Prognostic value of absolute versus relative rise of blood pressure in pregnancy

This study evaluated the prognostic value of absolute versus relative rise in blood pressure during pregnancy at the Department of Obstetrics and Gynaecology, University of Nigeria Teaching Hospital, Enugu, Nigeria from 17th December 1997 to 31st March 1999. The study sample consisted of 515 consecutive healthy antenatal subjects of the hospital who satisfied the inclusion criteria. The study involved a longitudinal measurement of variables such as blood pressure and anthropometric data of the subjects as well as the maternal mortality rate, caesarean section rate, incidence of eclampsia and proteinuria, perinatal mortality rate, incidence of severe asphyxia and low birth weight, mean birth weight, birth length, ponderal index and gestational age at delivery. Differences in these indices between different groups of the subjects were compared using the chi-square test for categorical variables and one way ANOVA for continuous variables. Grouping was based on the absolute systolic/diastolic blood pressure (SBP/DBP) and relative rise in SBP/DBP from mind-pregnancy until delivery at term. The absolute blood pressure of 140/90 mmHg was a better predictor of feto-maternal outcome than a relative rise in the systolic/diastolic blood pressure from mid pregnancy, which did not reach this absolute level. We conclude that in the Nigerian obstetric population, the practice of diagnosing pregnancy hypertension on the basis of a relative blood pressure rise of 30/15 mmHg alone without reference to the absolute blood pressure level needs to be reviewed.