Risks of Preterm Delivery and Small for Gestational Age Infants: Effects of Nondaily and Low-Intensity Daily Smoking During Pregnancy.
Few studies have examined the effects of nondaily smoking or low-intensity daily smoking and infant outcomes. We examined the associations between preterm delivery and small for gestational age (SGA) infants in relation to both nondaily and daily smoking.



We used population-based data on women who delivered live singleton infants using the 2009-11 Pregnancy Risk Assessment Monitoring System. Women's smoking status in the last 3 months of pregnancy was categorised as nonsmokers, quitters, nondaily smokers (<1 cigarette/day), and daily smokers. Controlling for maternal age, maternal race/ethnicity, education, marital status, prepregnancy body mass index (BMI), trimester of prenatal care entry, parity, and alcohol use, we estimated adjusted prevalence ratios (PR) for the outcomes of preterm delivery (<37 weeks' gestation) and SGA.



Of the 88 933 women, 13.1%, 1.7%, and 9.6% of the sample were quitters, nondaily smokers, and daily smokers, respectively, in the last 3 months of pregnancy. While nondaily smoking was not associated with preterm delivery, daily smoking was. However, we found no dose-response relationship with the number of cigarettes smoked per day. Risk of delivering a SGA infant was increased for both nondaily and daily smokers (PR 1.4, 95% CI 1.1, 1.8 and PR 2.0, 95% CI 1.9, 2.2 respectively).



Nondaily smoking in the last 3 months of pregnancy was associated with an increased risk of delivering a SGA infant. Pregnant women should be counselled that smoking, including nondaily and daily smoking, can adversely affect birth outcomes.
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.
Van T
VT
Tong
Office of Smoking and Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.
Lucinda J
LJ
England
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.|Oak Ridge Institute for Science and Education, Oak Ridge, TN.
Karilynn M
KM
Rockhill
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.
Denise V
DV
D'Angelo
D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007236:Infant, Small for Gestational Age; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
Smoking; dose-response; infant outcomes; nondaily smoking; pregnancy; preterm delivery; small for gestational age