The investigators will compare the effectiveness of gabapentin to metoclopramide for 1 week among 60 women with hyperemesis gravidarum (HG) in this randomized, double-blinded trial. After completion of the 1-week double-blind phase, subjects will be offered open-label gabapentin with rescue metoclopramide until their symptoms no longer require treatment. Enrollment will occur at the University's at Buffalo, of Rochester and of Wisconsin.

Inclusion Criteria:

1. Have received at least 2 administrations of intravenous (iv) hydration separated by at least 1 week or daily emesis for at least the last 14 days and 1 administration of iv hydration.
2. Have at least one of the following: 2-4+ ketonuria, serum potassium < 3.4mmol, or >5% weight loss from weight upon entry to prenatal care.
3. Have failed therapy with at least one antiemetic.
4. Have fetal ultrasound within 6 weeks prior to enrollment confirming a normal-appearing, intrauterine, singleton pregnancy of gestational age < 16 weeks at time of enrollment.
5. Felt by the patient's obstetrician or emergency room attending physician not to have other medical problems such as bowel obstruction, pancreatitis, biliary colic, or peptic ulcer disease that could be contributing to the patient's symptoms.
6. Be >18 years old and not decided to terminate the pregnancy.
7. Have not received or planning to receive a peripherally inserted central catheter (PIC line).
8. Have a Motherisk-PUQE score of ≥12 for the 24-hour Baseline period.
9. Felt not to have any other significant medical, psychiatric or substance abuse problem that would preclude participation in the study.
10. Denies drinking any alcohol after learning about current pregnancy.
11. Agrees to discontinue any current anti-emetic treatments (including antihistamines, ginger, > 10mg/day vitamin B6, serotonin or dopamine antagonists, anticholinergics, acupuncture, hypnosis, or wrist bands) for the next 4 weeks.
12. Pregnancy not conceived through in-vitro fertilization.
13. Able to understand and comply with the study procedures and give informed consent.

Exclusion Criteria:

None not mentioned under Inclusion Criteria.

1 week of double-blind therapy