Inclusion and exclusion criteria
The inclusion criteria for this study were singleton pregnancies resulting in the live birth or stillbirth of phenotypically normal babies at > 24 weeks’ gestation. Pregnancies with fetal aneuploidies or major defects diagnosed in the antenatal or neonatal period and pregnancies ending in miscarriage at <24 week’s gestation were excluded.
For every 5 cases with CH, we selected approximately 1 control from uncomplicated pregnancies that resulted in the live birth of phenotypically normal neonates that were matched to the cases for storage time of maternal serum and racial origin, because the incidence of chronic hypertension is 3 times higher in Black than white women.