Introduction: Maternal smoking is an important modifiable risk factor for intrauterine growth restriction. Yet, many women continue to smoke throughout pregnancy. During pregnancy, the daily requirement for many micronutrients increases due to higher physiologic demands. Outside of pregnancy, the dietary intakes of smokers compare unfavourably with non-smokers but there is limited information on the dietary intakes of women continuing to smoke in pregnancy.

Objective: In this prospective study, we compared the dietary intakes of micronutrients and macronutrients at the first prenatal visit of women who reported continuing to smoke during pregnancy with the intakes of women who were non-smokers.

Methods: Women were recruited at their convenience after sonographic confirmation of an ongoing singleton pregnancy. Clinical and sociodemographic details were computerized and birth outcomes collected. Women were given a detailed dietary questionnaire to complete at the clinic and maternal folate levels were measured.

Discussion and conclusions: Of the 502 women, the mean age was 30.5 (SD5.6) years, 42.5% were nulliparas, 19.2% were obese and 398 (79.3%) completed the questionnaire satisfactorily. In the 50 (12.6%) current smokers, the micronutrients magnesium, iron, carotene and copper were lower (all p < 0.005) whereas sodium and chloride were higher compared with the 348 (87.4%) non-smokers. Smokers reported lower intakes of fibre than non-smokers (p < 0.001). Smokers also reported lower intakes of dietary folate (p = 0.006) compared with non-smokers. Only 38.0% of smokers reached the optimal red blood cell folate level associated with a lower risk of neural tube defects, compared to 71.3% of non-smokers. The dietary intakes of former smokers compared favourably with non-smokers.

We found that women who continue to smoke during pregnancy have serious dietary inadequacies which potentially may aggravate fetal growth restriction. This provides a further reason to promote smoking cessation interventions in pregnancy and highlights the need for dietary and supplementation interventions in women who continue to smoke.