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. 2021 Apr 27;18(4):e1003611.
doi: 10.1371/journal.pmed.1003611. eCollection 2021 Apr.

International gestational age-specific centiles for blood pressure in pregnancy from the INTERGROWTH-21st Project in 8 countries: A longitudinal cohort study

Lauren J Green  1 , Stephen H Kennedy  2   3 , Lucy Mackillop  2 , Stephen Gerry  4 , Manorama Purwar  5 , Eleonora Staines Urias  2 , Leila Cheikh Ismail  2   6 , Fernando Barros  7 , Cesar Victora  8 , Maria Carvalho  9 , Eric Ohuma  2   4   10 , Yasmin Jaffer  11 , J Alison Noble  12 , Michael Gravett  13 , Ruyan Pang  14 , Ann Lambert  2 , Enrico Bertino  15 , Aris T Papageorghiou  2   3 , Cutberto Garza  16 , Zulfiqar Bhutta  10 , José Villar  2   3 , Peter Watkinson  1 ; International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st)
Affiliations

International gestational age-specific centiles for blood pressure in pregnancy from the INTERGROWTH-21st Project in 8 countries: A longitudinal cohort study

Lauren J Green et al. PLoS Med. .

Abstract

Background: Gestational hypertensive and acute hypotensive disorders are associated with maternal morbidity and mortality worldwide. However, physiological blood pressure changes in pregnancy are insufficiently defined. We describe blood pressure changes across healthy pregnancies from the International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st) Fetal Growth Longitudinal Study (FGLS) to produce international, gestational age-specific, smoothed centiles (third, 10th, 50th, 90th, and 97th) for blood pressure.

Methods and findings: Secondary analysis of a prospective, longitudinal, observational cohort study (2009 to 2016) was conducted across 8 diverse urban areas in Brazil, China, India, Italy, Kenya, Oman, the United Kingdom, and the United States of America. We enrolled healthy women at low risk of pregnancy complications. We measured blood pressure using standardised methodology and validated equipment at enrolment at <14 weeks, then every 5 ± 1 weeks until delivery. We enrolled 4,607 (35%) women of 13,108 screened. The mean maternal age was 28·4 (standard deviation [SD] 3.9) years; 97% (4,204/4,321) of women were married or living with a partner, and 68% (2,955/4,321) were nulliparous. Their mean body mass index (BMI) was 23.3 (SD 3.0) kg/m2. Systolic blood pressure was lowest at 12 weeks: Median was 111.5 (95% CI 111.3 to 111.8) mmHg, rising to a median maximum of 119.6 (95% CI 118.9 to 120.3) mmHg at 40 weeks' gestation, a difference of 8.1 (95% CI 7.4 to 8.8) mmHg. Median diastolic blood pressure decreased from 12 weeks: 69.1 (95% CI 68.9 to 69.3) mmHg to a minimum of 68.5 (95% CI 68.3 to 68.7) mmHg at 19+5 weeks' gestation, a change of -0·6 (95% CI -0.8 to -0.4) mmHg. Diastolic blood pressure subsequently increased to a maximum of 76.3 (95% CI 75.9 to 76.8) mmHg at 40 weeks' gestation. Systolic blood pressure fell by >14 mmHg or diastolic blood pressure by >11 mmHg in fewer than 10% of women at any gestational age. Fewer than 10% of women increased their systolic blood pressure by >24 mmHg or diastolic blood pressure by >18 mmHg at any gestational age. The study's main limitations were the unavailability of prepregnancy blood pressure values and inability to explore circadian effects because time of day was not recorded for the blood pressure measurements.

Conclusions: Our findings provide international, gestational age-specific centiles and limits of acceptable change to facilitate earlier recognition of deteriorating health in pregnant women. These centiles challenge the idea of a clinically significant midpregnancy drop in blood pressure.

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Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: PW holds grants from the National Institute for Health Research; LM and AP are supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC). SG is funded by an NIHR Doctoral Research Fellowship (DRF-2016-09-073). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. LM works part-time for Sensyne Health. PW worked for Sensyne Health. Both have share options in Sensyne Health; ZB is a member of the Editorial Board of PLOS Medicine; no other relationships or activities that could appear to have influenced the submitted work.

Figures

Fig 1
Fig 1. Flow diagram illustrating women enrolled in FGLS.
FGLS, Fetal Growth Longitudinal Study.
Fig 2
Fig 2. SSD for systolic blood pressure in the FGLS of the INTERGROWTH-21st Project.
FGLS, Fetal Growth Longitudinal Study; SBP, systolic blood pressure; SD, standard deviation; SSD, standardised site difference.
Fig 3
Fig 3. SSD for diastolic blood pressure in the FGLS of the INTERGROWTH-21st Project.
DBP, diastolic blood pressure; FGLS, Fetal Growth Longitudinal Study; SD, standard deviation; SSD, standardised site difference.
Fig 4
Fig 4. Smoothed centiles for systolic and diastolic blood pressure in mmHg; third, 10th, 50th, 90th, and 97th centiles.
Fig 5
Fig 5. Changes from baseline for both systolic and diastolic blood pressure from 16 weeks’ gestation for third, 10th, 50th, 90th, and 97th centiles.
See this image and copyright information in PMC

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