Strengths and Limitations
The main limitation of our study is its retrospective observational
design in the second part of the study, which does not account for all
potential co-founders. Secondly, despite incorporated automatic
checkpoints, the computerized database is also prone to human errors.
Thirdly, infertile women were heterogenous regarding indication for
reproductive surgery which might influence the insignificant difference
in preterm delivery in regard to the mode of conception. The main
strength of our study is a novel approach to exploring the effect of
fertility treatment on preterm delivery as a treatment-related adverse
outcome. Using PS matching approach allowed us to balance the treated
and untreated group for some of the main co-founders and also for the
number of co-existing possible risk factors for preterm delivery per
woman making the observational study close to a randomized study.
Therefore, the PS matching approach enables higher control over
cofounding, reduces bias, and adds to higher prediction
estimation20-21. However, the number of outcomes in
our study was low, especially of preterm deliveries < 32
weeks, which might influence the precision of estimation. For that
reason, the result should be treated with caution.