smoking exposure.
The association between smoking and preeclampsia varies substantially according to the timing and intensity of exposure. A better understanding of the biologic pathways that underlie these associations may provide important clues to the etiology of preeclampsia and the development of effective clinical interventions.
鉴于吸烟和子痫前期都与早产和低出生体重的风险增加有关，因此产前吸烟与子痫前期之间呈负相关令人费解。我们分析了挪威母婴队列研究（MoBa），以确定产前吸烟的时间是否会影响这些关联。
我们对 74439 例完成了第二和第三孕期问卷的单胎妊娠进行了分析。通过母亲自我报告确定了每个孕期的主动和被动吸烟暴露情况，并涵盖了受孕前到大约 30 周妊娠的时间。计算了调整后的比值比（OR）和 95%置信区间（CI）。
怀孕期间主动吸烟的比例急剧下降：第一孕期为 23%，第二孕期为 9%，第三孕期为 8%。第三孕期主动吸烟与子痫前期和妊娠高血压的发病风险降低相关，其中连续吸烟者的关联最强（子痫前期的 OR=0.57 [95%CI=0.46-0.70]）。在第三孕期之前戒烟的女性患子痫前期和妊娠高血压的风险与不吸烟者大致相同。有一些证据表明存在剂量反应，吸烟量最大的（每天超过 8 支烟）患子痫前期（0.48 [0.32-0.73]）和妊娠高血压（0.51 [0.28-0.95]）的风险最低。被动吸烟暴露与子痫前期之间几乎没有关联。
吸烟与子痫前期之间的关联根据暴露的时间和强度而有很大差异。对这些关联背后的生物学途径有更好的理解可能为子痫前期的病因学和有效临床干预措施的发展提供重要线索。
