Strengths and limitations
The main strength of this study is that all pregnancies included were
fully evaluated and delivered in a single tertiary center, with a long
tradition of vaginal delivery and breech extraction of the second twin.
To our knowledge, this is the first study considering the mode of onset
of labor as well as 2-years-neurodevelopment. Although the study
population is not large, we were able to define more detailed and
accurate perinatal outcome measures than it is possible to do with
registry-based data. Furthermore, this is a primary analysis, and not a
subgroup analysis of a previous larger study.
Though retrospective studies are limited by confounders, it is not
possible to develop this study as a randomized controlled trial for
ethical reasons. In our center, at least two obstetricians and two
neonatologists were always present at birth, and an operating room was
available for emergency CS if required; therefore, the results can be
extrapolated to centers that meet the same conditions.