Pregnant with her second child, Joan didn't make much of her abdominal pain and headaches until her symptoms worsened. By the time she saw her doctor, her blood pressure had spiked to a dangerously elevated level, triggering an emergency Caesarean section.

Joan is one of hundreds of women whose brush with preeclampsia is chronicled at www.preeclampsia.org, the Preeclampsia Foundation's Web site. While her story ended happily, some of the site's heart-wrenching narratives describe fetal deaths and stillborn babies, highlighting some of the harsh truths about this mysterious condition.

Preeclampsia is a disorder typically occurring after 20 weeks of gestation. It is characterized by high blood pressure and excess protein in the urine, known as "proteinuria." It can lead to a severe complication called eclampsia that causes the women to convulse.

Eclampsia can permanently damage a woman's vital organs and, without treatment, lead to coma, brain damage or death of the mother and infant.

Some 5 percent to 8 percent of pregnancies are affected by preeclampsia, and it is responsible for 15 percent of all premature births in the United States, the Preeclampsia Foundation reports.

Sometimes, though, the classic symptoms of preeclampsia aren't present, making diagnosis tricky. A woman may have a single blood pressure reading that is higher than normal before her pressure slips down again, or she may not exhibit proteinuria until later in her pregnancy.

"Sometimes women present with this kind of vague feeling that they're just not feeling well," says Dr. B. Denise Raynor, associate professor in the Division of Maternal-Fetal Medicine at Emory University School of Medicine in Atlanta. "They don't really have abdominal pain, but they're just not feeling well, or their appetite is not as good, and that can be the beginning of what later develops into serious disease.

"If we had a better way - an easy test - for physicians to do that would help confirm the diagnosis, that'd be great, because it really is defined as hypertension and proteinuria, so if you don't have those two together, it's hard to make the diagnosis sometimes," Raynor explains.

Recent research is igniting hope for such a test. Scientists now have identified two proteins that appear to be involved in the development of preeclampsia.

One of these proteins, known as soluble endoglin, rises earlier and more steeply in women who develop preeclampsia, researchers have reported. Levels of another protein, called sFlt1, also increase. It's believed that these two proteins interfere with the growth and function of blood vessels, signaling a spike in the woman's blood pressure.

"We believe they cause the disease by preventing proangiogenic factors from operating, such as vascular endothelial growth factor and TGF beta1, and that leads to damage and dysfunction of the endothelial cells," says Dr. Richard J. Levine, a senior investigator with the epidemiology branch of the U.S. National Institute of Child Health and Human Development. "These are the cells that line the interior of the vascular system and lead to all the clinical conditions that are perturbed in preeclampsia."

These findings raise the possibility of developing a blood test to screen women at risk for preeclampsia. But more studies will be needed before researchers know whether it's worth the trouble and expense of performing such tests, says Levine, lead author of a pivotal study in the New England Journal of Medicine associating the two proteins with preeclampsia.

At the moment, the value of a predictive tool is uncertain, because there's no way to prevent preeclampsia, and treatment options are limited. If a pregnancy isn't very far along, and the woman's symptoms aren't too severe, the doctor may try to buy time by putting her on bed rest and medications. The only way to stop preeclampsia is to deliver the baby. Magnesium sulfate, an anticonvulsant medication, is typically administered intravenously to prevent the woman from having seizures.

Levine is hopeful that new treatments, or ways to prevent the disease, will be developed in the future.

At present, though, many women end up like Joan, failing to recognize head and abdominal pain as signs of preeclampsia. In fact, more than half of all pregnant women are uninformed about the signs and symptoms of the condition, according to a Preeclampsia Foundation survey of more than 1,300 women who had given birth.

Vigilance is key, because preeclampsia can develop or worsen with little notice.

Raynor once had a patient who had two elevated blood pressures a day but otherwise felt fine and wanted to be released from the hospital. But a blood count showed her platelets were falling, a sign of trouble ahead. In a matter of hours, she became very ill.

"Preeclampsia can sometimes do that: You look fine, and then six hours later, you're intubated, and you're really sick, or your kidneys are failing, and your urine output falls off, or your liver's starting to show damage," Raynor cautions. "All of those things can happen."

Learn more:

The Preeclampsia Foundation: www.preeclampsia.org/symptoms.asp#protein/