A Systematic Approach to First-trimester Ultrasound Assessment of Twins

Abstract

The incidence of twin pregnancies has increased for the last 20 years mainly as a result of assisted reproduction technologies and pregnancies occurring in older women. Both maternal and perinatal mortality and morbidity are increased in twin pregnancies when compared with singletons. A systematic and detailed first-trimester ultrasound can be a useful tool for detecting chorionicity, growth discordance, and congenital malformations. Prediction of complications at an early stage can help with directing future management and counseling of patients.

Anomalies of the placenta and umbilical cord in twin gestations

“…9,15,16 An early determination of chorionicity and amnionicity is therefore essential to optimize the management pathways in twin pregnancies. [17][18][19][20] The optimal window to determine chorionicity in twins with 98% accuracy is at 7-9 weeks of gestation. 18 Accuracy may be higher for DC twins than MC twins and is related to the gestational age at which the sonographic appearance of the amniotic sac develops.…”

“…[17][18][19] Two distinct placental masses and different fetal gender indicate DC. When only 1 placental mass is visible on ultrasound, the presence of a lambda sign at the insertion of the intertwin membranes is an accurate predictor for DC whereas T sign is the most reliable indicator of MC ( Figure 1).…”

“…When only 1 placental mass is visible on ultrasound, the presence of a lambda sign at the insertion of the intertwin membranes is an accurate predictor for DC whereas T sign is the most reliable indicator of MC ( Figure 1). [17][18][19][20] Measurements of the intertwin membrane thickness and membrane layer count are associated with a lower sensitivity and specificity than the ultrasound features used earlier in pregnancy but can be useful to determine chorionicity during the second trimester of pregnancy when the insertion of the intertwin is less clear. 20 MA is determined by the absence of a dividing membrane between the amniotic sacs.…”

Perinatal Mortality in Multiple Pregnancy

“…Monochorionicity adverse effects, aneuploidy, congenital malformations, growth restriction, single fetal demise and delivery related problems are additional factors for increased perinatal mortality and should be diagnosed as soon as possible. A systematic ultrasound careful exam should be offered to these pregnancies (Hubinont et al, 2010). This chapter illustrates most of the complications of multiple pregnancies and the prevention of perinatal mortality.…”

Screening for Down syndrome in dichorionic twin pregnancies conceived by in vitro fertilization (IVF): a clinical pilot study to confirm the laboratory methods

“…Early sonographic evaluations in twin pregnancies allows for accurate estimation of the expected due day, chorionicity and placenta location/s [2]. Ultrasound imaging also allows for assessment of the relationships between the amniotic sac/s and the cervix and to rule out major fetal structural abnormalities [3][4][5]. Compared to singleton gestations, twins also have an increased risk for chromosomal abnormalities [6,7].…”