Insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 (IGFBP-2) were measured in amniotic fluid, extraembryonic fluid and maternal serum from 20 women with apparently normal first trimester pregnancies prior to termination. A further 111 specimens of amniotic fluid were collected from women at 10-20 weeks of pregnancy. Levels of IGFBP-2 were similar in coelomic fluid and maternal serum. Levels in amniotic fluid were lower than those in serum and coelomic fluid (Mann-Whitney test; P = 0.0002 and P < 0.0001 respectively). The levels of IGF-II were much higher in maternal serum than in coelomic fluid, and higher in the latter than in amniotic fluid (Mann-Whitney test; P < 0.0001 for both situations). The levels of IGFBP-2 were relatively low at 10-11 weeks (medians 19.8 and 61.1 micrograms/l) but thereafter increased to 20 weeks (median 1400 micrograms/l). The levels of IGF-II showed a similar pattern. The findings suggest that the role of IGF-II and IGFBP-2 in the regulation of growth or differentiation of the fetus or of its surrounding membranes may change with advancing pregnancy.