Urinary sex steroid hormone and placental leucine aminopeptidase concentration differences between live births and stillbirth of Bornean orangutans (Pongo pygmaeus)

Background Under the environment of pregnancy, the placenta assumes an important steroidogenic role in the maintenance of pregnancy. Methods Urinary placental leucine aminopeptidase (PLAP), estrone‐3‐glucuronide (E1G), and pregnanediol‐3‐glucuronide (PdG) concentrations were compared among five pregnancies (four live births and one stillbirth) in four orangutans. Results The gestation period of the stillbirth (223 days) was shorter than that of the live births (239‐254 days). In females who gave a live birth, average PLAP and E1G concentrations increased until the delivery. Conversely, in the female who gave a stillbirth, PLAP concentration failed to increase, and E1G concentration was significantly low in late pregnancy period. Regarding PdG concentrations, there was no significant difference among all pregnancies. Conclusions This is the first study reporting a change in urinary PLAP, E1G, and PdG concentrations during orangutan stillbirth and live birth pregnancies. The findings will assist in developing pregnancy screening tests.