LEVELS OF INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-I INCREASE RAPIDLY IN AMNIOTIC-FLUID FROM 11 TO 16 WEEKS OF PREGNANCY

Concentrations of IGF-binding protein-1 (IGFBP-1) were measured by rad ioimmunassay in 176 amniotic fluid samples from 9 to 20 and 36 to 42 w eeks of pregnancy. Low levels of IGFBP-1 were present at 9 and 10 week s (median values 35.0 and 45.0 mug/l respectively). After 10 weeks, th e levels increased by four orders of magnitude to reach a peak at 16 w eeks (median 145.2 mg/l). After 16 weeks levels fell. Near term, the l evels (median 27.1 mg/l) were lower than in the second trimester. The rapid increase in IGFBP-1 shown by radioimmunoassay was confirmed by W estern ligand blotting. The findings suggest that the regulatory role of IGFBP-1 in the growth or differentiation of the fetus or of its sur rounding membranes may change as pregnancy advances.