Natural History of Fetal Non‐Nuchal Lymphatic Malformations: A Single Center Retrospective Study

Objective To document the natural history and complications of second‐ and third‐trimester non‐nuchal lymphatic malformations (LM) and identify predictors of these complications. Methods We conducted a single‐centre retrospective review of fetuses diagnosed with LMs between January 2015 and January 2024. Lesion size was quantified using the lymphatic malformation volume ratio (LVR): LVR = 0.523 x width x length x height (cm 3 ) / head circumference (cm). Outcomes and LVR growth trends were analyzed using Student's t‐test and a linear mixed‐effects model. Results Eighteen cases were included (10 cervical, 8 axillary). Uncomplicated cervical LMs grew at 0.3 cm 2 /week ( p < 0.001). Intralesional bleeding ( n = 3) was associated with LVR > 11 cm 2 and significantly higher growth rates (2.6 vs. 0.3 cm 2 /week; p = 0.005). All cases with LVR > 5 cm 2 required subsequent tracheostomy after birth. Axillary LMs grew at 0.21 cm 2 /week. One case with bleeding had LVR 4.4 cm 2 . Median LVR was significantly lower in vaginal deliveries compared with complicated births (2.0 vs. 7.3 cm 2 ; p = 0.03). All LVR > 4 cm 2 led to delivery complications. Conclusion Higher LVR predicts haemorrhage and airway intervention in cervical LMs, and delivery complications in axillary LMs. These exploratory observations warrant confirmation in larger prospective cohorts.