Maternal-infant health research will bring placenta into view

placental health
A pre-1858 schematic of the placental circulation from Gray’s Anatomy (Wikimedia Commons).

The afterbirth has generally been an afterthought, but that’s about to change.

This week, 19 research centers were awarded grants from NIH’s Human Placenta Project, which is seeking to learn more about the intricate organ that sustained us in the womb, the interface between us and our mothers.

A robust placenta is key to a healthy pregnancy and baby, but strangely, not much is actually known about it. “It’s a fascinating but very poorly understood structure,” says P. Ellen Grant, MD, who directs the Fetal-Neonatal Neuroimaging and Developmental Science Center at Boston Children’s Hospital and is leading one of the projects.

Sponsored by the National Institute of Child Health and Human Development, the Human Placenta Project is seeking to develop tools to monitor placental health and study the effects of environmental factors. The imaging study Grant is leading will look for differences in the placenta that might help explain why obese mothers have more pregnancy complications—including a more than doubled rate of stillbirths.

The four-year, $4.8 million project brings together imaging experts from Boston Children’s, the heads of obstetrics/maternal-fetal health at Brigham and Women’s Hospital and Massachusetts General Hospital, a placental pathologist and technical teams from MIT and the Martinos Center for Biomedical Imaging. The team chose to focus on obesity because of its epidemic proportions and its association with increased risks for both mother and fetus. These risks can be life-long and many are thought to be related to abnormal placental function.

“Obesity may be associated with abnormal nutrient transport across the placenta and altered placental vascular development,” says Grant. “But to be honest, there’s not a lot of hard data on how placental function is altered in real time throughout pregnancy.”

placental health research
The human placenta is a highly complex organ—but the least studied. (CameleonsEye/Shutterstock)

Prenatal placental imaging

The team will develop noninvasive, MRI-based imaging techniques to compare placental development in healthy and obese mothers, measuring the placenta’s anatomy, vascular structure, blood flow, oxygenation and nutrient transport to and from the fetus. Most of these parameters aren’t captured well—if at all—by ultrasound. The researchers are well positioned to succeed because they’ve already been measuring many of these parameters in the brain and heart.

Grant expects that mothers in the second trimester of pregnancy, recruited from maternal obesity clinics at MGH and Brigham and Women’s, will begin coming to Boston Children’s for imaging by the end of this year. In the meantime, the team is jump-starting imaging advancements by studying another group of mothers whose babies are small for gestational age through a currently funded Bioengineering Research Partnership and a collaboration with the Madrid-MIT MVisión Consortium.

“It’s been fascinating—we can ask mothers to breathe oxygen while they’re in the MRI scanner, and see oxygen transport in the placenta,” says Grant. “But the image analysis is complicated—the uterus moves, the mother moves and the placenta is squishy.”

Studying glucose transport will be an added challenge. “There are no preliminary data, because no one’s ever done it,” says Grant.

In addition to imaging pregnant mothers, the team will directly measure placentas donated after birth, including those from preterm infants. (With care, placental function can be sustained for several days.)

Why is so little known about the placenta? I’d put money on gender bias, but Grant notes some logistical challenges. “The placenta only exists for nine months and then is usually thrown out,” she says. “It’s hard to model a live placenta, and animal models aren’t necessarily transferable to humans. Also, when a baby is born, you’re seeing the fully developed placenta; it doesn’t necessarily tell you how it functioned during development.”

“We’re starting to think of pregnancy as a complex system—mother, uterus, placenta, fetus—with the father’s genes in there too,” Grant adds. “We need to think in these terms as we move forward and try to improve fetal outcomes.”

Here’s more on the Placenta Project: