<p class="first" id="d7047608e111">Initial observational studies and a systematic
review published 5 years ago have suggested
that obstetric and perinatal outcomes are better in offspring conceived following
frozen rather than fresh embryo transfers, with reduced risks of preterm birth, small
for gestational age, low birth weight and pre-eclampsia. More recent primary studies
are beginning to challenge some of these findings. We therefore conducted an updated
systematic review and cumulative meta-analysis to examine if these results have remained
consistent over time.