Birth size and gestational age in opposite-sex twins as compared to same-sex twins: An individual-based pooled analysis of 21 cohorts

Aline Jelenkovic, Reijo Sund, Yoshie Yokoyama, Yoon Mi Hur, Vilhelmina Ullemar, Catarina Almqvist, Patrik Ke Magnusson, Gonneke Willemsen, Meike Bartels, Catharina Em Van Beijsterveldt, Leonie H. Bogl, Kirsi H. Pietiläinen, Eero Vuoksimaa, Fuling Ji, Feng Ning, Zengchang Pang, Tracy L. Nelson, Keith E. Whitfield, Esther Rebato, Clare H. LlewellynAbigail Fisher, Gombojav Bayasgalan, Danshiitsoodol Narandalai, Morten Bjerregaard-Andersen, Henning Beck-Nielsen, Morten Sodemann, Adam D. Tarnoki, David L. Tarnoki, Syuichi Ooki, Maria A. Stazi, Corrado Fagnani, Sonia Brescianini, Lise Dubois, Michel Boivin, Mara Brendgen, Ginette Dionne, Frank Vitaro, Tessa L. Cutler, John L. Hopper, Robert F. Krueger, Matt McGue, Shandell Pahlen, Jeffrey M. Craig, Richard Saffery, Claire Ma Haworth, Robert Plomin, Ariel Knafo-Noam, David Mankuta, Lior Abramson, S. Alexandra Burt, Kelly L. Klump, Robert F. Vlietinck, Catherine A. Derom, Ruth Jf Loos, Dorret I. Boomsma, Thorkild I.A. Sørensen, Jaakko Kaprio, Karri Silventoinen

Research output: Contribution to journalArticlepeer-review

Abstract

It is well established that boys are born heavier and longer than girls, but it remains unclear whether birth size in twins is affected by the sex of their co-twin. We conducted an individual-based pooled analysis of 21 twin cohorts in 15 countries derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), including 67,850 dizygotic twin individuals. Linear regression analyses showed that boys having a co-twin sister were, on average, 31 g (95% CI 18 to 45) heavier and 0.16 cm (95% CI 0.045 to 0.274) longer than those with a co-twin brother. In girls, birth size was not associated (5 g birth weight; 95% CI -8 to -18 and -0.089 cm birth length; 95% CI -0.202 to 0.025) with the sex of the co-twin. Gestational age was slightly shorter in boy-boy pairs than in boy-girl and girl-girl pairs. When birth size was standardized by gestational age, the magnitude of the associations was attenuated in boys, particularly for birth weight. In conclusion, boys with a co-twin sister are heavier and longer at birth than those with a co-twin brother. However, these differences are modest and partly explained by a longer gestation in the presence of a co-twin sister.

Original languageEnglish
Article number6300
JournalScientific Reports
Volume8
Issue number1
DOIs
StatePublished - 1 Dec 2018

All Science Journal Classification (ASJC) codes

  • General

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