Obstetric ultrasound is central to antenatal care, but access remains limited in many low- and middle-income settings. Ultra-portable devices may extend access to basic obstetric imaging and support midwife-led care.

To assess the diagnostic performance of the echOpen O1 ultra-portable ultrasound probe for selected obstetric targets during antenatal follow-up in Senegal.

We conducted a prospective, multicentre pilot diagnostic agreement study in two health facilities in the Sokone health district, Fatick region, from November 2023 to August 2024. Pregnant women at 37 weeks of gestation or more were included. Each participant underwent three ultrasound examinations: two performed by the same midwife using echOpen O1 and a standard ultrasound device in a randomly assigned order, and one blinded echOpen O1 examination performed by a second midwife. Images and short video clips were reviewed by a reference radiologist. Agreement was assessed for foetal number, foetal presentation, foetal cardiac activity and placental location.

Among 221 included women, 214 were analysed. Overall agreement for the core targets between echOpen O1 and standard ultrasound (intra-operator) was 99.5% (95% CI, 98.6–100). Intra-operator agreement was 99.5% (95% CI, 98.6–100) for foetal presentation, 100% (95% CI, 100–100) for foetal number, placental location and foetal cardiac activity. Expert review confirmed intra-operator agreement above 95% for all targets.

The echOpen O1 probe showed performance comparable with standard ultrasound for basic third-trimester obstetric assessments, supporting its potential to strengthen antenatal care in resource-limited settings.