In their study, researchers in Denmark found that babies born after a frozen embryo was thawed and implanted had higher birth weights and were unlikely to suffer abnormalities as compared to those born from fresh embryos.

"Only the very top quality embryos survive the freezing and thawing process. And you only get pregnancies in patients with lots of good embryos to freeze," lead researcher Dr Anja Pinborg was quoted by 'The Daily Telegraph' as saying.

The researchers at Copenhagen University came to the conclusion after comparing over 1,200 children who were born from frozen embryos between 1995 and 2006 to 17,857 infants who had been born from fresh embryos during that period.

Freezing embryos allows couples to have several in-vitro fertilisation (IVF) treatment cycles from the same egg collection, reducing the number of times that the ovaries are stimulated.

The eggs are placed in the womb three to five days after ovulation in exactly the same way as fresh embryos.

Multiple births accounted for 27.3 per cent of children born from fresh embryos, compared with 14.2 per cent when frozen embryos were used.

Babies from frozen embryos were on average 200 grams heavier on birth than those from fresh embryos; and proportion of low birth weight and pre-term FER children was also lower, the study found.

"Most encouragingly, we found no increased risk of congenital malformations in the FER group; the rate in this group was 7.1 per cent compared to 8.8 per cent where fresh embryos had been used.