In MC twins, fetal MRI has been used to assess for brain injury that may occur after fetal intervention or following spontaneous in utero demise of a co-twin [17]. This examination is usually not indicated for uncomplicated multiple gestations. In a study by Kawaguchi et al [13], the incidence of unexpected critical complications in patients with MC diamniotic twin pregnancies was significantly lower in those undergoing weekly US, suggesting that weekly sonographic evaluation for patients with MC diamniotic pregnancy may be more effective for the early detection of impending intrauterine fetal death and/or TTTS. US Cervix Transvaginal US cervix transvaginal evaluation for antepartum surveillance 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 location of placental edge can be performed. Multiple Gestations US Duplex Doppler Fetal Middle Cerebral Artery Fetal MCA Doppler assessment is performed to detect the presence of TAPS [3,50,51]. This can be done at serial surveillance examinations, with US evaluation for TTTS and UA Doppler interrogation, as frequently as indicated by fetal status [9,50]. US Duplex Doppler Fetal Umbilical Artery US duplex Doppler fetal UA is essential for antepartum surveillance of MC twins.
Multiple Gestations. In MC twins, fetal MRI has been used to assess for brain injury that may occur after fetal intervention or following spontaneous in utero demise of a co-twin [17]. This examination is usually not indicated for uncomplicated multiple gestations. In a study by Kawaguchi et al [13], the incidence of unexpected critical complications in patients with MC diamniotic twin pregnancies was significantly lower in those undergoing weekly US, suggesting that weekly sonographic evaluation for patients with MC diamniotic pregnancy may be more effective for the early detection of impending intrauterine fetal death and/or TTTS. US Cervix Transvaginal US cervix transvaginal evaluation for antepartum surveillance 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 location of placental edge can be performed. Multiple Gestations US Duplex Doppler Fetal Middle Cerebral Artery Fetal MCA Doppler assessment is performed to detect the presence of TAPS [3,50,51]. This can be done at serial surveillance examinations, with US evaluation for TTTS and UA Doppler interrogation, as frequently as indicated by fetal status [9,50]. US Duplex Doppler Fetal Umbilical Artery US duplex Doppler fetal UA is essential for antepartum surveillance of MC twins.