Related Experiment Video
Updated: Jun 12, 2026

Accurate and Simple Evaluation of Vascular Anastomoses in Monochorionic Placenta using Colored Dye
Published on: September 5, 2011
Monochorionic monoamniotic twin pregnancies with two yolk sacs may not be a rare finding: a report of two cases
T Murakoshi1, K Ishii, M Matsushita
1Division of Perinatology, Fetal Diagnosis and Therapy, Maternal and Perinatal Care Center, Seirei Hamamatsu General Hospital, Naka-ku, Hamamatsu City, Japan. t-murakoshi@sis.seirei.or.jp
Abstract:
The exact determination of amnionicity is a major issue for the clinical management of monochorionic twin pregnancies, due to the high risk of perinatal mortality and morbidity in monochorionic monoamniotic (MCMA) twins. Counting the number of yolk sacs is believed to be a good indicator of amnionicity in the early first trimester, and it has previously been suggested that the number of yolk sacs is equal to amnionicity in both MCMA and monochorionic diamniotic twin pregnancies. However, the accuracy of the relationship between number of yolk sacs and amnionicity has recently been called into question. To the best of our knowledge, no previous reports have shown two yolk sacs in MCMA twin pregnancies. We report two cases of MCMA twins with two yolk sacs on first-trimester ultrasonography, and confirmed monoamnionicity in the second trimester showing umbilical cord entanglement. Postnatal examination showed an MCMA placenta in both cases, and entangled umbilical cords confirmed monoamnionicity. The possibility of monoamnionicity must still be suspected when two yolk sacs are detected early in the first trimester on ultrasound examination in monochorionic twin pregnancies.
Related Concept Videos
Nondisjunction
Nondisjunction
Ovarian Cycle
Case Studies
Meiosis II
Meiosis I
