Serum concentrations of oestradiol-17beta, progesterone, relaxin and chorionic gonadotrophin during blastocyst implantation in natural pregnancy cycle and in embryo transfer cycle in the rhesus monkey

The present study was undertaken to assess the temporal association betweenthe profiles of serum concentrations of oestradiol-17beta, progesterone,chorionic gonadotrophin (CG) and relaxin in pregnancies establishednaturally, and after embryo transfer, as well as in failed pregnancies inrhesus monkeys. In naturally mated cycles (group 1) a conception rate of75% was obtained. In group 1, the mean day of CG detection in serum was11.5 +/- 1.9 day post-ovulation, and for relaxin, 9.0 +/- 2.5 daypost-ovulation. In group 2, embryo transfer to synchronous, non-matedsurrogate recipients was performed; seven embryo transfer cycles yieldedthree pregnancies which were allowed to continue to term and normal infantswere delivered. In embryo transfer cycles the mean day of CG detection was14.8 +/- 1.8 day post- ovulation, and for relaxin, 11.4 +/- 2.6 daypost-ovulation. A delay of about 3 days was observed in the appearance incirculation of CG (P < 0.05) and also of relaxin (P < 0.05) betweennatural mated and embryo transfer conception cycles. Significantdifferences (P < 0.05 for progesterone and P < 0.03 for oestradiol)were obtained for the areas under the curves for progesterone andoestradiol between days 12 and 16 in conception cycles compared with failedpregnancies. These data provide the first observation of the normalhormonal signals associated with maternal recognition of transferredembryos during the peri- implantation period, and suggest that the use ofsuch an experimental primate embryo transfer model may help to elucidatecomponents of maternal and embryonic signal-response mechanisms duringembryo implantation.