At what gestation is labor induction recommended for well-controlled pregnancy-induced hypertension (PIH)?

From the Guidelines

Induction of labor is recommended for women with well-controlled pregnancy-induced hypertension (PIH) at 37 weeks' gestation. This recommendation is based on the most recent and highest quality study, which suggests that induction of labor is associated with improved maternal outcome and should be advised for women with gestational hypertension or mild pre-eclampsia at 37 weeks' gestation 1. The optimal timing of delivery depends on fetal wellbeing, gestational age, and type of hypertensive disorder.

Key Considerations

• The specific timing of induction may vary depending on the severity of hypertension and presence of other complications.
• Women with well-controlled gestational hypertension without severe features may be induced at a later gestational age, but 37 weeks is the recommended threshold for those with mild pre-eclampsia.
• Prior to induction, patients should have their blood pressure well-controlled, typically with medications such as labetalol, nifedipine, or methyldopa, as outlined in the European Heart Journal position paper 1.
• Continuous maternal and fetal monitoring is essential during labor, and magnesium sulfate prophylaxis should be considered for seizure prevention in preeclamptic patients.

Rationale

The recommendation to induce labor at 37 weeks' gestation is based on the balance between the risks of continuing the pregnancy and the risks of prematurity. Continuing the pregnancy beyond 37 weeks may increase the risk of progression to severe preeclampsia, placental abruption, and fetal growth restriction, while early delivery is the definitive treatment for PIH, as the condition resolves after removal of the placenta. The study published in the European Heart Journal 1 provides the most recent and highest quality evidence to support this recommendation.

From the Research

Gestation and Labor Induction for PIH

• The optimal timing of birth for women with chronic or gestational hypertension at term is a topic of ongoing research 2.
• A study published in 2024 found that planned birth at 38+0-3 weeks (versus usual care) resulted in birth an average of 6 days earlier, and no differences in poor maternal outcome or neonatal morbidity 2.
• The study suggests that planned birth at 38+0-3 weeks may be a clinical option for women with well-controlled pregnancy-induced hypertension (PIH) 2.
• Another study published in 2017 found that compliance with clinical practice guidelines for management of hypertension during pregnancy has potential to translate to significant maternal and perinatal health benefits 3.
• The American College of Obstetricians and Gynecologists (ACOG) recommends that women with gestational hypertension or preeclampsia at or beyond 37 weeks of gestation should be considered for delivery, regardless of fetal lung maturity 2, 4.

Key Findings

• Women with chronic or gestational hypertension who reach term and remain well may benefit from planned birth at 38+0-3 weeks 2.
• The selection of the antihypertensive drug and its route of administration depend on the expected time of delivery 4.
• Methyldopa, labetalol, and calcium antagonists are the drugs of choice for treating hypertension in pregnancy 5, 4, 6.
• Women with a history of hypertensive disorders in pregnancy, particularly those with pre-eclampsia, are at high risk of developing cardiovascular disease later in life 4.

Recommendations

• The current European guidelines recommend initiating drug treatment in pregnant women with persistent elevation of blood pressure ≥ 150/95 mmHg and at values > 140/90 mmHg in women with gestational hypertension (with or without proteinuria) 5, 4.
• Labor induction is recommended for women with well-controlled PIH at or beyond 37 weeks of gestation, but the optimal timing of birth is still a topic of debate 2, 3.