Review Question - QID 210581

A 38-year-old G1P0 woman presents to her obstetrician for a prenatal visit. She reports feeling well and has no acute concerns. She is currently at 28 weeks gestation previously confirmed by ultrasound. She takes her folate supplements daily. Her temperature is 98.7°F (37°C), blood pressure is 117/68 mmHg, pulse is 67/min, respirations are 11/min, and oxygen saturation is 99% on room air. On physical exam, the uterus is soft and globular. The top of the uterine fundus is found around the level of the umbilicus. A fetal ultrasound demonstrates a reduced liver volume and subcutaneous fat with relative sparing of the head. Which of the following is most likely the cause of this patient's ultrasound findings?