Objectives. To strengthen prevention of mother-to-child HIV transmission (pMTCT) pro- gram implementation in La Romana (LR) province, by estimating HIV prevalence and iden- tifying characteristics associated with HIV infection in parturients. Methods. Umbilical cord blood samples were collected at seven obstetrical sites where over 95% of LR’s deliveries occur during four phases (pilot, expanded pilot, full study, and pMTCT program monitoring) from 2 August 2002 to 30 September 2006. Results were linked to data abstracted from delivery records. Results. HIV seroprevalence was 2.6% (263/10 040 overall; 114/4 452, full-study phase (95% confidence interval = 2.1%–3.1%)). Most HIV-infected parturients were Dominican (68.9%) and urban (64.0%). However, prevalence was higher among Haitians (3.7%) than Dominicans (2.3% (p < 0.001)), especially those aged 21–25 years (5.2% vs. 2.3% (p < 0.001)), and among rural, batey, and peri-urban (vs. urban) parturients (3.4% vs. 2.3%, (p = 0.003)). HIV preva- lence was associated with commercial sex work (reported by only 0.4%), and prior pregnancy. In logistic regression analysis, commercial sex work, Haitian nationality, and prior pregnancy were independently associated with HIV infection. Caesarean deliveries were more frequent, and rose in the last years of the study, among HIV seropositives; however, most deliveries among seropos- itives (57.5%) were vaginal. Conclusions. HIV prevalence among LR parturients was higher than the estimated preva- lence in the Dominican Republic (0.8%–1.0%) and, in contrast to past studies, predominantly affected urban Dominicans. HIV prevalence among LR Haitian parturients was higher than among Dominican counterparts and prenatal clinic attendees in Haiti (who had a rate of 3.1%). Consistently implemented, targeted pMTCT interventions are needed.