Amniotic fluid cortisol and alpha-fetoprotein in normal and aneuploid pregnancies

Cortisol and alpha-fetoprotein (AFP) levels were measured in amniotic fluid (AF) samples at 15-20 weeks of gestation from 125 normal pregnancies and 29 pregnancies affected by aneuploidy. The normal pregnancy group was further subdivided into 'low' AF-AFP (less than 0.6 MOM, n = 60) and 'normal' AF-AFP (0.6 less than AFP less than 1.4 MOM, n = 65). A significant, inverse, linear correlation was found between cortisol and AF-AFP for both normal AFP and low AFP groups (r = -0.26, and r = -0.4, respectively, p less than 0.05). Gestational age was significantly correlated with both cortisol and AFP levels in the normal pregnancy groups. No difference was found when cortisol levels were compared between the low and normal AFP groups. The correlation between cortisol and AFP in aneuploid pregnancies was not significant (p = 0.37). The strong association between cortisol or AFP and gestational age in normal pregnancy (p less than 0.00001) was lost in trisomic gestation. We conclude that higher cortisol levels do not seem to be the cause of low AFP in normal or aneuploid pregnancies.