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Ambulatory blood pressure in pregnancy and fetal growth
D Churchill1, I J Perry, D G Beevers
1Department of Obstetrics and Gynaecology, Good Hope Hospital NHS Trust, Sutton Coldfield, UK.
Insights
Maternal blood pressure during pregnancy is inversely associated with fetal growth. Higher maternal diastolic blood pressure in mid and late pregnancy correlates with lower birth weight and infant size, impacting long-term cardiovascular health.
Area of Science:
- Obstetrics and Gynecology
- Cardiovascular Health
- Perinatal Medicine
Background:
- Intrauterine growth restriction is linked to adult cardiovascular disease risk.
- The impact of maternal blood pressure on fetal development during pregnancy requires further clarification.
Purpose of the Study:
- To investigate the relationship between maternal ambulatory blood pressure and fetal growth indices.
- To determine if maternal blood pressure during pregnancy influences fetal development.
Main Methods:
- Prospective study of 209 healthy nulliparous pregnant women.
- 24-hour ambulatory blood pressure monitoring at 18, 28, and 36 weeks gestation.
- Exclusion of 8 infants delivered before 32 weeks gestation.
Main Results:
- A 5 mm Hg increase in mean 24-hour diastolic blood pressure at 28 weeks gestation correlated with a 68g decrease in birthweight.
- Similar diastolic pressure increase at 36 weeks gestation was linked to a 76g birthweight decrease.
- Maternal diastolic blood pressure predicted lower ponderal index and head circumference, independent of confounders.
Conclusions:
- A continuous inverse association exists between fetal growth and maternal blood pressure within the normal pregnancy range.
- Maternal blood pressure may be a significant confounding factor in studies linking fetal growth retardation to adult hypertension and cardiovascular disease.
Background:
Retarded growth in utero has been linked with high blood pressure and other risk factors for cardiovascular disease in adult life. However, the influence on fetal growth of the maternal blood pressure during pregnancy is not well defined. In a prospective study, we examined the relation between maternal ambulatory blood pressure during pregnancy and indices of fetal growth.
Methods:
We studied 209 healthy nulliparous pregnant women referred to an inner-city district general hospital (86% of 244 consecutively referred women who met the study criteria). 24 h ambulatory blood-pressure recordings were obtained in early (median 18 weeks [IQR 17-18]) mid (28 weeks [28]), and late (36 weeks [36]) gestation. Eight infants delivered before 32 weeks' gestation were excluded from the analysis.
Findings:
A 5 mm Hg (1 SD) increase in mean 24 h diastolic blood pressure at 28 weeks' gestation was associated with a 68 g (95% Cl 3-132) decrease in birthweight; a similar change in diastolic pressure at 36 weeks' gestation was associated with a 76 g (24-129) decrease in birthweight. These associations were independent of potential confounders (maternal age, height, weight, cigarette smoking, alcohol intake, ethnic origin, pregnancy hypertension syndromes, and preterm birth). Maternal mean 24 h diastolic blood pressure at 28 weeks' gestation was also inversely associated with the infant's ponderal index at birth in multivariate analysis (p = 0.06). Higher maternal ambulatory blood pressure at 28 weeks' and 36 weeks' gestation also predicted lower head circumference, although these associations were dependent on birthweight. Associations between ambulatory systolic blood pressure and indices of fetal growth were weak and inconsistent and ambulatory blood pressure at 18 weeks' gestation did not predict fetal growth.
Interpretation:
There is a continuous inverse association between fetal growth and maternal blood pressure, throughout the range seen in normal pregnancy. Maternal blood pressure may be an important confounding factor in the reported associations between fetal growth retardation and adult hypertension and cardiovascular disease.