Placental morphometry in hypertensive disorders of pregnancy and its relationship with birth weight in a Latin American population

Objective: To assess the placental morphometry in pregnancies with hypertensive disorders of pregnancy (HDP) and its relationship with birth weight (BW). Study design: Cohort study of placental morphometry and fetal outcomes of 954 pregnancies at a university hospital in Ribeirao Preto, Sao Paulo, Brazil, in 2010. HDP categories were: chronic (CH), gestational (GH), preeclampsia (PRE) and pre-eclampsia superimposed on chronic hypertension (CH + PRE). Associations between BW and placental measures (PM) in pregnancies were evaluated by multiple linear regression analyses. Main outcome measures (PM): Placental weight (PW, g), largest and smallest diameters (cm), thickness (cm), eccentricity, area (cm(2)), volume (cm(3)), BW/PW ratio and PW/BW ratio (efficiency). Results: The frequencies of each HDP categories were 6.5% CH; 7.6% GH; 6.1% PRE, and 2.0% CH + PRE. PW, largest and smallest diameters, area and BW/PW ratio were statistically different between HDP and the normotensive group, with the lowest values for CH + PRE; the remaining measures showed no difference. BW was lower in HDP than in the normotensive group (p = 0.016). BW and PW were highly correlated in the presence of HDP (r = 0.79, p < 0.001). Sixty-seven percent of BW variability was accounted for PM (p < 0.001), and increased to 81% when maternal variables, gestational age and sex were added (p < 0.001). Conclusions: Hypertensive disorders of pregnancy significantly influence the growth of both the placenta and the fetus. PM explain 67% of BW variability, and CH + PRE was the category with the strongest association to the results.