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Hypertension

Poster Session 1

(343) Timing of delivery in women with pre-existing hypertension and stillbirth risk: A retrospective population-based study

Tuesday, February 13, 2024
10:30 AM – 12:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective:

To evaluate the risk of stillbirth at term, in women with pre-existing hypertension, to determine if earlier induction of labour (IOL) decreases the risk of stillbirth.


Study Design:

A retrospective population-based cohort study was conducted using the CDC’s Fetal Death Public Use Files and linked data from Period Linked Birth-Infant Death Public Use Files, including all births between 2010 and 2019. Maternal and fetal outcomes among deliveries to women with pre-existing hypertension (exposed) were compared to women without pre-existing hypertension (unexposed). Multivariate logistic regression models, adjusted for maternal age, race, education and smoking were used to estimate the risk of stillbirth and the risk of IOL at each gestational age, as of 37 weeks, compared to women without pre-existing hypertension at the same gestational ages.


Results:

Of 39,757,769 births in our cohort, 98.42% were to women without pre-existing hypertension and 1.58% were to women with pre-existing hypertension. Pre-existing hypertension was associated with an increased risk of adverse maternal and fetal outcomes. The incidence of stillbirth amongst the general population experienced a marginal decrease from 1.43 in 2010, to 1.21 in 2019. The risk of stillbirth increased with gestational age in women with pre-existing hypertension compared to women without, of the same gestational age. The most pronounced rises in risk began at 39 weeks (OR 1.92, 95% CI 1.64-1.24), 40 weeks (OR 1.86 95% CI 1.50-2.35) and 41 weeks (OR 2.74, 95% CI 2.30-3.27). In turn, rates of IOL amongst women with pre-existing hypertension were most elevated between 37 and 39 weeks: 37 weeks (OR 2.46, 95% CI 2.43-2.49), 38 weeks (OR 2.84, 95% CI 2.81-2.87), 39 weeks (OR 2.42, 95% CI 2.39-2.44).


Conclusion:

While women with pre-existing hypertension, with no other complications at term, have increased risk of stillbirth as of 39 weeks, American practice has developed such that this population is undergoing preventive IOL earlier (37-39 weeks), reflecting an overall decrease in stillbirths.