Definition of normal blood pressure at 11 to 14 weeks' gestation according to risk.

Objective: To define normal blood pressure at first trimester of pregnancy by performance for pre-eclampsia prediction.

Method: A cohort study in singleton pregnancies, according to the competing risks model for pre-eclampsia. Blood pressure was measured according to a standardized method at 11 to 14 weeks' gestation.

Results: Among 797 pregnancies included, there were 40 (5.0%, IC95 3.6; 6.4) deliveries with pre-eclampsia. The systolic, diastolic, and mean arterial blood pressures were respectively of 101(9), 68(8) and 79(8) mmHg in pregnant women who did not develop pre-eclampsia, against 109(10), 75(8) and 86(8) in those who did (p < 0.001, t-test). The areas under the curves were 0.707 (0.637; 0.777), 0.728 (0.661; 0.795), and 0.738 (0.673; 0.803). At a 3% of false positive rate, the cut-off points were 119, 83 and 94 mmHg with predictive values of negative of 95.6%.

Conclusions: It is feasible to define the normal values for blood pressure in pregnancy on biostatistic and clinical basis.