Differential kinetics of serum and cervical insulin-like growth factor-binding protein-1 during mifepristone-misoprostol-induced medical termination of early pregnancy.

The kinetics of cervical and circulating phosphoisoforms of insulin-like growth factor-binding protein-1 (IGFBP-1) in normal and pathological early pregnancy are not well known. We investigated the profiles of IGFBP-1 in serum and in cervical secretion during medical termination of early pregnancy. Sixteen women requesting termination of pregnancy, with <63 days of amenorrhoea, received 200 mg of mifepristone on day 0, followed by either oral or vaginal administration of 0.8 mg of misoprostol on day 2. Serum and cervical swab samples, collected up to 6 weeks following the beginning of the treatment, were analysed for IGFBP-1 using two immunoenzymometric assays recognizing different patterns of IGFBP-1 phosphoisoforms. Serum mifepristone was also assayed. In the cervical samples, IGFBP-1 concentration, measured with both assays, increased substantially 2 days following administration of mifepristone. At 3 h after administration of misoprostol, IGFBP-1 had further increased several-fold in the cervix, but the increase was more pronounced as measured by the assay with preference for the amniotic fluid isoforms of IGFBP-1. A strong negative correlation was found between the time to abortion and the increase in cervical IGFBP-1 after administration of misoprostol, as measured by the assay preferring the phosphorylated isoforms of IGFBP-1. At 6 weeks, IGFBP-1 in the cervix had decreased to lower than pre-treatment levels, as measured by both assays. In serum, both assays showed a significant increase in IGFBP-1 concentrations after administration of mifepristone, and the highest values were measured on day 2, already before misoprostol administration. Thus, the kinetics of circulating and cervical IGFBP-1 differed from each other, indicating different sources and regulation of serum and cervical IGFBP-1.