Preeclampsia, with high blood pressure and protein in the urine, develops late in the second or third trimester. Possible causes include autoimmune disorders, blood vessel problems, diet or heredity. Women who are over 35, pregnant with twins or who are obese are at greater risk.
The disease can also run in families.
Preeclampsia can also be present in the six weeks post-partum, according to ob/gyn Dr. Jenn Ashton, who is ABC's senior medical contributor.
"It's something that pregnant women need to realize and some ob's miss it," said Ashton, who has seen several cases.
"Even after you have delivered, if you get a severe headache or dizziness or start seeing spots, or all of a sudden you get dramatic edema (swelling) in the legs, you need go to the emergency room," she said.