Blood pressure dynamics during pregnancy and spontaneous preterm birth
Received 25 October 2006; received in revised form 18 January 2007; accepted 13 March 2007.
Objective
The objective of the study was to examine whether blood pressure in early pregnancy and its rise in the second half of gestation are associated with spontaneous preterm birth in healthy, normotensive, nulliparous women.
Study Design
We included 5167 women with singleton gestation who participated in the World Health Organization Calcium Supplementation for the Prevention of Preeclampsia Trial. Systolic, diastolic, and mean arterial blood pressure and pulse pressure at baseline (12-19 weeks of gestation) and at the midthird trimester (30-34 weeks) were calculated. Rise in blood pressure was the difference between the midthird trimester and baseline. Preterm birth was defined as early preterm (less than 34 completed weeks) and late preterm birth (34-36 weeks).
Results
Women experiencing early or late preterm birth had over 10 mm Hg and 3 mm Hg higher rise, respectively, in systolic, diastolic, and mean arterial blood pressure than women delivering at term. A rise in systolic pressure over 30 mm Hg or diastolic pressure over 15 mm Hg was associated with a statistically significant 2- to 3-fold increase in risk of spontaneous preterm birth.
Conclusion
An excessive rise in either systolic or diastolic blood pressures from early pregnancy to the midthird trimester is associated with spontaneous preterm birth in a dose-response pattern.
aDivision of Epidemiology, Statistics and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD
bNuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, England, UK
cDevelopment and Research Training in Human Reproduction, Department of Reproductive Health and Research, World Bank Special Programme of Research, World Health Organization, Geneva, Switzerland
dDepartment of Obstetrics and Gynaecology, Assiut University Hospital, Assiut, Egypt
eDepartment of Obstetrics and Gynecology, Christian Medical College, Vellore, India
fInstituto de Investigación Nutricional, Lima, Peru
gDepartment of Obstetrics and Gynaecology, Government Medical College and Hospital, Nagpur, India
iCentro Rosarino de Estudios Perinatales, Rosario, Argentina
jDepartments of Obstetrics and Gynecology and Medicine, Pritzker School of Medicine, University of Chicago, Chicago, IL.
Reprints not available from the authors.
This work was supported in part by the National Institutes of Health Intramural Research Program (to J.Z., W.S., and K.F.Y.).
Cite this article as: Zhang J, Villar J, Sun W, et al. Blood pressure dynamics during pregnancy and spontaneous preterm birth. Am J Obstet Gynecol 2007;197:162.e1-162.e6.
ABSTRACT