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Coffee and Smoking as Risk Factors of Twin Pregnancies: The Danish National Birth Cohort

Published online by Cambridge University Press:  21 February 2012

Maria M. Morales-Suárez-Varela*
Affiliation:
Unit of Public Health and Environmental Care. Department of Preventive Medicine. University of Valencia, Spain; Unit of Clinical Epidemiology, Dr. Peset University Hospital, Valencia, Spain; Research group CIBER CB06/02/0045, CIBER actions — Epidemiology and Public Health, Valencia, Spain. [email protected]
Bodil Hammer Bech
Affiliation:
The Danish Epidemiology Science Centre, University of Aarhus, Denmark.
Kaare Christensen
Affiliation:
Institute of Public Health, Epidemiology, University of Southern Denmark, Odense, Denmark.
Jorn Olsen
Affiliation:
The Danish Epidemiology Science Centre, University of Aarhus, Denmark; Department of Epidemiology, School of Public Health, University of California Los Angeles, United States of America.
*
*Address for correspondence: María Morales Suárez-Varela, Unit of Public Health and Environmental Care, Department of Preventive Medicine, University of Valencia, Avda, Vicente Andrés Estellés s/n, 46100 Burjasot, Valencia, Spain.

Abstract

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Twinning rates have changed substantially over time for reasons that are only partly known. In this study we studied smoking, coffee and alcohol intake, and their possible interaction with obesity as potential determinants of twinning rates using data from the Danish National Birth Cohort between 1996 and 2002. We identified 82,985 pregnancies: 81,954 singleton and 1031 twins. For the twins we had data to classify 121 as monozygotic, 189 dizygotic (same sex), 313 dizygotic (opposite sex) but, 408 were of the same sex but with unknown zygosity. All mothers were interviewed about their prepregnancy weight and height, coffee and alcohol intake, smoking habits, and potential confounding factors at early stages of pregnancy. We identified smoking (> 10 cigarettes/day) as a possible determinant of twinning, particularly for dizygotic twinning rates (same sex) and furthermore corroborated that obesity and the mother's age are strong correlates of twinning. Others have found coffee intake to increase twinning rates but that is not seen in these data.

Type
Articles
Copyright
Copyright © Cambridge University Press 2007