Although it is technically illegal under the 1967 Abortion Act, an abortion based on the sex of a foetus can still be carried out if two doctors agree that it is in the best interests of the woman's health. This is one reason why it has been so difficult to prosecute doctors offering terminations where gender has been an issue.
The former director of public prosecutions, Keir Starmer, articulated the difficulty last October in a letter to the Attorney General Dominic Grieve explaining why he was not going to pursue the prosecution of two doctors allegedly caught offering sex-selective abortions in a "sting" organised by The Daily Telegraph.
"The law does not, in terms, expressly prohibit gender-specific abortions; rather it prohibits any abortion carried out without two medical practitioners having formed a view, in good faith, that the health risks of continuing with a pregnancy outweigh those of termination," Mr Starmer said.
"On the facts of these cases, it would not be possible to prove that either doctor authorised an abortion on gender-specific grounds alone…The only grounds for a prosecution would be that although we could not prove these doctors authorised a gender-specific abortion, they did not carry out a sufficiently robust assessment of the risks to the 'patient's' health to enable them to come to an opinion in good faith that the risks to her health continuing with the pregnancy outweighed those of termination," he explained.
The other difficulty is the reluctance of ministers to accept that there is a problem. Following the Daily Telegraph's investigation, the Department of Health analysed birth statistics and the sex ratios of children born in the UK to women born abroad and found no significant gender imbalances.
The health department came to the conclusion that there was no evidence for widespread illegality, with women undergoing pregnancy terminations when they carry female foetuses in order, ultimately, to have sons.
The health minister, Earl Howe, stated categorically last June that the issue had been thoroughly investigated and nothing had been found to suggest that abortions were being carried out on the basis of gender.
"On sex selection, we have no evidence at all of gender-related abortions in the UK. Again, concerns were expressed about this in the press, but analysis has been done that shows that the UK birth ratio is within normal limits," Earl Howe told Parliament.