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.
Currently 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.
But the new results suggest it might be wise to freeze all embryos.
Boost your chances of success during pregnancy by eating well...
Superfoods For Pregnancy
Superfoods For Pregnancy(01 of12)
Open Image Modal (credit:Alamy)
Tofu Smoothie(02 of12)
Open Image ModalBenefit To Baby: Healthy GrowthProtein is needed to build and repair cells, and is essential to a baby's development and growth. Red meat and dairy are rich in protein, but they're also high in saturated fats. Balance your diet with fish protein (in all fish products), which also contains essential fatty acids. And don't forget vegetable protein, which includes brown rice, quinoa, chickpeas, lentils, baked beans, pumpkin seeds and cashew nuts.A great alternative protein source, tofu is low in fat and will help balance those blood sugar levels. Add to juice from pomegranate and mixed berries for a sweet drink that also packs a powerful antioxidant punch. (credit:Alamy)
Sunflower Seeds(03 of12)
Open Image ModalBenefit For Mother And Baby: Boost Energy Levels And Provides Nutrition To BabyIron is vital for your baby's physical growth and brain development, and helps produce the blood required to supply nutrition to the placenta.Not enough iron, and you can feel tired and be more susceptible to infections. There's also a greater risk of premature birth and your baby having a low birth weight. (credit:Alamy)
Eggs(04 of12)
Open Image ModalBenefit To Baby: Brain DevelopmentVitamin B6, also known as pyridoxine, helps your body metabolise protein, fats, and carbohydrates. It also helps form new red blood cells, antibodies, and neurotransmitters, and is vital to your baby's developing brain and nervous system. (credit:Alamy)
Pumpkin(05 of12)
Open Image ModalYoghurt And Honey(06 of12)
Open Image ModalBenefit To Mother And Baby: Increases Energy Levels And Bone BuildingHigh in calcium (important during pregnancy for building your baby's bones) with a sweet kick from the honey, this treat should tide you over without making you sleepy.Dairy foods provide vitamins A and D, which are essential for bone-building and bone maintenance for you and your baby. They are also a good source of protein. (credit:Alamy)
Figs(07 of12)
Open Image ModalBenefit to Mother: Eases Heartburn And Water RetentionDried figs are laden with digestive enzymes, which should help you to digest your food and ease those heartburn symptoms. They're also rich in the essential mineral potassium, which helps to maintain the body's fluid balance during pregnancy, which is essential to battling swollen legs, hands and ankles. (credit:Alamy)
Oily Fish(08 of12)
Open Image ModalBenefit To Baby: Maintains Healthy Nervous SystemOmega-3 fatty acids are vital for your baby's brain and nervous system, as well as your own mental health.Foods rich in omega-3 include oily fish like fresh tuna, mackerel and sardines, although restrict your intake to twice a week, as too much fish can increase risk of pollutants.Fatty acids help brain development and work to improve its function, so as well as being nutritious, slow-releasing energy snacks, like sesame seeds, which help keep you mentally alert and working well throughout the day. (credit:Alamy)
Ginger(09 of12)
Open Image ModalBenefit To Mother: Alleviates Morning SicknessGinger has long been associated with alleviating nausea and has been used as a medicine in Asian, Indian, and Arabic herbal traditions since ancient times. In China, for example, ginger has been used to help digestion and treat stomach upset, diarrhea, and nausea for more than 2,000 years.Ginger biscuits are a good food to nibble on when the nausea starts, or sip on ginger tea or suck on ginger flavoured sweets. Peppermint and mint are also great nausea-relieving agents too. (credit:Alamy)
Sweet Potato(10 of12)
Open Image ModalBenefit To Baby: Strengthens BonesSweet potatoes offer a rich source of folic acid, which helps prevent neural tube defects in foetuses. It also protects your unborn baby from spinal cord problems, such as spina bifida. lentils are also a great for increasing your folic acid intake, as one cup provides 358mcg of folic acid, almost the daily requirement of 400mcg.Fruits like strawberries are a great way to get your folic acid, and even tastier if you dip them in chocolate!Scientists in Finland found that eating chocolate when pregnant resulted in happier, livelier babies, but keep your waistline in mind and be conservative when dipping. (credit:Alamy)
Almonds And Apricots(11 of12)
Open Image ModalBenefit To Mother: Curbs Food CravingsA handful of almonds and apricots will provide you with a sweet kick that's high in protein - this will help to curb cravings as well as keeping you feeling fuller for longer. (credit:Alamy)
Parsnips(12 of12)
Open Image ModalBenefit To Mother: Protects From Pre-eclampsiaParsnips are a good source of fibre and folate (the natural form of folic acid), as well as providing potassium (associated with a lowering in blood pressure) which is vital for protecting against pre-eclampsia, a condition caused by high blood pressure. (credit:Alamy)
Dr Abha Maheshwari, senior lecturer at the University of Aberdeen and Consultant in Reproductive Medicine with NHS Grampian, said: "We found pregnancies arising from the transfer of frozen thawed embryos seem to have better outcomes both for mums and babies when compared to those after fresh embryo transfer.
"If pregnancy rates are equal and outcome in pregnancies are better, our results question whether one should consider freezing all embryos and transfer them at a later date rather than transferring fresh embryos. This represents a major paradigm change in assisted reproduction, and one which could satisfy the twin demands of optimising safety and success."
Dr Maheshwari presented her findings at the British Science Festival, which opened today at the University of Aberdeen. The research also appears in the journal Fertility Sterility.
The scientists think there could be two reasons for the results. One is that only prime quality embryos are likely to survive the freezing process. The other, more popular, theory is that the womb lining is allowed time to settle down and recover from the rigours of IVF hormone treatment.
A pregnancy too soon after a women is given fertility-boosting drugs is known to increase the risk of hyperstimulation.
Dr Maheshwari added: "The existing data do have a number of limitations which need to be addressed in the context of further research before this strategy should be rolled out into routine clinical practice.
"The initial step must be to provide robust evidence to demonstrate that elective freezing of embryos can increase the chances of having a healthy baby, which would be best performed in the context of a large randomised controlled trial.
"In the meantime my advice to women undergoing IVF is that there is no reason, yet, to change the way they approach IVF.
However, there should be no concerns about freezing embryos and resulting pregnancies, if your clinic is offering the freezing of spare embryos."
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Open Image ModalAllan Pacey, senior lecturer in reproduction and developmental medicine at the University of Sheffield, said: "I think this is interesting because some people are nervous about frozen embryos, and there have been various headlines about this study or that which suggest that frozen embryos may be a worry.
"What's really useful is that it shows that from the point of view of the woman's health during labour, and some early measures of the baby's health, frozen embryos do all right and are arguably better.
"I'd have to sound a cautious note about suggesting that all IVF embryos should be frozen, because the study doesn't support that. It only looked at successful frozen cycles. What it does do is give support to the idea that transferring one fresh embryo and freezing the others is okay.
"Freezing all embryos would have a catastrophic effect on pregnancy rates."