Preliminary results on plasma progesterone levels during pregnancy and superfetation in the hare, Lepus Europaeus.

Peripheral plasma progesterone levels were studied in pregnant hares. A rise occurred at the beginning of pregnancy, followed by a plateau from Days 10 to 35, and then a drop during the days just before parturition. No significant differences were noted between progesterone levels in pregnancies initiated at the pre-partum oestrus and those from other oestrous periods.