Multiple pregnancies account for 2-3% of live births and involve the presence of more than one fetus in the uterus, presenting unique challenges for both maternal and fetal health. Chorionicity refers to the number of placentas, while amnionicity describes the number of amniotic sacs.
Determining chorionicity and amnionicity is a critical aspect of managing multiple pregnancies, as it helps identify potential risks and guide appropriate care plans. The best time to assess chorioamnionicity is between 10 and 14 weeks of gestation, using ultrasound to examine the inter-twin membrane and placental junction.
In this chapter, you will explore the challenges of detecting chorioamnionicity, which can be particularly difficult in early or late gestation. You will gain insight into the incidence, pathogenesis, and diagnosis of chorionicity and amnionicity. Detection can be achieved by examining:
- The number of placental masses
- The presence and thickness of amniotic membranes
- The T sign and lambda (λ) sign (Figures 1-5)
Additionally, you will learn about other methods for detecting chorionicity and gain an in-depth understanding of the challenges and special considerations involved.
In multifetal gestation, chorionicity and amnionicity can be detected by ultrasound during the first trimester. If a transabdominal ultrasound is inconclusive, high-resolution transducers, including transvaginal ultrasound, should be utilised. Key ultrasound markers to assess include the number of placental masses, the T and lambda signs, the thickness and number of layers in the inter-twin membrane, and the identification of fetal sex.
For more detailed information and to see high-quality ultrasound images, read the VISUOG chapter on Determining Chorionicity and Amnionicity in Multifetal Pregnancies for free throughout October.
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