Background: Pregnancy complications such as gestational diabetes and pre-eclampsia predict later cardiovascular (CV) outcomes. However, it still is not clear whether pregnancy complications unmask preexisting impairments or instigate lasting injury. If pre-pregnancy and during-pregnancy CV risk factors are strongly correlated, it becomes more plausible that pregnancy unmasks an existing problem than creating a new one.
Methods: Data from the i3C Consortium, a group of studies assessing the relationship between child/adolescent CV risk factors and adult outcomes, were used. 290 women from four cohorts had data on the same risk factor (blood pressure, lipids, glucose) from visits both prior to and during pregnancy. Correlation coefficients between the pre- and during pregnancy measures were calculated, and the mean difference between the measures modeled with adjustment for age, BMI, race, smoking, and study. Differences by gestational age and time between the pre-pregnancy visit and pregnancy visit were also examined.
Results: All measures were strongly correlated at pre- and during-pregnancy visits (p<0.01), with r of between 0.3 and 0.55. The exception was glucose (r=0.11, p=0.15). These relationships held after adjustment for confounders. Interactions with gestational age indicated stronger correlations with measurements taken in the first and second trimesters than the third. The correlation did not differ by the time elapsed between the pre-pregnancy and pregnancy visits.
Conclusions: Pre- and during-pregnancy CV risk factors are moderately well correlated. It is likely that women who develop pregnancy complications enter the pregnancy with higher risk rather than pregnancy inducing new vascular effects.