The interplay between maternal obesity and smoking in determining birth weight at term.

Gray, S. (Sophie) (2014) The interplay between maternal obesity and smoking in determining birth weight at term. thesis, Medicine.

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Abstract

Objective To evaluate the interplay between maternal obesity and cigarette smoking at the first prenatal visit and birth weight (BW) at term. Methods We studied women with a singleton pregnancy who delivered an infant weighing ≥500 g after 37 weeks gestation during the five years 2009-2013. Clinical and sociodemographic details were computerized at the first prenatal visit and updated after delivery. Maternal weight and height were measured at the first visit by trained midwives and Body Mass Index (BMI) calculated. Smoking status was recorded and divided in non-smokers, light smokers (<10 cigarettes/day) and heavy smokers (>10 cigarettes/day). All pregnancies were dated by ultrasound. Results Of 38,491 women, the mean age was 30.8 years, 40.0% were nulliparas, 14.1% were smokers and 16.4% were obese. On multi variable linear regression analysis, mean BW increased with parity, advancing maternal age, advancing gestation, male gender, Irish nativity, obesity and non-smoking. All these seven variables added significantly to the model (p<0.001) and statistically explained 25.4% of the variability in mean BW (R²=0.254). In moderate and severely obese women smoking had a major impact on decreasing mean BW (p=<0.001 and p=0.019 respectively), but increasing BMI had minimal impact on the increase in mean BW in the moderately and severely obese (p=0.092 and p=0.729 respectively). Maternal BMI and smoking interacted on a multiplicative scale. A two-way ANOVA showed that maternal smoking effects male and female infant BW evenly (p=0.140). Conclusion In this large well-characterized obstetric population, maternal smoking and increased BMI influenced BW in opposite directions and interacted on a multiplicative scale. However, smoking had an effect across all BMI categories, but the influence of BMI started to plateau at 30.0 kg/m² particularly in non-smokers. Maternal smoking effects male and female infants to the same degree. In women who are obese at their first prenatal visit, smoking is a stronger determinant of infant BW than the degree of obesity.

Item Type:	Thesis (Thesis)
Supervisor name:	Dekker, Dr. K.S.
Supervisor name:	Turner, Prof. M. and UCD Centre for Human Reproduction and Coombe Women and Infants University Hospital, Dublin
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:41
Last Modified:	25 Jun 2020 10:41
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/236

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