In a cross-sectional study, the serum levels of pregnancy-specific beta 1-glycoprotein (PSBG), hCG, human LH, and progesterone were measured by RIAs during 94 mid or late luteal phases of 69 women using oral contraceptives. Subsequent spontaneous menstruation took place in every cycle. None of the women using oral contraceptives had any PSBG or hCG-like immunoreactivity in serum. In women with intrauterine devices, PSBG was found in six cycles (6.4%) and hCG-like immunoreactivity was demonstrated in one cycle only, where PSBG also was present. In two out of six PSBG-positive cycles, menstruation was delayed by 5 and 16 days. Although rare, the transient occurrence of trophoblastic antigens in women using intrauterine contraception is taken as evidence for an occult pregnancy in these apparently infertile cycles.
PIP: Serum levels of pregnancy-specific beta-1-glycoprotein (PSBG), human chorionic gonadotropin (hCG), human luteinizing hormone (LH), and progesterone were measured by radioimmunoassays during 94 mid- or late luteal phases of 69 women using IUDs and 34 women using oral contraceptives (OCs) in a cross-sectional study. hCG-like immunoreactivity was found in 1 of 94 cycles (1.1%) of women using IUD contraception, and in none of those taking OCs. The positive hCG reaction was found on Day 27 of the cycle. In the hCG-positive sample, hCG concentration was 19 mIU/ml. Cross-reaction by LH was unlikely since the LH concentration was 82 ng/ml, well below the cross-reacting level of the assay. PSBG was found in 6 of 94 cycles (6.4%) of IUD users, and in none of OC users. Levels varied from 11-21 ng/ml, and PSBG was found on Days 24-27 of the cycle. 1 cycle demonstrated both hCG and PSBG, and the PSBG concentration was 15 ng/ml. In trophoblastic antigen-positive IUD cycles, menstruation was delayed from the expected date by 3 or more days in 2 cases. In the case where both markers were found, menstruation was delayed by 16 days. Aside from menstrual delay in 2 subjects, no typical changes were noted in the bleeding pattern of those cycles where trophoblast-specific antigens were detected. Although rare, the transient occurrence of trophoblastic antigens in women using IUDs was taken as evidence for occult pregnancy in these apparently infertile cycles.