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Open Access Research article

Smoking in preeclamptic women is associated with higher birthweight for gestational age and lower soluble fms-like tyrosine kinase-1 levels: a nested case control study

Susan R Kahn1*, Nisha D Almeida2, Helen McNamara3, Gideon Koren5, Jacques Genest1, Mourad Dahhou4, Robert W Platt24 and Michael S Kramer24

Author Affiliations

1 Department of Medicine, McGill University, Montreal, Quebec, Canada

2 Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada

3 Department of Obstetrics and Gynecology, McGill University, Montreal, Quebec, Canada

4 Department of Pediatrics, McGill University, Montreal, Quebec, Canada

5 Motherisk Program, Hospital for Sick Children, Toronto, Ontario, Canada

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BMC Pregnancy and Childbirth 2011, 11:91  doi:10.1186/1471-2393-11-91

Published: 10 November 2011

Abstract

Background

Smoking paradoxically increases the risk of small-for-gestational-age (SGA) birth but protects against preeclampsia. Some studies have reported a "U-shaped" distribution of fetal growth in preeclamptic pregnancies, but reasons for this are unknown. We investigated whether cigarette smoking interacts with preeclampsia to affect fetal growth, and compared levels of soluble fms-like tyrosine kinase-1 (sFlt-1), a circulating anti-angiogenic protein, in preeclamptic smokers and non-smokers.

Methods

From a multicenter cohort of 5337 pregnant women, we prospectively identified 113 women who developed preeclampsia (cases) and 443 controls. Smoking exposure was assessed by self-report and maternal hair nicotine levels. Fetal growth was assessed as z-score of birthweight for gestational age (BWGA). sFlt-1 was measured in plasma samples collected at the 24-26-week visit.

Results

In linear regression, smoking and preeclampsia were each associated with lower BWGA z-scores (β = -0.29; p = 0.008, and β = -0.67; p < 0.0001), but positive interaction was observed between smoking and preeclampsia (β = +0.86; p = 0.0008) such that smoking decreased z-score by -0.29 in controls but increased it by +0.57 in preeclampsia cases. Results were robust to substituting log hair nicotine for self-reported smoking and after adjustment for confounding variables. Mean sFlt-1 levels were lower in cases with hair nicotine levels above vs. below the median (660.4 pg/ml vs. 903.5 pg/ml; p = 0.0054).

Conclusions

Maternal smoking seems to protect against preeclampsia-associated fetal growth restriction and may account, at least partly, for the U-shaped pattern of fetal growth described in preeclamptic pregnancies. Smoking may exert this effect by reducing levels of the anti-angiogenic protein sFlt-1.