The Placenta in Obesity and Diabetes MelLitus

The placenta is a diary of the pregnancy. Its gross and histologic features reflect maternal physiology, uteroplacental blood flow, and fetoplacental demand. Obesity (body mass index of 30kgm^-2, or greater) and diabetes melLitus (preexisting and gestational) are growing problems in our population. In the United States, nearly one in three reproductive age women are obese. Recent data from our university hospital in Oregon revealed that 40% of our patients were obese at the start of their pregnancies. This is significant because obesity is associated with an increased risk of gestational diabetes melLitus (GDM), preterm birth, fetal growth abnormaLities, preeclampsia, and stillbirth. In turn, GDM is more common than a generation ago, with an estimated prevalence of 4-6% in the United States. The impact is significant: Obesity alone increases the risk of stillbirth by threefold, while GDM increases this risk to approximately tenfold.Over the past 25 years it has become increasingly clear that nutritional and stress conditions in the womb are primary drivers of adult-onset chronic disease in the offspring. The modification of a growing fetus that leads to later disease is called 'programming.' The placenta is the gatekeeper that regulates nutritional flow from a mother to her fetus. Therefore, the development and maintenance of the placenta during the whole gestation is a key element in determining the health of the entire population. Unfortunately, the placenta is the least studied of all organs.How obesity and GDM affect placental and fetal growth are only beginning to be understood. This article will discuss the effects of obesity and diabetes on fetoplacental growth, the histopathologic features common to these placentas, the role of spiral artery remodeLing, and how obesity and GDM affect uteroplacental blood flow and placental nutrient transport. The article will end by stating the anticipated impact of the obesity/diabetes epidemic on developmental programming. These mechanisms need to be better understood, and to fully clarify the role of the placenta in the world of chronic disease will require enormous investments in research.