Comparison of plasma steroid and gonadotrophin profiles in spontaneous cycles in which conception did and did not occur

Luteinizing hormone (LH), follicle stimulating hormone (FSH), oestradiol and progesterone were measured in plasma from blood samples obtained daily throughout 23 menstrual cycles in a total of 18 normal women. Eight of these women were trying to conceive at the time of investigation and five succeeded. The subjects were divided into those who were not exposed to pregnancy (Group I), those who became pregnant (Group II) and those who were trying to become pregnant but failed to do so (Group III). The mean profiles of each of the four hormones were similar for the three groups studied. Statistical comparisons (using 't' tests) between Groups II and III showed that FSH concentrations were significantly lower (P less than 0.01) in the late follicular phase (Days -7 to -3 before the LH peak) in Group III. Similarly, progresterone concentrations were significantly lower (P less than 0.05) during the early luteal phase (Days +3 to +7 after the LH peak) in Group III.