1. Birth size and gestational age in opposite-sex twins as compared to same-sex twins: An individual-based pooled analysis of 21 cohorts.
- Author
-
Jelenkovic A, Sund R, Yokoyama Y, Hur YM, Ullemar V, Almqvist C, Magnusson PK, Willemsen G, Bartels M, Beijsterveldt CEV, Bogl LH, Pietiläinen KH, Vuoksimaa E, Ji F, Ning F, Pang Z, Nelson TL, Whitfield KE, Rebato E, Llewellyn CH, Fisher A, Bayasgalan G, Narandalai D, Bjerregaard-Andersen M, Beck-Nielsen H, Sodemann M, Tarnoki AD, Tarnoki DL, Ooki S, Stazi MA, Fagnani C, Brescianini S, Dubois L, Boivin M, Brendgen M, Dionne G, Vitaro F, Cutler TL, Hopper JL, Krueger RF, McGue M, Pahlen S, Craig JM, Saffery R, Haworth CM, Plomin R, Knafo-Noam A, Mankuta D, Abramson L, Burt SA, Klump KL, Vlietinck RF, Derom CA, Loos RJ, Boomsma DI, Sørensen TIA, Kaprio J, and Silventoinen K
- Subjects
- Cohort Studies, Female, Humans, Male, Birth Weight, Body Height, Gestational Age, Twins, Dizygotic
- 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.
- Published
- 2018
- Full Text
- View/download PDF