What does the placenta have to do with heart disease?
The placenta is a remarkable organ that only had a life span of nine months and yet during that time supports the growing baby before it is ready for extra-uterine life. The placenta itself is a fetal tissue and has a very active role in directing the progress of pregnancy. The mother and fetus have completely separate blood systems so that all nutrients that enter the fetus must be transferred from the maternal to the fetal blood. At the same time the placenta has to prevent the transfer of unwanted toxic substances. The placenta has a specialized outer surface called syncytium that is bathed in maternal blood on the one side and has fetal blood vessels on the other side. It contains a variety of specialized transport proteins that shuttle different nutrients across the placenta in the developing baby.
By the end of pregnancy the placenta had about the same dimensions as a dinner plate yet the shape disguises a highly folded structure inside. In reality it has a very large surface area for uptake of nutrients. Indeed the surface area of the syncytium surface is about 13 square meters, roughly the size of a parking space! This large surface is necessary to support the required oxygen transfer for the fetus. Thus every required nutrient like amino acids, glucose, fats and vitamins has a different mechanism for crossing the placenta.
Why is the placenta so important? Since it is the transport organ for all required nutrients, it is also the bottle neck for fetal growth. The degree that a baby grows before birth is a strong indicator of that person's risk for disease later in life. For example, a baby born at five pounds or below has up to a five times higher risk of having heart disease than a baby born in the eight-to-nine pound range. An abnormal shape of the placenta is also a risk factor for heart disease. Thus, while it was a great surprise for scientists to learn that even the shape of the placenta is influential is determining long-term disease risk, we now know that a healthy placenta gives rise to a healthy baby.