Boys conceived through IVF tend to have short fingers - a trait linked to infertility, say researchers in a study published in the journal of Reproductive Biomedicine Online. The researchers studied children conceived through an IVF method called ICSI (intracytoplasmic sperm injection), where a single sperm is injected into the egg.

The finger lengths of 211 children conceived by ICSI were compared with those of 195 naturally-conceived children, all aged between four and nine years old. The boys in the ICSI group had similar heights to the control group but, after taking height into account, the researchers found they had significantly shorter fingers.

While the boys were too young to test fertility directly, 'perturbations in finger length in ICSI children may be inherited from their fathers and, in the case of boys, could be associated with lower fertility and reduced sexual attractiveness', according to the journal paper.

The study was led by Dr Alastair Sutcliffe, a paediatrician at the Institute of Child Health in collaboration with Southampton University and researchers in Germany.

'This is the first study of this kind on these children', he told the Telegraph.

'We don't yet know the implication of the findings because the children are very young, but we need to inform people [about the possible risks of the ICSI procedure]'.

Finger length may be partially determined in the 14th week of pregnancy and is linked to levels of testosterone exposure which is, in turn, controlled by genes. But more research is needed to validate the findings, according to NHS analysis of the research, due to the small sample size and the need to test fertility directly in post-pubertal boys conceived by ICSI.

ICSI is a procedure used to overcome male fertility problems, such as a low sperm count or where the sperm are lazy (immotile). Almost one in 50 babies born in Britain is conceived artificially and nearly half the couples having treatment undergo ICSI. The first ICSI baby was born in 1992 and now there are around 3,700 births a year from this procedure, according to the Daily Mail.

Allan Pacey, a senior expert in male infertility at Sheffield University and a spokesman for the British Fertility Society, told the Telegraph that ICSI should be used 'only when absolutely necessary'.