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Ultrasound Obstet Gynecol. 2019 Apr 22. doi: 10.1002/uog.20298. [Epub ahead of print]

Impedance to blood flow in the umbilical arteries and infant survival in twin-to-twin transfusion syndrome.

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Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX.
Texas Children's Hospital-Pavilion for Women, Houston, TX.



This study compares infant survival according to patterns of impedance to blood flow in the umbilical arteries (UA) among patients with twin-to-twin transfusion syndrome (TTTS).


This retrospective study included women who underwent laser surgery for TTTS between January 2012 and May 2018 at a single institution. Absolute Inter-twin difference in umbilical artery pulsatility index (DUAPI) was measured prior to laser surgery. Twins with intermittent or persistent absent/reversed UA end-diastolic flow (EDF) were analyzed separately. Infant survival was compared between women with a DUAPI equal or above 0.4 and those below this cutoff as well as between fetuses with intermittent and persistent absent/reversed EDF in the UA. Parametric and non-parametric tests were used for analysis. Regression analyses were performed to determine if these study groups were independently associated with infant survival, while controlling for gestational age at delivery, Quintero staging and other important confounding variables. P <0.05 was considered significant.


A total of 231 TTTS cases underwent laser surgery during the study period. UA Doppler information could be retrieved in 206 patients and delivery information was available in 184 of them. Significant differences in dual twin survival at birth was seen between DUAPI groups [<0.4: 83.9% (78/93) vs.≥ 4: 50% (12/24); p<0.001]. Of note, dual twin survival at birth was higher in patients with intermittent compared to persistent absent/reversed EDF in UA [73% (27/37) vs. 36.7% (11/30); p=0.003]. Regression analysis demonstrated that inter-twin DUAPI <0.4 is associated with increased survival of both twins at delivery (p<0.001) and at 30 days (p=0.002) as well as increased survival of at least one twin at delivery (p=0.009). Similarly, intermittent absent/reversed EDF in UA is associated with increased survival of both twins at delivery (p=0.007) and at 30 days (p=0.015).


Small inter-twin differences in impedance to blood flow in the UA are associated with increased dual infant survival in TTTS. Intermittent absent or reversed EDF in the UA portends better infant survival than when these Doppler abnormalities are persistently observed prior to laser surgery. This article is protected by copyright. All rights reserved.


Doppler; intermittent; laser; pulsatility index; twin-to-twin transfusion syndrome; umbilical artery


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