RESUMEN
BACKGROUND: Some women's cervices cannot be evaluated because they are obscured by obesity or vertex-presenting fetuses. Measuring cervical length in these cases is difficult or impossible. TECHNIQUE: We hypothesized that the problem of obscured cervices on transabdominal ultrasound could be resolved by introducing sterile water into the vagina, creating a hydroacoustic window between the vaginal lumen and the cervix. Women with unmeasurable cervices on transabdominal ultrasound had repeat studies after introduction of 60 mL of sterile water into their vaginas, and cervical length measurements taken were compared with those made on transvaginal scans. EXPERIENCE: Six pregnant women were studied (four singleton, one twin, and one triplet pregnancy). In all cases, previously unidentifiable cervices were seen adequately. No complications were noted. Statistical analysis (kappa 0.66) suggested good correlation between transabdominal cervical hydrosonography and transvaginal measurements of cervical length. CONCLUSION: Introducing water into the vagina at transabdominal ultrasound can make an obscured cervix visible and measurable.