Abstract
We have measured L/S ratios, together with the concentrations of F and DS of 414 amniotic fluid specimens obtained from 13 to 44 weeks gestation. We found that the L/S ratios begin to increase after 33 weeks gestation, from mean values of 0.7 ± 0.2 (± SE) at 33 weeks to 1.8 ± 0.3 at 34 weeks and 3.5 ± 0.7 at 35 weeks. There are no significant differences in concentrations of amniotic fluid F from 31-32 weeks up to 35 weeks. F concentrations rise thereafter from 51 ± 6.3 ng/ml at 35 weeks to 63 ± 4.5 ng/ml at 36 weeks and 67.5 ± 6.3 ng/ml at 37 weeks. DS concentrations in amniotic fluid rise slowly from 31-32 weeks (80 ± 13 ng/ml) to the 35th week 110 ± 7.8 ng/ml) and this rise continues to term. While others have shown that the L/S ratios in amniotic fluid correlate well with fetal lung maturation, this does not appear to be the case with cortisol, since cortisol concentrations increase following the increases of L/S ratios. However, DS concentrations in amniotic fluid do begin to increase before the rise in the L/S ratio, likely reflecting increased availability of fetal placental estrogen precursor. Augmented estrogen production could serve a role in increasing fetal lung surfactant synthesis, perhaps by leading to increased fetal pituitary prolactin secretion.
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Milewich, L., Johnston, J., Bradfield, D. et al. 201 THE RELATIONSHIP OF AMNIOTIC FLUID DEHYDROISOANDROSTERONE SULFATE (DS) AND CORTISOL (F) CONCENTRATIONS WITH LECITHIN TO SPHINGOMYELIN (L/S) RATIOS DURING HUMAN CESTATION. Pediatr Res 12 (Suppl 4), 397 (1978). https://doi.org/10.1203/00006450-197804001-00206
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DOI: https://doi.org/10.1203/00006450-197804001-00206