Lady Sybil's Death Highlights Killer Eclampsia The country doctor who had known Lady Sybil Crawley since she was a girl first noticed her "muddled" mental state, then her swollen ankles in Sunday night's heartbreaking episode of "Downton Abbey." But her family ignored Dr. Richard Clarkson's warnings to have an emergency C-section, and the kindest character on the wildly popular television show died in a fit of seizures, ultimately unable to breathe. Sybil, the youngest daughter of Lord Grantham, played by Jessica Brown-Findlay, died of eclampsia, the most serious form of preeclampsia -- the world's number one killer of mothers and babies in childbirth. "It was pretty accurate medically," said Dr. Maurice Druzin, chief of obstetrics and gynecology at Lucille Packard Children's Hospital at Stanford University. The local country doctor was clearly correct and the fancy consultant from London was not. After the birth, Sybil falls into convulsions and an agonizing death. "Even today, health care professionals sometimes minimize the symptoms of the disease, although it's much less common than it was before," Druzin said. Preeclampsia, sometimes called toxemia, is out-of-control hypertension in pregnancy and can be particularly dangerous because a woman usually doesn't feel sick. One in 10 women will develop preeclampsia and 1 in 100 will develop the more serious eclampsia, according to the Centers for Disease Control and Prevention. It is a multi-system disorder than can shut down the kidneys or liver, cause blood vessel spasms and even cause the placenta to detach from the uterus. In its worst form -- the eclampsia that the fictional Lady Sybil suffered -- it goes to brain and causes life-threatening seizures. The only way to cure preeclampsia, as Clarkson recommended, is to deliver the baby. "In 1920, it was still very dangerous, as they pointed out, and he couldn't assure her survival," said Druzin."But if she developed seizures, she would definitely die. In the Edwardian period, doctors knew about eclampsia, but it wasn't until a decade later in the 1930s that American doctor began to successfully treat seizures with magnesium sulphate, according to Druzin. Clarkson's most important observations were her "altered mental state" and the small size of the baby, he said. Swollen ankles are common in pregnancy, but with the other symptoms, it suggested eclampsia. "They were aware of it then, but didn't have lot ways to deal with it," Druzin said. Hypertensive disorder, chronic hypertension and preeclampsia can result in placental insufficiency, which in turn can lead to smaller babies and decreased fetal growth. If the placenta cannot keep up with the growth needs, the fetus is smaller and has a higher incidence of cardiovascular problems. The doctor knew enough to call for a urine sample to test for protein, an indicator of preeclampsia. Blood pressure devices may not have been as common then. It was only in the 1930s that doctors began regular monthly prenatal visits, which can detect preeclampsia. Updates to guidelines for detection and a tool kit to manage the disease will be announced by the American College of Obstetrics and Gynecology next month. "Poor Sybil," Druzin said. She developed eclampsia and even the seizure was well done. 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.