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Pre-pregnancy blood pressure and pregnancy outcomes: a nationwide population-based study
Young Mi Jung1, Gyu Chul Oh2,3, Eunjin Noh4
1Department of Obstetrics and Gynecology, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea.
Insights
Lowering pre-pregnancy blood pressure, even within stage I hypertension, reduces maternal and neonatal complications. This supports applying new hypertension guidelines to pregnant individuals for better outcomes.
Area of Science:
- Obstetrics and Gynecology
- Cardiology
- Public Health
Background:
- Hypertension is a known risk factor for obstetric complications.
- New hypertension guidelines recommend lower thresholds (130-139/80-89 mmHg).
- Limited data exists on pre-pregnancy blood pressure's impact on pregnancy outcomes.
Purpose of the Study:
- To evaluate the effect of pre-pregnancy blood pressure on maternal and neonatal complications.
- To assess if newly defined hypertension thresholds are relevant for pregnant women.
Main Methods:
- Nationwide, population-based study of 375,305 pregnant women without prior hypertension.
- Exclusion of women with pre-pregnancy blood pressure >= 140/90 mmHg.
- Primary outcome: composite morbidity (preeclampsia, placental abruption, stillbirth, preterm birth, low birth weight).
Main Results:
- Stage I hypertension (pre-pregnancy) increased composite morbidity risk (OR 1.68 systolic, 1.56 diastolic).
- A linear association was observed between pre-pregnancy blood pressure and adverse outcomes.
- Risk was highest at newly defined stage I hypertension levels.
Conclusions:
- The "lower, the better" principle applies to maternal and neonatal outcomes.
- Current hypertension diagnostic thresholds may be applicable to pregnant women.
- Pregnant women with stage I hypertension require careful monitoring for adverse outcomes.
Background:
Hypertension has been known to increase the risk of obstetric complications. Recently, the American College of Cardiology endorsed lower thresholds for hypertension as systolic blood pressure of 130-139 mmHg or diastolic blood pressure 80-89 mmHg. However, there is a paucity of information regarding the impact of pre-pregnancy blood pressure on pregnancy outcomes. We aimed to evaluate the effect of pre-pregnancy blood pressure on maternal and neonatal complications.
Methods:
In this nationwide, population based study, pregnant women without history of hypertension and pre-pregnancy blood pressure < 140/90 mmHg were enrolled. The primary outcome of composite morbidity was defined as any of the followings: preeclampsia, placental abruption, stillbirth, preterm birth, or low birth weight.
Results:
A total of 375,305 pregnant women were included. After adjusting for covariates, the risk of composite morbidity was greater in those with stage I hypertension in comparison with the normotensive group (systolic blood pressure, odds ratio = 1.68, 95% CI: 1.59 - 1.78; diastolic blood pressure, odds ratio = 1.56, 95% CI: 1.42 - 1.72). There was a linear association between pre-pregnancy blood pressure and the primary outcome, with risk maximizing at newly defined stage I hypertension and with risk decreasing at lower blood pressure ranges.
Conclusions:
'The lower, the better' phenomenon was still valid for both maternal and neonatal outcomes. Our results suggest that the recent changes in diagnostic thresholds for hypertension may also apply to pregnant women. Therefore, women with stage I hypertension prior to pregnancy should be carefully observed for adverse outcomes.
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