Strengths and Limitations
Our study has all the limitations of a retrospective review, and it is
possible that a few donor or recipient cases were mislabeled when the
databases were generated; however, this should not affect the results of
our study since DUAPI represents the absolute intertwin differences in
UA PI. In addition, 6.7% (25/374) of TTTS cases were lost to follow-up
to 30 days, but there were no significant differences in the proportion
of lost to follow-up cases between the DUAPI groups (<0.4 and
≥0.4), which reduces the possibility of selection bias. Similarly, the
proportion of double twin survival to 30 days was not different between
TTTS cases included or excluded in the study based on DUAPI availability
(67% vs. 68.6%; p=0.9), which should also reduce the risk of selection
bias. Strengths of the study are the inclusion of consecutive patients
at two large academic institutions, and the regression analyses
performed, which was adjusted for important confounding variables such
as gestational age at delivery, sFGR, placental location, size of the
trocar, and Quintero staging among others.