Studies on amniotic prolactin: chromatographic pattern and correlation with the lecithin content.

We have measured the concentrations of prolactin and lecithin in the amniotic fluid from 20 normal pregnant women in the 2nd and 3rd trimester. Prolactin is present totally as a low-molecular-weight form, 'little' prolactin, and appears to correlate negatively with lecithin during the 2nd and positively during the 3rd trimester. On the basis of these results and of the information that prolactin is present as high-molecular-weight isohormones in maternal blood, it is argued that amniotic prolactin is synthesized 'in situ' and that different mechanisms are involved in the regulation of prolactin production.