Body weight changes throughout pregnancy in the common marmoset Callithrix jacchus.

Adult female common marmosets were weighed weekly for periods of 6-30 months. Of 27 animals, 25 were pregnant at some stage of the investigation. Patterns of body weight change throughout singleton, twin and triplet pregnancies were obtained and compared. Maternal weight increase was dependent on the number of young in utero; however, little or no change in weight was observed during the first 13 weeks of gestation, irrespective of the number of offspring delivered subsequently. The overall maternal:fetal body weight ratio was 1.00:0.21, ranging from 1.00:0.11 for singleton to 1.00:0.26 for triplet pregnancies. Lactation had little or no effect on maternal body weight during the first 4 weeks postpartum.