What is the management approach for a pregnant woman in her second or third trimester with fetal umbilical vein varix?

Management of Fetal Umbilical Vein Varix

For a pregnant woman with fetal umbilical vein varix diagnosed in the second or third trimester, perform a comprehensive fetal anatomic survey and echocardiogram to exclude associated anomalies, then institute weekly surveillance with serial ultrasounds and umbilical artery Doppler, with planned delivery at 36-37 weeks of gestation or earlier if fetal distress develops. 1, 2, 3

Initial Diagnostic Workup

When fetal umbilical vein varix is identified, the priority is determining whether this is an isolated finding or associated with other structural or chromosomal abnormalities:

• Perform a detailed fetal anatomic survey focusing on cardiac and other structural anomalies, as 35% of cases have associated fetal anomalies 4
• Obtain fetal echocardiography to assess for cardiac defects, which are among the most common associated findings 4
• Rule out isoimmunization (particularly Kell), as this has been reported in association with umbilical vein varix 4
• Consider karyotyping or chromosomal microarray if other structural anomalies are present, as chromosomal abnormalities occur in a subset of cases 4

The distinction between isolated and non-isolated umbilical vein varix is critical, as isolated cases have significantly better outcomes, with 48% having completely normal pregnancies and neonatal outcomes 4

Surveillance Protocol

For isolated fetal umbilical vein varix, implement intensive fetal monitoring:

• Weekly ultrasound surveillance from diagnosis until 28 weeks of gestation 3
• Twice-weekly surveillance from 28 weeks until delivery 3
• Weekly umbilical artery Doppler assessment if fetal growth restriction develops 1
• Monitor for turbulent flow within the varix, as this correlates with larger maximal varix size, earlier delivery, and lower birthweight 3
• Assess for thrombosis at each surveillance visit, as this is the primary feared complication that can lead to fetal demise 5

The rationale for intensive surveillance is that while isolated umbilical vein varix can have favorable outcomes, the risk of sudden fetal compromise from thrombosis necessitates close monitoring 2, 6

Timing of Delivery

The optimal delivery timing balances the risk of prematurity against the risk of in utero fetal demise from thrombosis:

• Plan delivery at 36-37 weeks of gestation for isolated umbilical vein varix without complications 3
• Deliver immediately if any signs of fetal distress develop, regardless of gestational age 2, 3
• Administer antenatal corticosteroids if delivery is anticipated before 34 weeks 6

The evidence strongly contradicts older recommendations for routine preterm delivery at 32-34 weeks. A case series of 23 fetuses with isolated umbilical vein varix demonstrated that preterm induction was associated with significantly increased cesarean rates and neonatal morbidity (p=0.015 and p=0.029 respectively), with no cases of intrauterine fetal demise when pregnancies were managed expectantly to term 6. This represents the most recent high-quality evidence on timing of delivery.

Adjunctive Therapies

Consider low-dose aspirin prophylaxis:

• One small case series reported successful use of low-dose aspirin until 35 weeks of gestation to prevent thrombosis, with no cases of varix thrombosis and good neonatal outcomes in all four cases 5
• However, this approach lacks robust evidence and should be discussed as an option rather than standard care 5

Mode of Delivery

Vaginal delivery is appropriate for isolated umbilical vein varix:

• Mode of delivery was not associated with gestational age at diagnosis, size of varix, or flow characteristics 6
• Cesarean delivery should be reserved for standard obstetric indications 6
• The cesarean rate in expectantly managed cases was only 17% 6

Key Pitfalls to Avoid

• Do not routinely induce preterm delivery at 32-34 weeks for isolated umbilical vein varix, as this increases neonatal morbidity without clear benefit 6
• Do not miss associated anomalies by failing to perform comprehensive fetal survey and echocardiography, as 35% have other structural defects 4
• Do not assume all umbilical vein varices have poor prognosis, as isolated cases have favorable outcomes when managed expectantly to near-term 6