Cnattingius S, Granath F, Petersson G, Harlow B L
Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden.
N Engl J Med. 1999 Sep 23;341(13):943-8. doi: 10.1056/NEJM199909233411303.
Previous preterm delivery and maternal smoking are associated with increased risks of preterm delivery. It is not known whether gestational age at the time of a preterm delivery is correlated with gestational age in successive preterm deliveries and whether changes in smoking habits influence the subsequent risk of preterm delivery.
We studied the associations among smoking habits, previous very preterm or moderately preterm delivery (before 32 weeks and at 32 to 36 weeks, respectively), and the risk of a subsequent very preterm or moderately preterm delivery in a population-based cohort of 243,858 women in Sweden between 1983 and 1993. The results were adjusted for covariates known to be associated with preterm delivery.
The odds ratios for very or moderately preterm delivery in a subsequent pregnancy among women with a previous very preterm delivery, as compared with women who had a previous term delivery, were 12.4 (95 percent confidence interval, 9.1 to 17.0) and 7.1 (95 percent confidence interval, 6.0 to 8.4), respectively. Among women with a previous moderately preterm delivery, the corresponding odds ratios were 2.3 (95 percent confidence interval, 1.9 to 3.0) and 5.9 (95 percent confidence interval, 5.5 to 6.3), respectively. The odds ratios for a very preterm second delivery among the women who smoked 1 to 9 cigarettes per day and those who smoked 10 or more cigarettes per day, as compared with nonsmokers, were 1.4 (95 percent confidence interval, 1.1 to 1.7) and 1.6 (95 percent confidence interval, 1.3 to 2.0), respectively. The corresponding odds ratios for moderate preterm delivery were 1.3 (95% confidence interval, 1.2 to 1.4) and 1.5 (95 percent confidence interval, 1.4 to 1.6). The women who quit smoking between pregnancies were not at increased risk for very or moderately preterm delivery, whereas the women who started to smoke in the second pregnancy had the same risk as those who continued to smoke.
The risk of a very preterm delivery in successive pregnancies is increased primarily among women with a previous very preterm delivery. Changes in smoking habits influence the risk of preterm delivery as well.
既往早产和孕妇吸烟与早产风险增加相关。尚不清楚早产时的孕周是否与连续早产的孕周相关，以及吸烟习惯的改变是否会影响后续早产风险。
我们在1983年至1993年间对瑞典243,858名女性的人群队列进行研究，分析吸烟习惯、既往极早产或中度早产（分别指孕周小于32周和32至36周）与后续极早产或中度早产风险之间的关联。对已知与早产相关的协变量进行了结果校正。
既往有极早产史的女性，与既往足月产的女性相比，后续妊娠发生极早产或中度早产的比值比分别为12.4（95%置信区间为9.1至17.0）和7.1（95%置信区间为6.0至8.4）。既往有中度早产史的女性，相应的比值比分别为2.3（95%置信区间为1.9至3.0）和5.9（95%置信区间为5.5至6.3）。与不吸烟者相比，每天吸1至9支烟和每天吸10支及以上烟的女性再次发生极早产的比值比分别为1.4（95%置信区间为1.1至1.7）和1.6（95%置信区间为1.3至2.0）。中度早产的相应比值比分别为1.3（95%置信区间为1.2至1.4）和1.5（95%置信区间为1.4至1.6）。孕期戒烟的女性发生极早产或中度早产的风险并未增加，而在第二次妊娠开始吸烟的女性与继续吸烟的女性风险相同。
连续妊娠发生极早产的风险主要在既往有极早产史的女性中增加。吸烟习惯的改变也会影响早产风险。
