LH concentrations in human maternal and cord serum.

Maternal blood and umbilical cord venous blood were collected immediately after delivery in 32 subjects who had completed normal birth during the 38 to 41 weeks of pregnancy, and the concentrations of human chorionic gonadotropin (hCG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were determined by radioimmunoassay (RIA). The specific LH RIA utilized for the measurement of LH is unaffected by hCG at sample levels as high as 500 IU/ml. HCG concentrations were 10,370 +/- 1,480 mIU/ml (mean +/- SE) in mother's serum and 34.5 +/- 5.2 ml in cord serum, while LH concentrations were 0.729 +/- 0.055 and 0.438 +/- 0.033 ng/ml, respectively. The concentration of all 3 gonadotropins in maternal serum was greater than cord serum and the ratio was markedly high with 302:1 for hCG, while the ratio was smaller for LH, being 1.7:1, while that for FSH was 4.2:1. There was no difference in the levels of LH and FSH in relation to the sex of the fetus.