The effect of smoking during pregnancy on the incidence of low birth weight among Chinese parturients.

ABSTRACT

PIP: A retrospective case controlled study was conducted to ascertain the effects of smoking on pregnancy among 213 pregnant Chinese women. Cases were included from deliveries performed at Tsan Yuk Hospital, Hong Kong, between 1988 and 1990. 4 controls were matched for every case on the basis of age, parity, and year of delivery. Hospital incidence of smoking among pregnant women was 1.57%; there was .28% of heavy smokers among all pregnant women delivering at the hospital. The average number of cigarettes smoked per day was 9. The average age of smoker was 22.6 years. There were no statistically significant differences between controls and study participants for family income, education level, and occupational class. Small babies had been delivered in the past by 17 smoking mothers and by 13 mothers in the control group. Information on smoking, alcohol, and substance abuse was asked repeatedly on the first prenatal visit and thereafter. All were asked to stop smoking. 55% of the women provided data on the time of smoking cessation, of which 2.5% had stopped just before conception. 33% had stopped before 16 weeks, and 23% had stopped between 16 and 30 weeks. 11% stopped at 30-36 weeks, and 29.9% after 36 weeks. The remaining patients (45%) had stopped at some unknown point during the pregnancy. Study participants initiated prenatal care at a later stage of pregnancy (57%) compared with controls (23%). Body weight and prenatal weight gain were similar in both groups. There were no significant differences in prenatal complications or preterm labor between the 2 groups. The results of pregnancy outcome show that babies of smoking mothers weighed 200 gm less than babies of nonsmoking mothers. There were significantly more low birth weight babies (2500 gm) among smokers. The head circumference and supine body length were significantly smaller among the smokers. Apgar scores were similar, but the chances of being admitted to the special baby care unit were higher among smokers. Placental ratio was significantly higher in the study group.