This is a woman who presented for a routine antenatal at 19 weeks of gestation. Serial ultrasounds were performed after that and the following images demonstrated a dumbbell-shaped cystic structure that extended both in the chest and in the abdomen:

As the gestation progressed, the abdominal portion enlarged faster then the chest portion:

The original suspicion was a bronchogenic cyst, but the extension and growth of the abdominal portion brough this diagnosis into question. Nevertheless, after delivery, this child was operated upon and a Bronchogenic cyst  was removed: