According to a new study, the number of pregnant women with high blood pressure has soared over the decades.
Between 1970 and 2010, high blood pressure in pregnant women has increased on average by 6 percent each year in the United States.
And it is the leading cause of maternal death in the US.
The study suggests the increase in high blood pressure may be connected to women waiting until they are older to have children.
Researchers also found that hypertension during pregnancy affects black mothers at twice the rate of white mothers.
They are hoping this information will be a step toward figuring out why there is such a difference between races.
Researchers studied CDC records on more than 151 million women between the ages of 15 to 49 who gave birth in a hospital over four decades.
High blood pressure in pregnancy can lead to complications like preeclampsia, stroke, placental abruption, preterm delivery or low birth weight for the baby.