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31-07-2011 | Cardiology | Article

BMI, age, parity linked to increased BP in pregnancy


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MedWire News: Obesity, older age, and lower parity are associated with increased mean blood pressure (BP) in pregnant women, UK researchers say.

Hypertension during pregnancy is one of the diagnostic criteria for pre-eclampsia, explain Corrie Macdonald-Wallis (University of Bristol) and co-authors, which is associated with an increased risk for maternal and perinatal mortality.

They investigated which risk factors are associated with hypertension in pregnant women, to better identify those at risk for hypertensive disorders of pregnancy (HDPs).

The researchers examined a median of 14 repeat antenatal BP measurements throughout the pregnancies of 11,789 women with a live-term birth and no evidence of pre-eclampsia or previous hypertension.

The findings, reported in the Journal of Hypertension, showed that in healthy pregnancies, mean systolic (S)BP and diastolic (D)BP decreased gradually until 18 weeks and then rose from 18 weeks onwards, rising more rapidly at 30 weeks and then again at 36 weeks.

Obese women (body mass index [BMI]≥30.0 kg/m2) had a higher SBP at 8 weeks, at a mean of 121 mmHg, than women of normal weight (BMI=18.5-24.9 kg/m2), with a mean SBP of 113 mmHg. Their SBP actually decreased between 18 and 30 weeks, but then rose more rapidly than in normal-weight women between 30 and 36 weeks, before increasing more slowly thereafter. DBP followed the same pattern, apart from between 30 and 36 weeks, when it rose more slowly in the obese than normal-weight pregnant women.

Women aged over 35 years had a faster increase in SBP from 36 weeks onwards than 25-29-year-old women, and women aged less than 20 or 20-24 years had a smaller increase in DBP between 30 and 36 weeks, compared with 25-29 year-old women.

Nulliparous women had a higher SBP at 8 weeks than multiparous women (112 vs 111 mmHg), and their SBP increased more rapidly from 30 weeks, by 0.220 mmHg per week compared with 0.001 mmHg per week. Nulliparous women's DBP also increased from 30 weeks, by 0.557 mmHg per week, whereas that of multiparous women decreased by 0.152 mmHg per week.

The findings suggest "a continuum of BP risk during pregnancy and that interventions aimed at reducing hypertensive disorders of pregnancy should be targeted at all women from early in pregnancy or during preconception counseling," conclude the authors.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Piriya Mahendra

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