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Maternal blood pressure in pregnancy, birth weight, and perinatal mortality in first births: prospective study

BMJ 2004; 329 doi: https://doi.org/10.1136/bmj.38258.566262.7C (Published 02 December 2004) Cite this as: BMJ 2004;329:1312
  1. Philip J Steer (p.steer{at}imperial.ac.uk), professor1,
  2. Mark P Little, senior lecturer2,
  3. Tina Kold-Jensen, lecturer2,
  4. Jean Chapple, honorary senior lecturer2,
  5. Paul Elliott, professor2
  1. 1 Academic Department of Obstetrics and Gynaecology, Imperial College London, Faculty of Medicine, Chelsea and Westminster Hospital, London SW10 9NH
  2. 2 Department of Epidemiology and Public Health, Imperial College London, Faculty of Medicine, London W2 1PG
  1. Correspondence to: P Steer
  • Accepted 14 September 2004

Abstract

Objective To investigate the relation of diastolic blood pressure in pregnancy with birth weight and perinatal mortality.

Design Prospective study.

Setting 15 maternity units in one London health region, 1988-2000.

Participants 210 814 first singleton births of babies weighing more than 200 g among mothers with no hypertension before 20 weeks' gestation and without proteinuria, delivering between 24 and 43 weeks' gestation.

Main outcome measures Birth weight and perinatal mortality.

Results The mean (SD) birth weight of babies born to mothers with no hypertension before 20 weeks' gestation or proteinuria was 3282 g (545 g) and there were 1335 perinatal deaths, compared with 94 perinatal deaths among women with proteinuria or a history of hypertension. Diastolic blood pressure at booking for antenatal checks was progressively higher from weeks 34 to 40 of gestation. The birth weight of babies being delivered after 34 weeks was highest for highest recorded maternal diastolic blood pressures of between 70 and 80 mm Hg and lower for blood pressures outside this range. Both low and high diastolic blood pressures were associated with statistically significantly higher perinatal mortality. Using a linear quadratic model, 94 of 825 (11.4%) perinatal deaths could be attributed to mothers having blood pressure differing from the optimal blood pressure (82.7 mm Hg) predicted by the fitted model. Most of these excess deaths occurred with blood pressures below the optimal value.

Conclusions Both low and high diastolic blood pressures in women during pregnancy are associated with small babies and high perinatal mortality.

Footnotes

  • We thank the midwives who entered the data and the supportive clinicians and data guardians at the participating maternity units.

  • Contributors PJS conceived this study, participated in the data analysis, and wrote the first draft of the paper. He is also the guarantor. MPL refined the hypotheses, directed and carried out most of the data analysis, contributed to the writing of the paper, and took the lead in writing the sections on data analysis. TK-J participated in the formulation of the hypotheses and writing of the paper. JC was responsible for setting up the database and advising about its use and was involved in correcting drafts of the paper. PE advised on the analysis, contributed knowledge about the effects of blood pressure, and participated in the writing of the paper.

  • Funding None.

  • Competing interests None declared.

  • Ethical approval This study was approved by the St Mary's NHS Trust local research ethics committee.

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