Johansson Anna L V, Dickman Paul W, Kramer Michael S, Cnattingius Sven
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Epidemiology. 2009 Jul;20(4):590-7. doi: 10.1097/EDE.0b013e31819dcc6a.
Maternal smoking has repeatedly been associated with increased infant mortality rates. No study has investigated whether smoking cessation influences the risk of infant death. This study estimates infant mortality after the second pregnancy in relation to smoking behavior in both the first and the second pregnancy.
We used the Swedish Medical Birth Register to identify women who delivered their first and second singleton infants during 1983-2002. Maternal smoking during the 2 pregnancies was categorized into (1) never smoker, (2) quitter, (3) starter, and (4) persistent smoker. In the second pregnancy, 555,046 live births (of at least 22 completed gestational weeks) were followed for infant death within 1 year. Cox regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs).
Compared with infants born to never smokers, the HR (95% CI) of infant mortality in the second pregnancy was 2.0 (1.7-2.4) among infants born to persistently heavy smokers, whereas among women who stopped smoking in the second pregnancy, the HRs were 1.4 (1.0-2.0) among those who had been heavy smokers in the first pregnancy, and 1.0 (0.8-1.2) among those who had been light smokers. The association of smoking during pregnancy with infant mortality was modified by infant's age, and was strongest at 4-15 weeks after birth. The smoking effect on neonatal mortality, but not postneonatal mortality, was mediated by gestational age.
Smoking cessation reduced the risk of infant death. The smoking-related risk of neonatal mortality appears to be mediated by smoking effects on gestational age, a factor that only partly explains the association between smoking and postneonatal mortality.
孕妇吸烟一直与婴儿死亡率上升有关。尚无研究调查戒烟是否会影响婴儿死亡风险。本研究评估第二次怀孕后的婴儿死亡率与第一次和第二次怀孕时吸烟行为的关系。
我们利用瑞典医学出生登记册，确定在1983年至2002年期间分娩其第一和第二个单胎婴儿的妇女。两次怀孕期间的孕妇吸烟情况分为：（1）从不吸烟者；（2）戒烟者；（3）开始吸烟者；（4）持续吸烟者。在第二次怀孕中，对555,046例活产（至少妊娠22周）进行了为期1年的婴儿死亡随访。采用Cox回归估计风险比（HRs）及95%置信区间（CIs）。
与从不吸烟者所生婴儿相比，第二次怀孕时，持续重度吸烟者所生婴儿的婴儿死亡率HR（95%CI）为2.0（1.7 - 2.4），而在第二次怀孕时戒烟的妇女中，第一次怀孕时为重度吸烟者的HR为1.4（1.0 - 2.0），第一次怀孕时为轻度吸烟者的HR为1.0（0.8 - 1.2）。孕期吸烟与婴儿死亡率的关联因婴儿年龄而异，在出生后4 - 15周时最强。吸烟对新生儿死亡率的影响（而非对新生儿后期死亡率的影响）由胎龄介导。
戒烟可降低婴儿死亡风险。吸烟相关的新生儿死亡率风险似乎由吸烟对胎龄的影响介导，而胎龄只是部分解释了吸烟与新生儿后期死亡率之间的关联。
