An umbilical vein varix (UVV) is a localized widening or dilation of the umbilical vein, a vessel that plays a crucial role in fetal development. It occurs during pregnancy and often presents as benign, though it requires careful medical attention. While UVV can cause concern, advances in prenatal imaging and management have improved understanding and outcomes.
Understanding Umbilical Vein Varix
The umbilical vein is a key component of the fetal circulatory system, carrying oxygenated, nutrient-rich blood from the placenta to the fetus. It travels through the umbilical cord, entering the fetal abdomen and connecting with the liver’s portal system.
A varix is a focal, abnormal enlargement of the umbilical vein. Diagnostic criteria define it as a diameter greater than 9 mm, or at least 50% wider than the non-dilated portion. Some definitions also include a diameter exceeding two standard deviations above the mean for the gestational age. This dilation most commonly occurs in the intra-abdominal segment of the umbilical vein, located between the fetal abdominal wall and the liver. Umbilical vein varix is considered a relatively rare finding, with an estimated incidence ranging from 0.1 to 2.8 per 1,000 pregnancies. Its exact cause is often unknown (idiopathic), though it may sometimes be associated with other factors.
Detection During Pregnancy
An umbilical vein varix is identified during routine prenatal ultrasound examinations. Sonographers and physicians look for a dilated segment of the umbilical vein, appearing as an anechoic, oval-shaped, or rounded mass within the fetal upper abdomen. It is often diagnosed around 29.9 to 32 weeks.
Doppler ultrasound is used to confirm the diagnosis and assess blood flow. It demonstrates continuous venous flow within the dilated area, differentiating the varix from other fetal abdominal cysts. Color and power Doppler further aid in visualizing the varix and evaluating blood flow.
Potential Fetal Considerations
While many cases of umbilical vein varix are isolated findings and result in favorable outcomes, the condition warrants a thorough evaluation due to potential associations. When isolated, meaning no other fetal anomalies are present, the prognosis is generally good, with a low risk of adverse events. However, in cases where other abnormalities are identified alongside the varix, the outlook can be more complex.
Risks include blood clot formation (thrombosis) within the varix, which can obstruct blood flow. Although rare, rupture of the varix is another concern. In some instances, a varix has been linked to fetal hydrops, a serious condition characterized by abnormal fluid accumulation in two or more fetal body areas. Additionally, umbilical vein varix can be associated with other fetal anomalies, such as cardiac malformations, chromosomal abnormalities (including Trisomy 21), and intrauterine growth restriction. These associations underscore the importance of comprehensive evaluation to determine if the varix is an isolated finding or part of a broader condition.
Monitoring and Management
Once diagnosed, medical professionals implement close monitoring throughout the pregnancy. This involves serial ultrasound examinations to track varix size, assess fetal growth, and evaluate amniotic fluid volume. Doppler studies of the umbilical vein and other fetal vessels assess blood flow patterns, including turbulent flow or thrombosis signs.
Fetal echocardiography is frequently recommended to thoroughly examine the fetal heart, especially if there are concerns about cardiac anomalies that may be associated with the varix. Management often involves a multidisciplinary approach, with maternal-fetal medicine specialists guiding the care plan. While most cases do not necessitate early delivery, continuous monitoring can influence decisions regarding the optimal timing and method of delivery in certain situations, particularly if complications like turbulent flow or growth restriction are noted.