For this study, researchers evaluated CDC records from more than 151 million US births between 1970 and 2010. They found that a woman who became pregnant in 2010 faced a hypertension risk 13 times higher than in 1970.
Researchers were "very surprised" to find that obesity and smoking trends had "virtually no impact" on the hypertension trend.
Instead, study authors attribute much of the rise to the increase in pregnancy later in life.
The study also found the risk of hypertension during pregnancy is roughly twice as high in black women compared to white women.
What It Means to YouIf you are pregnant, high blood pressure can develop even if you never had high blood pressure before, writes William C. Shiel Jr., MD, FACP, FACR, chief editor of MedicineNet. Pregnant women face special risks, including premature delivery, decreased blood flow to the placenta, and future cardiovascular disease.
High blood pressure in pregnancy can lead to preeclampsia, in which protein leaks into the blood from the kidneys, Dr. Shiel says. If not managed, this can develop into seizures in a condition known as eclampsia, which can be fatal to both mother and baby.
The risk of preeclampsia and eclampsia is higher in both pregnant teens and women over 40, writes Melissa Conrad Stöppler, MD, a medical doctor specializing in pathology.
When it is mild, most women have no symptoms of preeclampsia, Dr. Stöppler says. Severe preeclampsia may cause symptoms that include dizziness, headaches, nausea, vomiting, abdominal pain, vision changes, changes in reflexes, altered mental state, fluid in the lungs (pulmonary edema), and a decrease in urine output.
Although there is no known way to prevent preeclampsia or eclampsia, mothers-to-be are more likely to have a good outcome "with prompt recognition and management," she says. "So it is important for pregnant women to have routine health screenings."