Maternal Blood Pressure Adaptation in the First Trimester of Pregnancy

Normal changes in blood pressure during pregnancy are well documented in the second and third trimesters. Little is known about first-trimester changes, particularly compared with preconceptional values. This knowledge might allow for early prediction of conditions such as preeclampsia or intrauterine growth restriction. Prior studies utilized a laboratory setting. We conducted this retrospective study to compare blood pressure readings in early pregnancy with preconceptional values in the clinical setting. The records of 44 healthy normotensive nonsmoking women with a body mass index <30 and an uncomplicated appropriately grown singleton term delivery were reviewed. Preconceptional blood pressures values were compared with values at five periods (weeks 1 to 8, 9 to 16, 17 to 23, 24 to 32, 33 to 40). There was no difference in blood pressure parameters when comparing preconceptional values with period 1. The mean and systolic arterial pressures decreased significantly in periods 2 and 3. We were unable to demonstrate significant change in any blood pressure parameter in the first 8 weeks of pregnancy. This work should be repeated in patients who subsequently develop preeclampsia, spontaneous abortion, or intrauterine growth restriction to determine if early changes might be evident in early pregnancy to identify patients destined to develop pregnancy complications.