HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Erratum (v103,p1019) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tan, H. Articles by Rhoads, G. G. Search for Related Content PubMed PubMed Citation Articles by Tan, H. Articles by Rhoads, G. G. Related Collections Epidemiology/public health Preterm labor

The Association Between Fetal Sex and Preterm Birth in Twin Pregnancies

From the OMNI Research Group and Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Ottawa, Faculty of Medicine, Ottawa, Canada; School of Public Health, Central South University, Changsha, Hunan, P. R. China; and Division of Epidemiology, School of Public Health, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey.

Address reprint requests to: Dr. Shi Wu Wen, OMNI Research Group, Department of Obstetrics & Gynecology, University of Ottawa, Faculty of Medicine, 501 Smyth Road, Ottawa, Canada, K1H 8L6; e-mail: swwen{at}ohri.ca.

OBJECTIVE: To assess the association between the fetal sex and preterm birth.

METHODS: We performed a retrospective population-based cohort study using the 1995–1997 registration twin data in the United States (148,234 live-birth twin pairs). The twin pairs were divided into 3 groups: male-male (male-male), female-female, and opposite sex. We used 3 different cutoff values of preterm birth: less than 28, 32, and 36 gestational weeks. The preterm birth rates among the 3 study groups were compared, and the adjusted risk ratios (relative risk) were estimated by multiple logistic regression.

RESULTS: The male-male twin pairs had the highest pre-term birth rate (less than 28 weeks: 4.9%; less than 32 weeks: 12.4%; less than 36 weeks: 40.2%), the female-female twin pairs were intermediate (less than 28 weeks: 4.1%; less than 32 weeks: 10.6%; less than 36 weeks: 37.8%), and the opposite-sex twin pairs had the lowest rate (less than 28 weeks: 4.1%; less than 32 weeks: 10.1%; less than 36 weeks: 36.8%). Adjustment for important confounding factors or excluding twin pairs born to mothers who had an induction of labor or a cesarean delivery with medical complications did not change the results. The adjusted relative risks (95% confidence intervals) were 1.19 (1.11, 1.27), 1.21 (1.16, 1.26), and 1.09 (1.07, 1.11), respectively, for male-male twins compared with the opposite-sex twins under the 3 different cutoff values of preterm births.

CONCLUSION: Male sex is associated with increased risk of preterm births in twin pregnancy.

LEVEL OF EVIDENCE: II-2

This article has been cited by other articles:

				Other articles noted Evid. Based Med., September 1, 2004; 9(5): e5 - e5. [Full Text] [PDF]

				H. Tan, S. W. Wen, M. Walker, K. F. K. Fung, K. Demissie, and G. G. Rhoads The Association Between Fetal Sex and Preterm Birth in Twin Pregnancies Obstet. Gynecol., July 1, 2004; 104(1): 196 - 196. [Full Text] [PDF]

				I. M. Usta and A. H. Nassar The Association Between Fetal Sex and Preterm Birth in Twin Pregnancies Obstet. Gynecol., July 1, 2004; 104(1): 195 - 196. [Full Text] [PDF]