The Atkins diet could reduce a woman's chances of becoming pregnant, research published yesterday indicates.

The Atkins diet could reduce a woman's chances of becoming pregnant, research published yesterday indicates.

High-protein diets such as that advocated by the Atkins regime are linked to increased rates of pregnancy failure in the early stages of conception, scientists have found.

Women who are trying to become pregnant should not adopt protein-rich diets, the experts warned.

More than three million people in Britain are either on or have tried the low-carbohydrate, high-protein Atkins diet over the past few years.

The latest research was presented at the annual meeting of the European Society for Human Reproduction and Embryology (ESHRE) in Berlin yesterday.

Scientists from the Colorado Centre for Reproductive Medicine in the United States fed mice on a diet made up of 25 per cent protein and compared them with mice on a normal diet. Both sets of rodents were then impregnated. The mice on increased protein were found to have a fourfold increase in levels of the chemical ammonium in their reproductive tracts. Ammonium has been linked to problems in mice embryos, such as delayed development and genetic defects.

The embryos from the high-protein mice had fewer cell numbers and a higher rate of cell death, at a crucial stage in embryonic development, just before the embryo attaches to the inside of the womb. Without implantation, pregnancy cannot occur.

The early-stage embryos from both sets of mice were implanted into a third group who had been fed a normal-protein diet. Only 65 per cent of those taken from high protein mice developed into a foetus. Embryos from mice on the lower protein diet had an 81 per cent success rate.

Atkins followers are told to minimise their carbohydrate intake but can eat unlimited amounts of protein, such as meat. While the mice were fed a 25 per cent protein diet, Atkins adherents tend to eat 35 per cent protein during the first induction and weight loss stages of the diet, and are then recommended to remain at 25 per cent for the "maintenance" phase.

The lead researcher, Dr David Gardner, said: "It is conceivable that people who have protein intakes greater than 30 per cent may have problems conceiving. These findings mean that it would be prudent to advise couples who are trying to conceive, either naturally or through [fertility treatment], to ensure that the woman's protein intake is less than 20 per cent of their total energy consumption. The available data certainly indicate that a high protein diet is not advisable while trying to conceive."

Dr Stuart Trager, medical director of Atkins Nutritionals, said: "There was no mention of carbohydrate control in the research conducted by Dr Gardner. The study subjects were mice, which are herbivores. Whether or not these findings or effects would apply to humans is unknown."