Objective: To investigate the influence of cigarette or sheesha smoking on first-trimester markers of Down syndrome.
Design: A prospective observational study.
Setting: Primary care centres and antenatal clinics of Maternity and Children Hospital, King Abdulaziz University Hospital and New Jeddah Clinic Hospital, Jeddah, Saudi Arabia.
Population: Women with a singleton pregnancy who were either nonsmokers (n = 1736) or cigarette smokers (n = 420) or sheesha smokers (n = 181).
Methods: Fetal nuchal translucency thickness (fetal NT), maternal serum free beta-human chorionic gonadotrophin (free beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) were measured at 11 weeks 0 days to 13 weeks 6 days of gestation in all women. Women were grouped according to smoking status, confirmed by maternal serum cotinine measurements, and analyte levels between groups were compared.
Main outcome measures: Fetal NT, maternal serum free beta-hCG, PAPP-A and cotinine measurements.
Results: Compared with nonsmoking women, fetal NT was significantly increased and free beta-hCG and PAPP-A levels were significantly decreased in both cigarette and sheesha smokers. There were significant relationships between all three markers and the number of sheeshas consumed per day.
Conclusions: Cigarette and sheesha smoking significantly affect first-trimester markers of Down syndrome (fetal NT, free beta-hCG and PAPP-A). Correction for this effect in women who smoke might improve the effectiveness of first-trimester screening for Down syndrome in these women. The underlying mechanism(s) relating smoking to the changes in first-trimester markers require further studies.