Background: Cystic hygroma is a congenital lymphatic malformation frequently associated with chromosomal abnormalities, hydrops fetalis, and high fetal mortality. Diagnosed predominantly in the first trimester, late-detected cases often present severe complications and poor prognosis, particularly in low-resource settings with limited access to advanced diagnostic modalities. Case Presentation: We report the case of a 30-year-old third gravida woman in Bangladesh who presented at over 24 weeks’ gestation with amenorrhea and a prenatal ultrasound indicative of cystic hygroma, pleural effusion, and oligohydramnios. Initial ultrasound findings included a large cystic mass at the fetal neck, pleural effusion, and body hyperflexion, suggestive of fetal hydrops and cystic hygroma. Serial ultrasounds confirmed persistent cystic hygroma, increased pleural effusion, and ascites, alongside declining amniotic fluid levels. Limited access to genetic testing restricted comprehensive diagnostic evaluation. The case highlights the high-risk nature of late-diagnosed cystic hygroma, especially where resource constraints limit available interventions. Conclusion: This case underscores the poor prognosis of cystic hygroma in advanced gestation, emphasizing the importance of early screening, regular prenatal visits, and improved access to genetic counseling and non-invasive diagnostic technologies. Future research should prioritize affordable diagnostic tools for low-resource healthcare environments to support timely diagnosis and management.