A Danish study has found that IVF babies born from embryos that are frozen are less likely to be underweight or premature than those conceived during fresh treatment cycles.
Frozen embryos are thawed before they are used and there has been some concern in the past that the freezing process possibly damages the embryo in some way.
The researchers found that the average birth weight of those babies was 200g more than in fresh-embryo IVF and they say the use of frozen embryos could soon be accepted as a completely safe procedure which can be used even more frequently.
The team led by Anja Pinborg, of the Copenhagen University Hospital, say the findings are important because women are increasingly encouraged to use one fresh embryo in order to avoid multiple births and to freeze any others produced in the process for use later.
Dr. Pinborg says it is highly unlikely that freezing improved the health of embryos and a possible explanation might be that the patients who froze embryos were generally young women with a good prognosis and also that poor quality embryos were more likely to die during the thawing process.
Dr. Pinborg presented the research at the European Society of Human Reproduction and Embryology conference in Barcelona this week and says the findings are reassuring.
Another team of researchers from Yale University also at the conference say that IVF success rates could be improved by as much as 15 per cent with a "viability index" for selecting embryos with the best chance of a healthy pregnancy.
The new "fitness test" can apparently predict which IVF embryos will implant into the womb up to 70 per cent of the time and is a non-invasive procedure done from cultures grown in the laboratory.
The team say the technology, known as metabolomics, should be ready for widespread use within two to three years and could become a routine part of fertility treatment.