As an unborn baby develops in the womb, its growth depends on a variety of factors, genetics among them. But sometimes a fetus doesn’t grow as much as is normally expected in relation to its gestational age. This is called intrauterine growth restriction (IUGR) or fetal growth restriction (FGR).
Babies with IUGR may develop health problems such as low resistance to infection. They may also have a hard time handling the stress of a vaginal birth. One possible cause of IUGR is that the fetus is not getting enough nutrients from the placenta.
In order to learn more about the structural differences in placentas in normal versus IUGR pregnancies, scientists at the Ludwig Maximilian University of Munich used Stereo Investigator to image tissue in both cases–finding that there are indeed quantifiable differences between the two.
One main difference is that the villi, the finger-like structures that allow nutrients and oxygen to flow from the mother to the baby, are smaller in volume in IUGR cases. Of the two types of villi present in a pregnancy, only one type—the contractile villi (the ones with muscle cells in their surrounding sheaths) were smaller. There was no difference in size between non-contractile villi in normal and IUGR placentas.

The figure shows Tukey plots of core clinical and gross anatomic data.
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