Chronic hypertension and adverse pregnancy outcome: a cohort study

Objective: To examine the association between chronic hypertension (CH) and a wide range of adverse pregnancy outcomes after adjustment for confounding factors in obstetric history and maternal characteristics.

Methods: This was a prospective screening study for adverse pregnancy outcomes in women with singleton pregnancies attending the first routine hospital visit at 11+0-13+6
weeks’ gestation. Data on maternal characteristics, medical and obstetric history and pregnancy outcomes were collected. Regression analysis was performed to examine the association between CH and adverse pregnancy outcomes including late miscarriage, stillbirth, pre-eclampsia (PE), gestational diabetes mellitus (GDM), spontaneous and iatrogenic preterm birth (PTB), small for gestational age (SGA) neonate, large for gestational age (LGA) neonate and elective and emergency cesarean section (CS).

Results: The study population of 109,932 pregnancies included 1,417 (1.3%) with CH. After adjusting for potential confounding variables from maternal characteristics, medical
and obstetric history, CH was associated with increased risk of stillbirth OR 2.38, 95% CI 1.51-3.75), PE (OR 5.76, 95% CI 4.93-6.73), SGA (OR 2.06, 95% CI 1.79-2.39), GDM (OR 1.61, 95% CI 1.27-2.05), iatrogenic PTB <37 weeks (OR 3.73, 95% CI (3.07-4.53) and elective CS (OR 1.79, 95%CI 1.52-2.11), decreased risk of LGA (OR 0.65, 0.51-0.83), and had no significant effect on late miscarriage, spontaneous PTB or emergency CS.

Conclusion: CH should be combined with other maternal characteristics and medical and obstetric history when calculating an individualised adjusted risk for adverse pregnancy complications. CH increases the risk for stillbirth, PE, SGA, GDM, iatrogenic PTB and elective CS and reduces the risk for LGA.

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