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Twin conception reduces birth weight and gestation length in sheep, regardless of fetal number in late gestation

Digby, S.N.ORCID: 0000-0002-4115-4642, Oliver, M.H. and Bloomfield, F.H. (2009) Twin conception reduces birth weight and gestation length in sheep, regardless of fetal number in late gestation. Journal of Developmental Origins of Health and Disease, 1 (Supp. 1). S8.

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Objective: Twins are commonly born both early and small and these factors are associated with adverse long-term health outcomes. The dogma is that constraints of uterine size and placental supply in late gestation are responsible, but there are no data to support this. The periconceptional period is known to be important for fetal development and gestation length. We hypothesised that conception per se as a twin would alter fetal growth and the timing of birth.

Methods: Time-mated twin-bearing ewes were randomly assigned to fetal reduction of one twin (reductions; n532) or a sham procedure (twins; n520). Singleton-bearing ewes (singles; n523) also underwent a sham procedure. Fetal reduction was achieved through ultrasound-guided transabdominal injection of 1.5mL 2M KCl into the heart or chest cavity on day 42 of gestation (term5147 d). Gestation lengths, birth weight, and other anthropometric measurements were recorded at, or shortly after, birth. Data were compared by ANOVA with post-hoc correction and are presented as mean (SEM).

Results: Gestation length was shorter in twins than singles (147.0 (0.32) vs 148.3 (0.34) d; P,0.05); reductions had intermediate gestation length (147.3 (0.46) d). Birth weight was greatest in singles, intermediate in reductions, and least in twins, each group being statistically different (singles 6.60 (0.16) Kg; reductions 5.82 (0.14) Kg; twins (5.23 (0.12) Kg; all comparisons P,0.0001). Other anthropometric data were similar between reductions and twins, with singles significantly larger than these two groups (P,0.05). These findings are not altered by adjustment for gestation length.

Conclusion: Following reduction of twin pregnancies to singletons in early gestation, birthweight and gestation length remain less than in singletons. These are the first experimental data demonstrating that gestation length and birthweight in twin fetuses are determined, at least in part, in early gestation. However, the significantly greater birthweight in reductions compared with twins indicates that there is additional constraint of growth in late gestation. Birth weight and gestation length are therefore influenced by fetal number both at the time of conception and in late gestation. Further studies will determine whether this altered growth has longterm implications for growth and risk of disease.

Item Type: Journal Article
Publisher: Cambridge University Press
Copyright: © 2009 Cambridge University Press
Other Information: oral presentation given @ 6th World Congress on Developmental Origins of Health and Disease. Santiago, Chile. 19 - 22 November
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