Placental Thickness in the Second Trimester

he in utero environment and its impact on neonatal health are of increasing interest in relation to adult health outcomes.1,2 There is a growing body of evidence that birth weight and placental insufficiency are important risk factors for later development of the so-called metabolic syndrome: hypertension, diabetes, and coronary heart disease.3 The placenta is the principal influence on fetal birth weight, and it is thought that abnormalities of placental growth may precede abnormalities in fetal growth.4 Because the placenta may be the first organ to manifest changes of disease in pregnancy, placental features may have a role in screening for pregnancy complications. Placental thickness is the easiest placental dimension to measure, yet little is known about the “normal” placental thickness as measured by second-trimester sonography. Historically, a placenta of greater than 4 cm in thickness has been regarded as abnormal5 and associated with various poor outcomes.6,7 However, that idea was based on a study that was performed more than 25 years ago, and there are no current data to support this cutoff value Anna J. Lee, MBBS, FRANZCOG, DDU, Michael Bethune, MBBS, FRANZCOG, DDU, COGU, Richard J. Hiscock, MBBS, FANZCA