title: Size at birth and adult fat mass in twin sheep are determined in early gestation.
abstract: Size at birth is related to adult health outcomes. Twins are born smaller than singletons; this has been assumed to be secondary to limited nutrient supply in late gestation.We hypothesised that growth trajectory in twins, and the adult consequences of being conceived a twin, are determined in early gestation. Twin pregnancies in sheep were randomised to reduction of one twin on day 42 of a 148 day pregnancy by intra-thoracic KCl (Reductions, n =46) or a sham procedure (Twins, n =22). Singleton-bearing ewes also underwent a sham procedure (n =27). Ewes lambed spontaneously. Linear measures of size at birth were similar in Twins and Reductions, and significantly less than in Singletons. Birthweight was lower in Twins and Reductions than in Singletons, and less in Twins than in Reductions (means (SEM): Singletons, liveborn n =23: 6.59 (0.17) kg; Twins, liveborn n =36: 5.23 (0.16) kg; Reductions, liveborn n =27: 5.76 (0.15) kg; all comparisons P <0.05). Reductions grew most rapidly between birth and weaning (Singletons, 20.0 (0.4) g kg⁻¹ day⁻¹; Twins, 20.0 (0.3) g kg⁻¹ day⁻¹; Reductions, 21.0 (0.3) g kg⁻¹ day⁻¹, P <0.05) and were of similar weight as Singletons by weaning; Twins remained smaller by weaning but grew most rapidly thereafter (Singletons, 1.6 (0.1) g kg⁻¹ day⁻¹; Twins, 2.1 (0.1) g kg⁻¹ day⁻¹; Reductions, 1.6 (0.1) g kg⁻¹ day⁻¹, P <0.01), so that all groups had similar weight at 2 years. However, Twins and Reductions had greater percentage fat mass than Singletons at 2 years (Singletons, 11.1 (1.1)%; Twins, 14.8 (1.2)%; Reductions, 15.5 (1.1)%, P <0.05). Thus, in twins, fetal growth trajectory, linear size at birth and adult fat mass are largely determined in early gestation. If this is also true in humans, there are important implications for interventions aimed at optimising fetal growth and pregnancy outcome.
authors.affiliation: Liggins Institute, University of Auckland and National Research Centre for Growth and Development, Auckland, New Zealand.
authors.forename: S N
authors.initials: SN
authors.lastname: Hancock
authors.forename: M H
authors.initials: MH
authors.lastname: Oliver
authors.forename: C
authors.initials: C
authors.lastname: McLean
authors.forename: A L
authors.initials: AL
authors.lastname: Jaquiery
authors.forename: F H
authors.initials: FH
authors.lastname: Bloomfield
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood; D000273:Adipose Tissue / Q000033:anatomy & histology*; D000818:Animals; D001699:Biometry; D001724:Birth Weight; D001786:Blood Glucose / Q000032:analysis; D004958:Estradiol / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005865:Gestational Age; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008098:Litter Size; D008297:Male; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000097:blood; D012756:Sheep / Q000033:anatomy & histology* / Q000502:physiology
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D020155:3-Hydroxybutyric Acid; D006854:Hydrocortisone