Transient changes in body weight and behavior during the placentation period in non-human primates and rodents

During early pregnancy, many women experience physical changes, including nausea and vomiting of pregnancy (NVP), which negatively impact their quality of life. However, the absence of model animals has limited our understanding of such pregnancy-associated physiological changes. Here, we examined pregnancy-associated metabolic and behavioral changes in common marmosets and mice. Marmosets exhibited a transient weight decrease during the period of placental development in approximately 22% of pregnancies. Some marmosets repeatedly showed transient weight loss across multiple pregnancies, suggesting individual variations in the likelihood of pregnancy-associated weight loss. Although mice did not show apparent alteration in body weight, they exhibited a slowdown in food intake and alterations in locomotor activity during the corresponding phase. The observed transient changes in pregnant marmosets and mice may provide a basis for generating hypotheses regarding physiological changes associated with placentation.