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How the Saint Louis Zoo found out a chimpanzee was pregnant

The zoo shared how it found out Utamu was pregnant and gave some information about chimpanzee reproductive cycles

ST. LOUIS — A chimpanzee at the Saint Louis Zoo is pregnant and due to give birth this fall at Jungle of the Apes.

The zoo announced 18-year-old Utamu’s pregnancy last month and is continuing to give updates on her pregnancy on social media.

On Wednesday, the zoo shared how its staff found out Utamu was pregnant and gave some information about chimpanzee reproductive cycles.

The zoo said chimpanzees have about a 36-day reproductive cycle. The zoo’s primate care team tracks cycles for all the female chimps as part of their daily husbandry monitoring.

When a female is ovulating – when she can become pregnant – she develops an estrus swelling. This means her behind swells up and looks like a small inflated pink balloon. For the rest of her cycle, the area is deflated and has loose pink skin.

Female chimps also menstruate during their cycle. So, if one of those events is missing or late, it can often be the first indication of a potential pregnancy, the zoo said.

RELATED: Saint Louis Zoo chimpanzee to give birth this fall

How does the zoo confirm a pregnancy?

The zoo uses an at home pregnancy test – the exact same type of test that humans use to confirm a pregnancy. The zoo said Utamu is trained to urinate when asked so staff can collect it and apply it to a pregnancy test.

The zoo also uses a secondary method to confirm a pregnancy.

The zoo has its own endocrinologist, Corinne Kozlowski, and an endocrinology laboratory. One way to have a secondary verification of a chimp pregnancy is to compare progesterone levels of a suspected pregnant chimp to progesterone levels of a non-pregnant chimp.

This can be used to verify pregnancy because progesterone levels rise during pregnancy.

The care team can submit fecal samples from the chimps collected during daily cleaning to the lab where Dr. Kozlowski can evaluate them, the zoo said.

You can follow “Utamu: Path to Motherhood” on the zoo’s website, Facebook, Instagram and Twitter pages for updates on her pregnancy.