This study proposes to look at the pharmacokinetics of two drugs (Cefazolin and ondansetron) given routinely to pregnant women who are planning to deliver via cesarean section. The investigators will evaluate the metabolism of both drugs by the pregnant woman, the placental transfer over time, and the subsequent metabolism of the transferred drug in the neonate.

There is very little data on drug metabolism during pregnancy, and how it may differ from the non-pregnant woman. There is even less data on placental transfer of drug to the neonate when medications are given prior to delivery. This study proposes to look at the pharmacokinetics of two drugs (Cefazolin and ondansetron) given routinely to pregnant women who are planning to deliver via cesarean section. The investigators will evaluate the metabolism of both drugs by the pregnant woman, the placental transfer over time, and the subsequent metabolism of the transferred drug in the neonate.

The investigators hope to learn 1) the pk profile of both drugs in pregnancy, and how it differs from the non-pregnant woman, 2) the placental transfer of both drugs, and 3) the profile of neonatal metabolism of the drug that crosses the placental barrier.

Inclusion Criteria:

Adult participant:

• Age 18-45 years old
• Term pregnancy (37-42 weeks)
• Delivers by planned cesarean section, or unplanned, non-urgent cesarean section.
• Generally healthy
• Able and willing to sign informed consent

Neonatal participant:

• Male of female
• 37-42 weeks gestation

Exclusion Criteria:

• Adult:Medical condition that would effect metabolism of the study drugs
• Known allergy to either study medication
• Use of medications in the last 48 hours that might induce or inhibit metabolism of ondansetron (e.g. barbiturates, fluconazole, erythromycin, etc.)

Generally health women at 37-42 weeks gestation, and their newborns.