Mating in the rhesus monkey (Macaca mulatta) after conception and its relationship to oestradiol and progesterone levels throughout pregnancy

Abstract

Behavioral and hormonal data were collected throughout pregnancy in captive rhesus monkeys. Heterosexual pairs observed in daily time-limited mating tests showed 2 distinct periods of increased sexual interaction, as measured by the incidence of ejaculation. One period was coincident with the preovulatory estradiol peak, while the other occurred between the 6-10th wk of pregnancy. The positive relationship found during the menstrual cycle between the ratio of circulating estradiol:progesterone and degree of sexual activity continued for the first 8 wk of pregnancy. Sexual activity ceased in the 2nd half of pregnancy despite a continued high estradiol:progesterone ratio.