US Cervix Transvaginal US cervix transvaginal evaluation for antepartum surveillance for all multiple gestations is useful for assessing cervical length, vasa, and placenta previa. Any cervical pathology, such as myoma or other masses, that may preclude vaginal delivery should also be assessed. Usually, a transabdominal examination is performed first, followed by transvaginal imaging if the initial evaluation is inadequate. Historically, reports suggested measuring cervical length at each visit to triage for risk of preterm labor. However, more recent literature has questioned the significance and usefulness of this practice, recommending against cervical length measurement after 26 weeks. In twin pregnancies, cervical length measuring <1.5 cm has been shown to be predictive of preterm labor, regardless of management strategies [43]. If placenta previa or low-lying placenta has been suggested previously, assessment of the location of placental edge can be performed. US Duplex Doppler Fetal Middle Cerebral Artery For DC twins and multichorionic multiples, if there is a risk for fetal anemia or fetal hydrops is noted during surveillance, fetal MCA Doppler can be performed and interpreted using established nomograms. US duplex Multiple Gestations Doppler fetal MCA can be useful for surveillance of complicated DC or multichorionic gestations when there is concern for fetal anemia. Prognostic importance of MCA-PSV for outcome after laser ablation for TTTS has been reported. In a study by Trieu et al [74], there was no correlation between the incidence of elevated MCA-PSV before laser and fetal survival up to 7 days after laser. In contrast, the presence of an MCA-PSV above 1.5 MoM in the former donor twin 48 hours following laser was associated with higher risk for intrauterine fetal demise of the former donor within a week after surgery [74]. US duplex Doppler fetal UA is essential for antepartum surveillance of complicated MC twins.
Multiple Gestations. US Cervix Transvaginal US cervix transvaginal evaluation for antepartum surveillance for all multiple gestations is useful for assessing cervical length, vasa, and placenta previa. Any cervical pathology, such as myoma or other masses, that may preclude vaginal delivery should also be assessed. Usually, a transabdominal examination is performed first, followed by transvaginal imaging if the initial evaluation is inadequate. Historically, reports suggested measuring cervical length at each visit to triage for risk of preterm labor. However, more recent literature has questioned the significance and usefulness of this practice, recommending against cervical length measurement after 26 weeks. In twin pregnancies, cervical length measuring <1.5 cm has been shown to be predictive of preterm labor, regardless of management strategies [43]. If placenta previa or low-lying placenta has been suggested previously, assessment of the location of placental edge can be performed. US Duplex Doppler Fetal Middle Cerebral Artery For DC twins and multichorionic multiples, if there is a risk for fetal anemia or fetal hydrops is noted during surveillance, fetal MCA Doppler can be performed and interpreted using established nomograms. US duplex Multiple Gestations Doppler fetal MCA can be useful for surveillance of complicated DC or multichorionic gestations when there is concern for fetal anemia. Prognostic importance of MCA-PSV for outcome after laser ablation for TTTS has been reported. In a study by Trieu et al [74], there was no correlation between the incidence of elevated MCA-PSV before laser and fetal survival up to 7 days after laser. In contrast, the presence of an MCA-PSV above 1.5 MoM in the former donor twin 48 hours following laser was associated with higher risk for intrauterine fetal demise of the former donor within a week after surgery [74]. US duplex Doppler fetal UA is essential for antepartum surveillance of complicated MC twins.