What Are the Signs of Pregnancy for Female Rats?

A female rat's pregnancy lasts between 21 and 23 days. Rats reach sexual maturity as early as five weeks of age and quickly develop regular fertility schedules, which makes breeding rats a predictable process. A rat may get pregnant through a single sexual encounter, though most rats require multiple mating sessions before pregnancy actually occurs. Feed pregnant rats a nutritious diet and allow them to get regular exercise.

  1. Weight Gain

    • A rat may gain weight during her entire pregnancy, or the weight gain may occur close to the birth. The pregnant rat's belly will protrude and her body will become pear-shaped. Walking will become uncomfortable and you may even be able to see the babies kicking through her belly.

    Protruding Nipples

    • A few days into pregnancy, the hair around a rat's nipples will begin to diminish and her nipples will protrude. The nipples may appear to be swollen and change color slightly.

    Aggressive Behavior

    • Pregnant rats experience a surge of hormones that sometimes cause aggressive behavior. A pregnant rat may become anxious when touched or if another rat gets too close and she may bite or squeal.

    Social Regression

    • A pregnant female rat may begin to avoid other rats or their owners and appear to regress socially. She may become anxious when confronted by other rats and prefer to be alone.

    Mucous Plug

    • A white-colored mucous plug forms on the vagina of the female rat after she becomes pregnant. This plug is designed to protect the uterus by blocking the cervix and it will discharge before the birthing process begins.