Transvaginal sonographic imaging of early second-trimester fetal anatomy assisted by uterine fundal pressure.

OBJECTIVE

To assess the advantage of applying uterine fundal pressure to assist transvaginal sonographic imaging of early second-trimester fetal anatomy.

METHODS

One hundred consecutive patients with singleton fetuses underwent routine transvaginal sonographic assessment of fetal anatomy between 13 and 17 weeks' gestation. If the entire fetal anatomy including cardiac outflow tracts was not depicted, uterine fundal pressure was applied with the operator's nonscanning hand in a bimanual fashion, to facilitate transvaginal imaging. Transabdominal sonography was performed when visualization of the entire fetal anatomy was not obtainable with transvaginal or uterine fundal pressure-assisted transvaginal sonography. Observed fetal structures with and without fundal pressure were compared. Factors assessed that may have modified the value of fundal pressure included patient weight, gestational age, fetal presentation, previous abdominal surgery, and the presence of uterine fibroids. Statistical analysis included McNemar test, chi 2, Fisher exact test, and t test, with P < .05 considered significant.

RESULTS

Visualization of lower limbs, head (including intracranial structures), upper limbs, kidneys, spine, gender, feet, hands (digits), face, four-chamber view, and cardiac outflow tracts was significantly enhanced by uterine fundal pressure-assisted versus nonassisted transvaginal sonography. Uterine fundal pressure improved transvaginal sonographic imaging in 91% of subjects, and in 51% of all subjects, a complete examination was thus obtained. In 20% of all subjects, transabdominal sonography was required to complete the examination. Complete fetal anatomic scanning was unobtainable despite uterine fundal pressure supplemented by transabdominal sonography in 29% of cases. Completion of the transvaginal sonographic fetal anatomic survey with uterine fundal pressure was related to gestational age (P < .02) and maternal weight (P < .05) yet not related to fetal presentation (P = .13), previous abdominal surgery (P = .06), or uterine fibroids (P = .26).

CONCLUSION

Uterine fundal pressure applied during early second-trimester transvaginal sonographic evaluation of fetal anatomy significantly improves visualization of fetal structures otherwise located beyond the effective range of the transvaginal transducer.