Fertility experts are appealing for a U-turn in the current rules against multiple embryo IVF implantations, after a new study has revealed that two embryos are better than one – especially for older women trying to conceive.

According to researchers from the Medical Research Council in Bristol and the University of Glasgow, two embryos are better than a single embryo when increasing the chances of a successful pregnancy and live birth, despite previous claims that multiple embryos increase the risk of pregnancy and birth implications.

A spokesperson from the study said: “Greater freedom should be given to clinicians and patients to decide whether to transfer one or two embryos, according to prognostic indicators, such as maternal age.”

The previous belief that the more embryos implanted, the better the chances of conception, resulted in a boost of multiple IVF babies, with 24% of IVF pregnancies resulting in twins or triplets in 2008. Fertility experts became concerned with this statistic, as multiple pregnancies and births as a result of IVF are the single biggest health risk to both mother and child, carrying high risks of premature birth, miscarriage and pre-eclampsia.

As a result, in 2008, the Human Fertilisation and Embryology Authority (HFEA) ordered IVF clinics to reduce the number of multiple births from 24% to 15% by restricting the number of embryos down to one per cycle. The new guidelines paid off, as multiple birth rates lowered to 18% while live birth rates are steadily rising.

However, the new study, published in The Lancet, is appealing for legislations to be relaxed by giving would-be-mothers “greater freedom” when deciding on whether to transform one or two embryos. They came to this conclusion after analysing the outcomes of 124,148 IVF cycles resulting in 33,514 live births.

This is particularly encouraging for older women trying to conceive as it’s been proven that two embryos are more successful in women over the age of 40, as they carry less health risks than in younger women.

"Our findings provide some support for the transfer of two embryos in women older than 40 years, because the risks of pre-term and low birth weight were lower than those in younger women," says a spokesperson from the study.

Meanwhile, the HFEA have spoken out defending their decision to restrict multiple embryos, saying that they didn’t ‘ban’ clinics from doing so, but asked them to select double embryo patients carefully. The full guidelines can be seen on the British Fertility Society’s website.

Medical Director, Dr George Ndukwe, from the Zita West Clinic, added: "Female age is the most important determinant of successful live birth after IVF. Pregnancy rates decline steadily over the age of 35 to less than 5% in women in their 40s.

"I welcome this study because it confirms what we already know – that transferral of two embryos improves chances of success for older women. There’s no justification for the HFEA or any other body to limit the number of embryos transferred in women over 40 to a single embryo in light of this study. Most practitioners are very responsible and should have greater freedom to use their clinical judgement in making decisions in treating their patients," he told The Huffington Post.

However, not all fertility health experts agree that the double embryo appeal will make a drastic difference to older women conceiving via IVF.

“I am an advocate of single embryo transfer because I believe it results in pregnancies that are much lower risk,” fertility expert Emma Cannon told The Huffington Post.

“However, there are always exceptions to the rule and there will be occasions in older women where transferring two embryos is acceptable. But there needs to be special circumstances and I do not believe age is the only indicator. Some women in their 40's perform extremely well and produce good amounts of eggs I see no reason why these women need transfer more than one embryo.

“Other women produce very few of low quality in which case the clinical decision maybe taken to transfer two as the risks of multiple pregnancy would be deemed small. It's important to remember that embryos can always split and one embryo can still become two and two embryos can still become three or even potentially (I have never seen this) four.”

Although the transferal of two embryos is heavily supported in this study, researchers added that three embryos should never be attempted as it massively increases the risk of premature birth. It is currently illegal for a woman over 40 to have more than three embryos into the uterus and over two for women under 40.

Rachel Cutting, Chair of the Association of Clinical Embryologists (ACE) also told The Huffington Post:

"Ensuring the health of both the mother and her baby is our priority and as a result ACE supports the use of single embryo transfer in those patients who are most likely to have multiple births, which is usually those under 37 years old who have good quality embryos.

"That said, it should remain flexible for patients who are less likely to have a multiple birth. It may be suitable to transfer two embryos into patients over 40 years old so as not to compromise their chances of falling pregnant. But any woman having more than one embryo replaced must be fully aware of the health risks involved in a multiple pregnancy.

"We also understand the financial burden for some women of paying for IVF and are calling for more NHS funding for IVF Treatment as we feel that women would be more likely to agree to single embryo transfer if they were able to undergo their treatment on the NHS. It makes financial sense for the NHS to do this because the cost of care for multiple births is far higher than the cost of a cycle of IVF," she explained.

Further to this, the study’s results come after the NHS revealed that it plans to sharply cut funding of IVF cycles, as reported by GP’s magazine, Pulse. The average number of cycles funded each month by primary care trusts so far in 2011/2012 is 14% behind the average rate for the whole of last year, based on Freedom of Information responses collected from 29 trusts.