EPIDEMIOLOGY OF TWINNING IN A POPULATION-BASED SAMPLE OF LIVE BIRTHS, 1997-2007 Público

Abstract

PURPOSE: Twin birth rates in the United States have increased 70% over the last three
decades. Twinning is associated with significantly increased risk of infant and maternal
morbidity and mortality. Although previous studies have examined risk factors for
twinning, most are in populations that pre-date the widespread use of fertility treatments.

METHODS: We analyzed data from the National Birth Defects Prevention Study
(NBDPS), an ongoing multi-center case control study of major birth defects in the United
States. The study population included NBDPS control mothers, a random sample of
mothers of liveborn infants without major birth defects in the study regions, who reported
gestation of twin or singleton infants. We assessed associations of twinning among
mothers that did not report any use of fertility treatments with maternal demographic
characteristics and periconceptional exposures using logistic regression to estimate
adjusted odds ratios (aOR) and 95% confidence intervals (CI).

RESULTS: Between October 1997 and December 2007, 227 (2.7%) of 8305 mothers
reported gestation of twins. Among mothers who did not report any use of fertility
treatments, 154 (1.9%) of 7936 mothers reported gestation of twins. Non-Hispanic black
mothers were more likely to report twin gestation than non-Hispanic white mothers (aOR
1.68, 95% CI: 1.10-2.55) and mothers of twins were more likely to smoke during
pregnancy (aOR 1.64, 95% CI: 1.10-2.45) than mothers of singletons. Mothers of twins
were more likely to have two or more previous live births than no previous live births
(aOR: 1.49, 95% CI: 0.95-2.32) and were less likely to report periconceptional oral
contraceptive use (aOR 0.59, 95% CI: 0.33-1.05) than mothers of singletons. Factors
such as maternal age, height, pre-pregnancy weight, education, annual household income,
and periconceptional folic acid use were not statistically significant predictors of
twinning among mothers who did not report any use of fertility treatments.
CONCLUSION: Factors such as parity, oral contraceptive use, maternal race/ethnicity,
and tobacco smoking may have an impact on the frequency of twinning among women
who do not use fertility treatments.

Table of Contents

TABLE OF CONTENTS

INTRODUCTION 1
METHODS AND MATERIALS 7
Study Population 7
Exposures of Interest 7
Outcome of Interest 9
Analysis 10
RESULTS 11
DISCUSSION 15
REFERENCES 21
APPENDIX 35

About this Master's Thesis

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• Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.

School	Rollins School of Public Health
Department	Epidemiology
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology Health Sciences, Obstetrics and Gynecology
Palavra-chave	NBDPS twinning birth defects
Committee Chair / Thesis Advisor	Drews-Botsch, Carolyn D, Emory University
Committee Members	Tinker, Sarah, CDC Jennita, Reefhuis, CDC
Partnering Agencies	CDC

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