Maternal smoking and foetal growth b interaction with foetal and maternal characteristics

Abstract: In the thesis are analyzed the combined effects of maternal characteristics and cigarettesmoking in pregnancy on foetal growth; and potential interactions with maternalanthropometry, haemoglobin levels in the three trimesters and maternal glucose metabolismin late pregnancy. Foetal growth was assessed through serial ultrasound measurementsfrom second trimester until term and by neonatal anthropometry.The study was population based and prospective. The study group consisted ofsmoking and non-smoking, healthy women, randomly selected, para 1 and 2, with termpregnancies, and their newborns (n=1339). Comparisons were made between subgroupsof smoking and non-smoking mothers with the non-smoking mothers as reference group.The effect of maternal smoking was analyzed with both univariate and multivariatemethods, with adiustments made for confounding variables.Smoking mothers had lower prepregnancy weight but equal pregnancy weight gain ascompared with non-smokers. Foetal growth retardation caused by smoking did not seem tobe modified in any way by maternal nutrition, as estimated by maternal anthropometry.Smoking mothers had lower haemoglobin values in the second half of pregnancy,indicating a greater plasma volume expansion, compared with non-smokers. However,should a smoking mother have a high haemoglobin value in late pregnancy, there was anincreased risk for foetal growth retardation. Smoking mothers also had a higher risk of adisturbed glucose metabolism, probably due to increased insulin resistance from smoking.In the newborn, smoking was found to negatively affect all anthropometric parameters in ageneral, non-selective way. Males were proportionally more affected than females. Boysborn to smoking mothers had a weight reduction of 8.2 % and a lower fat accretion of12 %, as compared with boys born to non-smokers, whereas girls, born to smokers andnon-smokers, had a weight reduction and lower fat accretion of 4.8 % and 2 %,respectively. In male foetuses a negative effect from smoking was detected already in thesecond trimester as a decrease in BPD measurements. Smoking was also found to retardfoetal growth more than placental growth, leading to a slight disproportion between placental and foetal weights.