PREIMPLANTATION HORMONAL DIFFERENCES BETWEEN THE CONCEPTION AND NON-CONCEPTION MENSTRUAL CYCLES OF 32 NORMAL WOMEN

We compared daily urinary concentrations of oestrogen and progesterone metabolites in paired menstrual cycles (conception and non-conception ) from 32 women, Volunteers with no known fertility problems were enro lled in the study at the time they began trying to become pregnant, Th ey collected first-morning urine specimens and kept daily records of m enstrual bleeding and sexual intercourse for 6 months or until they be came clinically pregnant. Intercourse in non-conception cycles was clo se to the time of ovulation so that failure to conceive was caused by factors other than poorly timed intercourse. Compared with non-concept ion cycles, conception cycles had a steeper early luteal rise in proge sterone and higher mid-luteal oestrogen and progesterone concentration s. These hormonal characteristics may be markers of better quality cyc les, but because all these differences were in the luteal phase, we ca nnot rule out the possibility that the preimplantation embryo had stim ulated early increases in steroid production. We propose an analysis s trategy that could help support or refute the importance of preimplant ation embryonic signalling, but our small sample size limits our own c onclusions about this mechanism.