Antenatal register data from 62 clinics in 5 regions of Kenya were used to estimate women with human immunodeficiency virus (HIV) risk (partner HIV status, syphilis). With individual risk-guided preexposure prophylaxis (PrEP) offer in all regions, 39% of pregnant women would be offered PrEP nationally. Offering PrEP to all women in high-prevalence regions reached 26% of the pregnant women.