Relationship between ovarian and placental steroid production during early pregnancy in the marmoset monkey (Callithrix jacchus).

Concentrations of progesterone, 17 alpha-hydroxyprogesterone, oestrone and oestradiol-17 beta in peripheral and utero-ovarian vein blood were measured during the first 60 days of pregnancy. The same hormones were also measured in peripheral blood samples from non-fertile cycles. Peripheral levels of 17 alpha-hydroxyprogesterone, oestrone and oestradiol increased gradually during early pregnancy whereas concentrations of progesterone declined. The patterns of secretion of progesterone, 17 alpha-hydroxyprogesterone and oestrone, but not oestradiol, were significantly different in fertile and non-fertile cycles by 15 days after ovulation. Comparison of hormone values in peripheral and utero-ovarian vein samples from ovaries with and without corpora lutea (Days 7, 9, 13, 21, 40 and 60 of pregnancy) showed that: (a) progesterone was secreted by the corpus luteum until at least Day 40 by which time there was also placental secretion; (2) although 17 alpha-hydroxyprogesterone was secreted by the corpus luteum, the relative contribution of luteal and placental secretion after Day 21 was not clear; (3) oestrone secretion by the corpus luteum was no longer detectable by Day 40, but placental oestrone secretion appeared to be present by this time; (4) the corpus luteum did not secrete significant amounts of oestradiol at any stage of early pregnancy, although there was evidence for placental secretion by Day 40. These results suggest that progesterone secretion by the corpus luteum of early pregnancy continues beyond the time when oestrogen secretion has declined. The corpus luteum to placental shift in the marmoset appears to occur at a later stage of pregnancy than it does in the macaque monkey and probably also in man.