Maternal smoking does not affect fetal size as measured in the mid-second trimester.
BACKGROUND
Cigarette smoking during pregnancy is causally related to birthweight, but we do not know whether fetal growth restriction is a continuous process or, if not, at what stage of pregnancy it affects weight gain.


METHODS
A random sample of para 1 and 2 mothers, drawn from the population of pregnant women in Bergen and Trondheim, Norway, and Uppsala, Sweden, were examined by a detailed questionnaire concerning smoking habits, menstrual history and pregnancy dating, and subjected to morphometric sonography of their fetuses in or around week 17. Of the 547 study participants, 31.9% were smokers. Gestational age was primarily determined by the last menstrual period [LMP], except in those with irregular cycles, and in 30 cases (6.6% of those with regular cycles) in whom the biparietal diameter [BPD]-determined age deviated >14 days from the LMP-based date.


RESULTS
The analysis did not reveal any statistically significant differences between the fetuses of non-smokers, light smokers (0-9 cigarettes per day) and heavy (10+ cigarettes per day) smokers, regarding BPD, mean abdominal diameter [MAD] femur length [FL], and a 'body contour index': [BPD+FL]/MAD.


CONCLUSIONS
Tobacco-induced fetal growth restriction probably begins after gestational week 17.
Bergsjø
Per
P
Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. per.bergsjo@fhi.no
Bakketeig
Leiv S
LS
Lindmark
Gunilla
G
D000886:Anthropometry; D005260:Female; D005269:Femur / Q000196:embryology; D047109:Fetal Development / Q000187:drug effects*; D020567:Fetal Weight / Q000187:drug effects*; D006257:Head / Q000196:embryology; D006801:Humans; D008137:Longitudinal Studies; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D012907:Smoking / Q000009:adverse effects*; D011795:Surveys and Questionnaires; D016216:Ultrasonography, Prenatal