Serum levels of pregnancy-specific beta 1-glycoprotein (SP1) and human chorionic gonadotropin (beta-hCG) in women using an intrauterine device.

Forty-two women using intrauterine contraceptive devices volunteered in a study in which blood samples were drawn in late luteal phase 1-3 times during 73 menstrual cycles. In all 129 blood samples were collected. Pregnancy-specific beta 1-glycoprotein (SP1) and human chorionic gonadotropin (beta-hC) were measured by radioimmunoassays. SP1 was measurable in 5/129 samples and beta-hCG in 2/123 samples. Both SP1 and beta-hCG were measurable in 2 samples. All women in the study had regular menstrual periods. It is concluded that an early implantation and subsequent abortion in connection with a "normal" menstruation could occur but in a frequency that is much lower than in women using no contraception.