Objectives: The authors aimed to provide evidence for a major gene effect on blood pressure across normal pregnancy.
Methods: Blood pressure measurements from 265 patients of Mexican descent derived from medical records were grouped into 4-week blocks by gestational age. Analyses of normality in the distribution of measurements for each block were applied to determine the emergence of a major gene effect and identify the gestational age at which that occurs. Systolic and diastolic blood pressures were used to determine median and percentile values for each block.
Results: There was a shift from normal to non-normal distribution in systolic blood pressure between 12 and 15 weeks' gestation. This was similar for diastolic blood pressure. Median blood pressure values increased from 10 to 40 weeks' gestation without evidence of a decline during the second trimester of pregnancy.
Conclusion: Genetic regulation of blood pressure across pregnancy is dynamic, as demonstrated by the emergence of a major gene effect beginning around 12 weeks' gestation.