M-sign in middle cerebral artery Doppler in twin-to-twin transfusion syndrome – A retrospective cohort study

Abstract

Purpose

In twin-to-twin transfusion syndrome (TTTS), unbalanced vascular anastomoses lead to a net transfer of fluid from the donor to the recipient. This triggers compensatory mechanisms resulting in fetal vasoconstriction. Hemodynamic modelling has shown that the appearance of a second systolic peak P2, in addition to the main systolic peak P1, in the middle cerebral artery (MCA) Doppler waveform, thus creating a systolic M-sign, may indicate increased fetal vasoconstriction. Hence, the M-sign could be expected in twins with TTTS. The Quintero staging system has been used to stage TTTS. However, TTTS does not always develop in line with the Quintero stages and/or the criteria are not always fulfilled. This study investigates whether the M-sign could be an additional TTTS criterion indicating significant imbalance between the fetuses.

Methods

38 women who underwent fetoscopic laser coagulation (FLC) for TTTS were included. The MCA Doppler waveforms were retrospectively analyzed for the presence of an M-sign. We subdivided the M-signs into 2 groups: Group A: the main systolic peak P1 dominates P2, i.e., P2/P1 <1; Group B: P2 exceeds P1: P2/P1 >1.

Results

Before FLC, an M-sign was found in 17/38 (45%) pregnancies. Both twins showed M-signs in 9 pregnancies, only the recipient in 6, and only the donor in 2. In 6 (35%) fetuses, an M-sign appeared before the Quintero criteria were fulfilled. Postoperatively, M-signs disappeared in all cases.

Conclusion

The appearance of an M-sign could be an additional marker of cardiovascular imbalance in monochorionic-diamniotic twins with developing or already present TTTS. Postoperative M-sign disappearance may indicate fetal recovery.

Zusammenfassung

Ziel

Beim fetofetalen Transfusionssyndrom (FFTS) kommt es zum Volumen-Ungleichgewicht zwischen den Feten, welches kompensatorisch zu einer fetalen Vasokonstriktion führt. In hämodynamischen Modellen tritt im Falle einer erhöhten fetalen Vasoaktivität ein zweiter systolischer Peak, P2, zusätzlich zum ersten systolischen Peak, P1, als M-Zeichen in der Dopplerkurve der fetalen Arteria cerebri media (MCA) auf. Daher könnte ein M-Zeichen auch bei Zwillingen mit FFTS auftreten. Die FFTS-Stadien-Einteilung erfolgt seit 1999 mittels der Quintero-Kriterien. Das FFTS entwickelt sich jedoch nicht immer chronologisch und/oder es sind nicht immer alle Kriterien erfüllt. Ziel dieser Studie ist es, das M-Zeichen als zusätzlichen Marker des Volumen-Ungleichgewichtes zwischen den Feten zu untersuchen.

Methode

Es wurden 38 Schwangere nach Lasertherapie aufgrund eines FFTS eingeschlossen. Die MCA-Dopplerkurven wurden retrospektiv auf ein M-Zeichen hin untersucht. Zusätzlich wurden die M-Zeichen in 2 Gruppen unterteilt; Gruppe A: P1 dominiert P2 (P2/P1<1). Gruppe 2: P2 ist größer als P1 (P2/P1 >1).

Ergebnisse

In 17/38 (45%) Schwangerschaften wurde ein M-Zeichen beobachtet: In 9 Schwangerschaften bei beiden Zwillingen, in 6 beim Akzeptor und 2 beim Donor. In 6 Fällen (35%) war das M-Zeichen vorhanden, bevor die Quintero-Kriterien erfüllt waren. Nach Lasertherapie verschwand das M-Zeichen in allen Fällen.

Schlussfolgerungen

Das M-Zeichen kann ein zusätzlicher Marker für ein kardiovaskuläres Ungleichgewicht bei Mo-Di-Zwillingsschwangerschaften darstellen – das postoperative Verschwinden des M-Zeichens wiederum ein Indikator für fetale Erholung.

Keywords

middle cerebral artery - Doppler - TTTS - twins - M-sign

Publication History

Received: 22 July 2024

Accepted after revision: 27 February 2025

Article published online:
02 June 2025

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