The incidence of obesity is rising rapidly worldwide with the consequence that more women
are entering pregnancy overweight or obese. This leads to an increased incidence of clinical complications
during pregnancy and of poor obstetric outcomes. The offspring of obese pregnancies are often
macrosomic at birth although there is also a subset of the progeny that are growth-restricted at term.
Maternal obesity during pregnancy is also associated with cardiovascular, metabolic and endocrine dysfunction
in the offspring later in life. As the interface between the mother and fetus, the placenta has a
central role in programming intrauterine development and is known to adapt its phenotype in response
to environmental conditions such as maternal undernutrition and hypoxia. However, less is known about
placental function in the abnormal metabolic and endocrine environment associated with maternal obesity
during pregnancy. This review discusses the placental consequences of maternal obesity induced
either naturally or experimentally by increasing maternal nutritional intake and/or changing the dietary
composition. It takes a comparative, multi-species approach and focusses on placental size, morphology,
nutrient transport, metabolism and endocrine function during the later stages of obese pregnancy. It also
examines the interventions that have been made during pregnancy in an attempt to alleviate the more
adverse impacts of maternal obesity on placental phenotype. The review highlights the potential role of
adaptations in placental phenotype as a contributory factor to the pregnancy complications and changes
in fetal growth and development that are associated with maternal obesity.
Keywords: Obesity, placenta, development, programming, pregnancy, gestational diabetes.
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