Placental Thickness -To-Fetal Weight Ratio as a Predictor of Adverse Pregnancy Outcome

The placenta is a vital organ that ensures normal fetal growth and development throughout pregnancy by mediating the exchange of oxygen, nutrients, waste products, and essential hormones between the mother and the fetus (1). Any structural or functional abnormality of the placenta can adversely affect fetal growth and pregnancy outcome, highlighting the importance of placental assessment in antenatal care (2).

Adverse pregnancy outcomes, including intrauterine growth restriction (IUGR), preterm birth, low birth weight, preeclampsia, fetal distress, and perinatal mortality, remain major contributors to maternal and neonatal morbidity and mortality worldwide. Early identification of high-risk pregnancies allows timely interventions, closer surveillance, and improved perinatal outcomes (3). However, advances in ultrasonography and antenatal care, reliable, non-invasive, and easily measurable predictors of adverse outcomes are still limited (4).

Ultrasonographic evaluation of placental morphology has emerged as a practical, non-invasive, and widely accessible method to assess placental health. Among the various parameters, placental thickness reflects placental growth, maturation, and potentially its functional capacity, correlating with gestational age and fetal weight in normal pregnancies. Abnormal placental thickness either decreased or increased has been associated with maternal and fetal pathological conditions (5).

A thin placenta is frequently linked to preeclampsia, IUGR, and chorioamnionitis, whereas a thick placenta defined as more than 3 cm before 20 weeks of gestation and greater than 5 cm at term is observed in Rh-negative pregnancies, gestational diabetes mellitus, and intrauterine infections, particularly primary maternal cytomegalovirus infection (6). Placentomegaly may also be associated with fetal anemia or hromosomal abnormalities such as triploidy, and may result from inflammation, edema, or compensatory hypertrophy secondary to placental insufficiency (7).

Maternal disorders often affect both the fetus and the placenta, making abnormal placental growth a potential marker for impaired fetal growth and adverse neonatal outcomes. Nevertheless, the predictive value of placental thickness alone remains uncertain (8).