The clinical imperative of placental and cord imaging

The latest chapter in the Obstetrics Module of GLOWM’s Continuous Textbook of Women’s Medicine is arguably the most comprehensive one ever written on ultrasound evaluation of the placenta and cord. Routine obstetric ultrasound often focuses on the fetus, but this chapter underscores that a thorough examination of the placenta, umbilical cord and membranes is critical for optimizing maternal and fetal outcomes. Abnormalities in these structures are a leading cause of stillbirth, and can lead to severe perinatal complications, many of which are preventable with early detection and appropriate management. This proactive approach is particularly vital for a global readership, where timely intervention can dramatically improve prognoses.

Placenta

Location matters – Correctly identifying placental location is a cornerstone of safe obstetric practice. The chapter emphasizes the importance of detecting conditions like placenta previa, which can lead to life-threatening hemorrhage. Ultrasound evaluation, especially transvaginal sonography, is essential for confirming the location of the placenta in relation to the internal cervical os, allowing clinicians to plan for cesarean delivery and avoid the risks of vaginal birth.

Abnormal adherence – A careful assessment for signs of placenta accreta spectrum (PAS) is crucial, especially in patients with prior uterine surgery like a cesarean section. Sonographic markers such as multiple placental lacunae, loss of the retroplacental clear zone and increased vascularity at the bladder–serosa interface should prompt referral to a specialized center. Managing PAS requires a multidisciplinary team and planned delivery to control hemorrhage and prevent maternal mortality.

Umbilical cord

Insertion site – The chapter highlights the importance of evaluating the cord's insertion into the placenta. Abnormalities like a marginal or velamentous cord insertion are significant because the unprotected vessels in velamentous insertion are vulnerable to compression and rupture, particularly during labor. Identifying these conditions antenatally allows for closer monitoring and a carefully planned delivery, often a cesarean section, to prevent fetal compromise and emergent hemorrhage.

Vascular assessment – Also emphasized is the importance of identifying vascular anomalies, such as single umbilical artery (SUA). While a SUA can be an isolated finding, it is frequently associated with an increased risk of other fetal anomalies, including cardiac, renal and chromosomal abnormalities. Detecting SUA should trigger a detailed fetal anatomic survey and consideration for genetic counseling or diagnostic testing.

Amniotic fluid and membranes

Amniotic fluid volume – Abnormalities in amniotic fluid volume, whether polyhydramnios (excessive fluid) or oligohydramnios (insufficient fluid), can signal underlying fetal or maternal pathologies. For instance, oligohydramnios can be a sign of renal abnormalities or placental insufficiency, while polyhydramnios may be associated with conditions like esophageal atresia or uncontrolled maternal diabetes. Ultrasound is the primary tool for measuring amniotic fluid, and identifying these conditions is a prompt for further investigation and management.

The amnion and chorion – The chapter notes that the evaluation of the fetal membranes is also important. For example, in multiple gestations, it is crucial to determine if the placentas are fused and if the fetuses share a single chorion and amnion. This determination of chorionicity and amnionicity is fundamental for managing twin pregnancies and their associated risks, such as twin-to-twin transfusion syndrome.

Written by leading experts in fetal imaging from the USA and Chile, this chapter advocates for a paradigm shift in obstetric ultrasound, urging practitioners to move beyond a fetus-centric view to a holistic evaluation of the intrauterine environment. By mastering the sonographic assessment of the placenta, cord and membranes, clinicians can detect a range of high-risk conditions, leading to proactive management that saves lives and improves long-term outcomes for mothers and their newborns globally.

Explore the full article here: Ultrasound Evaluation of the Placenta, Umbilical Cord and Membranes | Article | GLOWM.