Spontaneous preterm birth and small for gestational age infants in women who stop smoking early in pregnancy: prospective cohort study

doi:10.1136/bmj.b1081

Published 26 March 2009, doi:10.1136/bmj.b1081
Cite this as: BMJ 2009;338:b1081

Research

Spontaneous preterm birth and small for gestational age infants in women who stop smoking early in pregnancy: prospective cohort study

Lesley M E McCowan, associate professor of obstetrics and gynaecology¹, Gustaaf A Dekker, professor of obstetrics and gynaecology⁶, Eliza Chan, research fellow¹, Alistair Stewart, statistician², Lucy C Chappell, senior lecturer in maternal and fetal medicine⁴, Misty Hunter, medical student¹, Rona Moss-Morris, professor of health psychology⁵, Robyn A North, professor in obstetric medicine³, On behalf of the SCOPE consortium

¹ Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, School of Population Health, University of Auckland, Auckland, New Zealand, ² Department of Epidemiology and Biostatistics, Faculty of Medical and Health Sciences, School of Population Health, University of Auckland, Auckland, New Zealand, ³ Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, University of Adelaide, Australia, ⁴ Division of Reproduction and Endocrinology, King’s College London, ⁵ School of Psychology, University of Southampton, ⁶ Women and Children’s Division, Lyell McEwin Hospital, University of Adelaide, Adelaide, South Australia

Correspondence to: L M E McCowan, Department of Obstetrics and Gynaecology l.mccowan{at}auckland.ac.nz

Objectives To compare pregnancy outcomes between women who stoppedsmoking in early pregnancy and those who either did not smokein pregnancy or continued to smoke.

Design Prospective cohort study.

Setting Auckland, New Zealand and Adelaide, Australia.

Participants 2504 nulliparous women participating in the Screeningfor Pregnancy Endpoints (SCOPE) study grouped by maternal smokingstatus at 15 (±1) week’s gestation.

Main outcome measures Spontaneous preterm birth and small forgestational age infants (birth weight <10th customised centile).We compared odds of these outcomes between stopped smokers andnon-smokers, and between current smokers and stopped smokers,using logistic regression, adjusting for demographic and clinicalrisk factors.

Results 80% (n=1992) of women were non-smokers, 10% (n=261)had stopped smoking, and 10% (n=251) were current smokers. Wenoted no differences in rates of spontaneous preterm birth (4%,n=88 v 4%, n=10; adjusted odds ratio 1.03, 95% confidence intervall0.49 to 2.18; P=0.66) or small for gestational age infants(10%, n=195 v 10%, n=27; 1.06, 0.67 to 1.68; P=0.8) betweennon-smokers and stopped smokers. Current smokers had higherrates of spontaneous preterm birth (10%, n=25 v 4%, n=10; 3.21,1.42 to 7.23; P=0.006) and small for gestational age infants(17%, n=42 v 10%, n=27; 1.76, 1.03 to 3.02; P=0.03) than stoppedsmokers.

Conclusion In women who stopped smoking before 15 weeks’gestation, rates of spontaneous preterm birth and small forgestational age infants did not differ from those in non-smokers,indicating that these severe adverse effects of smoking maybe reversible if smoking is stopped early in pregnancy.

© McCowan et al 2009
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
http://creativecommons.org/licenses/by-nc/2.0/

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