Lab-grown mini-placentas reveal clue to why pregnancy complications happen

For the first time, scientists have created detailed maps of immune cells in the placenta, showing how the cells defend the fetus from invaders during early pregnancy.

Such infections can lead to serious complications, such as pregnancy loss and preterm birth, so this knowledge could someday be used to develop treatments that stop these problems from arising, the researchers said.

To create these maps, the researchers used "mini-placentas" grown from 0.15 square inches (1 square centimeter) of placental tissue donated by women who were around six to 14 weeks pregnant at the time. These tiny versions of the placenta were cultured in the lab using growth-inducing chemicals. 

The scientists used the placentas to investigate how three major pathogens infect the organ: the parasites Plasmodium falciparum and Toxoplasma gondii, which cause malaria and toxoplasmosis, respectively; and Listeria monocytogenes, a bacterium responsible for an infection called listeriosis. 

Related: 'Mini placentas' may reveal roots of pregnancy disorders like preeclampsia

The placenta acts as a selective barrier between the mother and developing fetus during pregnancy, meaning it lets some substances, such as nutrients, through while blocking others, such as harmful germs and toxins. This is important, as during the early stages of pregnancy the fetus' immune system is only just beginning to mature.

However, T. gondii and L. monocytogenes can sneakily cross the placenta, while P. falciparum can attach to it. Scientists still don't fully understand how these infections ultimately lead to pregnancy complications, the researchers wrote in a study published Friday (May 3) in the journal Cell Systems.