OBJECTIVES: To assess health care costs associated with a diagnosis of preeclampsia or hypertension during pregnancy by describing 5-month antepartum and delivery, and 3-month postpartum health care costs. METHODS: Pregnancy episodes (1999-2005) for female claimants ages 15-55 who met continuous enrollment criteria were constructed using a U.S. employer-based insurance claims database.  Episodes were stratified based on a diagnosis of preeclampsia (ICD-9 642.4-642.7; N=2,435), hypertension during pregnancy (ICD-9 642.0, 642.1, 642.3, 642.9; N=2,419), or absence of either of these diagnoses (N=39,597).  Pregnancy-related maternal (5-month antepartum and delivery, and 3-month postpartum) and neonatal (3-month postpartum) healthcare costs were compared using nonparametric Wilcoxon rank-sum tests, with mean values reported here. RESULTS: Antepartum and delivery costs were highest for the preeclampsia group ($13,491), followed by the hypertension ($8,899) and comparison ($8,075) groups (between-group differences p<0.001).  Inpatient costs in the preeclampsia group were 58% ($11,031 vs. $6,961; p<0.001) and 63% ($11,031 vs. $6,781; p<0.001) greater than in the hypertension and comparison groups, respectively.  Maternal postpartum medical costs in the preeclampsia, hypertension, and comparison groups were $1623, $1028, and $741, respectively (between-group differences p<0.001).  Neonatal costs in the preeclampsia group were much higher than those in the hypertension and comparison groups ($7035 vs. $2784; p<0.001 and $7035 vs. $2484; p<0.001).  More than 60% of all neonatal costs in the preeclampsia group were associated with neonatal or pediatric intensive care unit (NICU/PICU) services, compared to less than 40% in both the hypertension and comparison groups.  Total maternal and neonatal postpartum costs were $8658, $3812, and $3226, respectively (between-group differences p<0.001). CONCLUSIONS: Pregnancies with a preeclampsia diagnosis are associated with significantly higher maternal antepartum and delivery costs, and all postpartum costs.  Neonatal costs are also significantly higher, largely due to NICU/PICU care of babies born to mothers with a diagnosis of preeclamspia.