Frozen embryos are more likely to produce successful, complication-free IVF pregnancies than those that are fresh, research suggests.
Using stored embryos cuts the risk of bleeding in pregnancy, premature birth, and giving birth to an underweight baby by almost a third, a study has found.
The risk of a baby dying at around the time of birth is also reduced by about a fifth.
If the findings are confirmed it could have major implications for the public funding of In-Vitro Fertilisation treatment, as the NHS regards embryo freezing as an extra service patients are expected to pay for themselves. If freezing becomes a routine part of IVF treatment there may be pressure to change this rule.
Scientists made the discovery after analysing data from 11 international studies involving more than 37,000 IVF pregnancies.
In some cases, newly conceived fresh embryos were used. In others, embryos that had been frozen and stored for two to three months were implanted.
Standard practice is to choose the best embryos for fresh transfer, and only freeze those of good enough quality that are spare.
Findings were presented by Dr Abha Maheshwari, senior lecturer at the University of Aberdeen at the British Science Festival at the university.