High blood pressure during pregnancy is associated with adverse perinatal outcomes

In a recent cohort study published in the journal Hypertension Research, researchers from Japan investigated the link between blood pressure (BP) control and potential adverse outcomes in the perinatal period.

They found that uncontrolled as well as high BP during pregnancy were associated with a greater risk of adverse perinatal outcomes.

Study: The association between blood pressure control in women during pregnancy and adverse perinatal outcomes: the TMM BirThree Cohort Study. Image Credit: chalermphon_tiam/Shutterstock.com

Background

Hypertension is commonly encountered during gestation and complicates about 10% of pregnancies globally.

Hypertension and related disorders are known to increase the risk of unfavorable perinatal outcomes such as low birth weight of the offspring, preterm birth, small for gestational age (SGA), neonatal admission, and Apgar score.

Effective BP management is, therefore, crucial, especially during pregnancy. Recent changes in contraindications for certain medications in Japan have broadened the range of available therapies for controlling BP during pregnancy.

However, existing guidelines provide inconsistent recommendations regarding target BP levels for optimal outcomes. Therefore, the present study aims to examine the association between BP control strategies and specific adverse perinatal conditions, providing evidence for refining clinical approaches to hypertension management during pregnancy.

About the study

The present study was conducted as a part of the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study (TMM BirThree Cohort Study). A total of 18,155 mother-offspring pairs in Miyagi Prefecture, Japan, were included in the analysis.

Women with incomplete data (on medical history, medications, gestational weeks at birth, child’s birth weight, and sex, among others) or multiple pregnancies, abortions, or stillbirths were excluded.

Based on BP after 20 weeks of gestation and antihypertensive drug use, pregnant women were categorized into groups, namely “normal BP” (n = 17,476), “high BP” (n = 604), “controlled BP” (n = 42), and “uncontrolled BP” (n = 33).

The “normal BP” group had BP <140/90 mmHg without using antihypertensive drugs, the “high BP” group had BP ≥140/90 mmHg without using antihypertensive drugs, the “controlled BP” group used antihypertensive drugs and had BP <140/90 mmHg and the “uncontrolled BP” group used antihypertensive drugs and had BP ≥140/90 mmHg.

Systolic and diastolic BP data were extracted from medical charts. Adverse perinatal outcomes, including SGA (birth weight in percentiles 1 to 10), low birth weight (<2,500 g), preterm birth (<37 gestational weeks), neonatal admission, and Apgar scores at 1 and 5 min of birth (<7), were assessed.

Statistical analysis included using a chi-squared test, analysis of variance, and Fisher’s exact test. Two models for logistic regression analyses were used to explore the associations between BP groups and outcomes.

The aim of the study was to provide insights into the impact of BP management in pregnancy on perinatal outcomes, thereby shedding light on potential areas for intervention and care to improve maternal and neonatal health outcomes.

Results and discussion

Women using antihypertensive drugs were found to be older with higher pre-pregnancy BMI. While less than 1% of women used antihypertensive drugs in normal/high BP groups, women in the controlled and uncontrolled BP groups used them in the year before pregnancy as well as in the first and second trimesters.

High BP was significantly associated with a higher SGA prevalence than normal BP. However, the controlled BP group did not show a significant association with SGA.

Further, high, controlled, and uncontrolled BP during pregnancy were associated with increased risks of low birth weight and preterm birth, as compared to normal BP. As per the study, high BP during pregnancy was found to be associated with an increased risk of neonatal ward admission in model 1.

Additionally, high BP was found to be associated with a higher risk of admission to the neonatal intensive care unit (NICU) or growing care unit (GCU), while controlled and uncontrolled BP showed non-significant associations, shown using adjusted odds ratios (ORs).

Compared to normal BP, the adjusted ORs for a 1-minute Apgar score <7 were 1.17 for high BP, 2.23 for controlled BP, and 0.91 for uncontrolled BP.

Ethnic variations have been reported in hypertension during pregnancy. Additionally, the use of antihypertensive drugs is relatively lower in Japan and Korea as compared to other countries.

However, given the change in trends of antihypertensive drug selection observed in the last decade, researchers highlight the need for continued research on trends and risk of complications in Japan and Asia.

Conclusion

In conclusion, the findings provide evidence that both uncontrolled and high BP are linked to increased risk of adverse perinatal outcomes.

Therefore, maintaining blood pressure below 140/90 mmHg in pregnant women is crucial for preventing adverse outcomes for the mother and child.