A Balancing Act: Ideal Delivery Timing & Chronic Hypertension

By Eva Martin, MD of Elm Tree Medical, Inc.

Delivery, like all things in life, is a balancing act, especially in the case of pregnancies with complications. Depending on the complication, be it high blood pressure or diabetes, scheduled delivery earlier than labor starts naturally can be in everyone's best interest- if the risks & benefits balance. In the case of chronic hypertension, timing of delivery must balance the risks to the infant of being born too early with the risk of stillbirth as pregnancy continues. ACOG recommendations for timing of delivery for pregnancies complicated by chronic hypertension are broad (anywhere from 36 to 39 weeks), so a new study examined the risks and benefits of delivery at each week of gestation. 

Chronic hypertension is increasingly common amongst pregnancies in the United States, complicating up to 5% of all pregnancies. Chronic hypertension is defined as (1) an existing diagnosis of hypertension prior to pregnancy, or (2) use of blood pressure medications before pregnancy, or (3) blood pressure of >140/90 on at least 2 separate occasions before 20 weeks gestation. Chronic hypertension warrants scheduling delivery before labor might start naturally because there is a 2-3 fold increased risk of stillbirth in pregnancies complicated by chronic hypertension. The longer the pregnancy goes on, the higher the risk of stillbirth. On the other hand, there are real risks to infants who are delivered too early, such as needing to be on a mechanical ventilator to breathe or seizures.

The authors of this new study looked back at the records of 683 women with chronic hypertension who were still pregnant at 36 weeks of gestation from 2000-2014. Notably, the study was retrospective and observational- the authors didn't assign people to delivery at certain weeks or follow deliveries as they were happening. For each week of gestation (36, 37, 38, 39, and beyond 39), the authors compared women whose labor was induced or who were scheduled for a cesarean delivery that week with all the women who were expectantly managed until later gestations (delivery not scheduled that week).

The researchers found that babies suffered more complications related to early delivery when delivery was scheduled before 37 weeks gestation. However, the women whose infants were delivered before 37 weeks had more severe disease, even involving baseline kidney disease. This factor likely explains why their infants were delivered earlier and may also explain the increase in neonatal complications. It is impossible to tease apart if the complications were due to the more serious disease or to the earlier delivery. Waiting to deliver the infant past 39 weeks was associated with an increased risk of severe preeclampsia and stillbirth.

Overall, this study contributes to our understanding of optimal timing of delivery for pregnancies complicated by chronic hypertension but does not give a clear-cut answer to the question, "When is the perfect time to deliver the baby?" The pros and cons for delivery timing must be balanced for each patient individually, and likely physicians will continue to struggle with this question for years to come.

We want to hear from you! When do you schedule delivery for chronic hypertension? How do you balance the pros and cons?