Endocrine Changes in Full-Term Pregnancies and Pregnancy Loss Due to Energy Restriction in the Common Marmoset (Callithrix jacchus)

Common marmosets, a New World primate, respond to a modest energy restriction with early termination of the pregnancy. Within female marmosets, comparisons (n = 6) between a normal, term pregnancy and a restriction-induced aborted pregnancy were used to establish cortisol, free estradiol, and chorionic gonadotropin (CG) as urinary markers of placental and fetal function under these two conditions. Abortions occurred 11-47 d after a 25% energy reduction during midpregnancy for all females. Cortisol concentrations were significantly lower in the last 2 wk for the restricted pregnancy than for matched samples in the normal term pregnancy. Both estradiol and estrone were examined in free and conjugated forms. Only free estradiol showed a significant reduction in mean concentrations during midpregnancy for the restricted females compared with their normal, term pregnancies. Mean CG levels from each female served as an independent marker of placental differentiation and function. CG levels were significantly lower during the 2 wk before abortion compared with matched days from a normal, term pregnancy. These data provide evidence that estradiol and cortisol are useful markers of placental and fetal viability in the common marmoset, and their reduced concentration following energy restriction suggests that restriction is not acting as a classical stressor by increasing cortisol and, subsequently, estradiol concentration.