Patterns of prenatal survival in the common marmoset (Callithrix jacchus).

Fifty common marmoset pregnancies were monitored using ultrasound. The objective was to ascertain if fetal mortality was related to litter size. Prior to analysis we determined abortion rate and litter size were not influenced by repeated ultrasound. Mortality was unrelated to litter size and occurred fairly late in gestation. All singletons born in this study began gestation as twins. It is hypothesized that marmosets may be able to adjust litter size late in pregnancy in response to proximate environmental factors.