Fetal Metabolic Alkalosis Resulting from Maternal Vomiting

We describe a pregnant patient with severe compulsive water ingestion and vomiting that lead to metabolic alkalosis and preterm delivery. A 21-year-old patient was hospitalized multiple times throughout pregnancy for symptoms initially thought to be related to hyperemesis gravidarum. Overtime, it became apparent that the patient induced vomiting by rapidly drinking large volumes of water. At 32 weeks' gestation, rapid ingestion of water caused 3 days of vomiting with findings of hyponatremia, hypokalemia, hypochloremia, metabolic alkalosis, and compensatory respiratory acidosis. Fetal monitoring showed minimal variability and recurrent decelerations; subsequent biophysical profile score of 2/10 prompted urgent cesarean section. A male newborn was delivered and cord blood gases reflected neonatal metabolic alkalosis and electrolyte imbalances identical to those of the mother. Compensatory hypoventilation in both mother and fetus were treated with assisted ventilation. With saline administration and repletion of electrolytes, metabolic alkalosis resolved for both patients within days. Metabolic alkalosis was transplacentally acquired by the fetus. This case demonstrates the development of metabolic alkalosis in a pregnant woman caused by vomiting severe enough to prompt preterm delivery for nonreassuring fetal status. It also demonstrates fetal dependence on both placenta and mother to maintain physiologic acid-base and electrolyte balance.