Blood Test Might Warn of Dangerous Complication of Pregnancy

An experimental blood test could one day provide early warning for a life-threatening complication of pregnancy, a new study reports.

Placenta accreta occurs when the placenta — the food and oxygen source for a fetus — grows too deeply into the wall of a woman’s uterus.

The condition can cause a woman to bleed to death following delivery, especially if it hasn’t been detected beforehand, said study leader Dr. Hope Yu, a maternal-fetal medicine specialist at Brigham and Women’s Hospital in Boston.

Unfortunately, up to half of placenta accreta goes undiagnosed prior to delivery, the researchers noted.

The new test appears to accurately detect emerging cases of placenta accreta by looking for microparticle proteins associated with the condition, Yu said.

“This would be something considered to have very good, if not excellent, predictive capability for accreta,” she added.

The placenta typically detaches easily from the wall of the uterus during delivery, but it can’t in placenta accreta because it’s invaded the uterus and, in some cases, even surrounding organs like the bladder.

Placenta accreta occurs in 1 in 272 births, said Dr. Joshua Nitsche, a maternal-fetal medicine specialist at Wake Forest Baptist Medical Center in Winston-Salem, N.C., who reviewed the findings.

“That’s dramatically gone up since the 1980s, when it was about 1 in 1,250, and that has to do with the increasing number of cesarean sections that women have nowadays,” he said. “That’s the No. 1 risk factor” for placenta accreta.

C-sections — or any surgery involving the uterus — can cause the uterine wall to be thinner at incision sites and disrupt the lining of the uterus. “Those things allow the placenta to invade further than normal,” Nitsche said.

One in every 14 women with placenta accreta bleeds to death as a result of delivery, he noted.

No treatment today can prevent or slow the placenta’s invasion into the uterus, Nitsche said.

But if doctors know in advance that a woman has placenta accreta, they can prepare for a complicated delivery, Yu and Nitsche said.

They can make sure that surgeons, anesthesiologists, interventional radiologists and other important specialists are briefed in advance on the expecting mother’s case, Yu said. They can also have plenty of donor blood on hand to replace what she will lose.

Those measures, taken at hospitals experienced in placenta accreta care, can reduce the mother’s risk of death or injury by up to 80%, the researchers explained.

“When you know it’s coming and you can make the proper preparations, the risk of maternal death and serious long-term complications is reasonably low,” Nitsche said.

Unfortunately, between 33% and 50% of placenta accreta cases go undiagnosed prior to delivery, the study authors noted.

“Currently, the diagnosis is made by ultrasound, and the diagnosis can be missed because it’s not exactly straightforward to diagnose it via ultrasound,” Nitsche said.

For this study, researchers compared 35 patients with placenta accreta with 70 who had healthy pregnancies.

They analyzed blood samples taken during the second and third trimesters of pregnancy, to see if there were any differences in circulating microparticle proteins (CMP).

Cells use CMPs to communicate with each other, and these have been studied extensively in cancer detection research.

The researchers identified five second-trimester CMPs and four third-trimester CMPs that could be used to detect placenta accreta.

“The hope is that we could develop this into a test in the future that women who have risk factors for accreta during their pregnancy could universally get in the second trimester,” Yu said. “If their test indicates they are at increased risk, we can ensure that the patient has met with an accreta multidisciplinary care team, making sure that the woman has as stable a delivery as possible.”

This blood panel now needs to be tested and verified in larger groups of pregnant women, Yu and Nitsche said. It will be years before the test could be available as a standard screening tool.

“A test like this would need to be assessed in lots of different patient populations,” Nitsche said. “It worked in that particular hospital with that particular group, but does it work elsewhere with the same sort of sensitivity and specificity?”

The new study was published online Jan. 5 in the journal Scientific Reports.

More information

The Cleveland Clinic has more about placenta accreta.

SOURCES: Hope Yu, MD, maternal-fetal medicine specialist, Brigham and Women’s Hospital, Boston; Joshua Nitsche, MD, PhD, maternal-fetal medicine specialist, Wake Forest Baptist Medical Center, Winston-Salem, N.C.; Scientific Reports, Jan. 5, 2023, online