Parents who have had fertility treatment are less sensitive to their children's needs as they approach adolescence than couples who conceive naturally, according to a study.

The findings are part of the first long-term British study of the emotional and social development of children born by egg or sperm donation, known as in vitro fertilisation treatment (IVF). It shows that parents who experience infertility are less sensitive but are seen as more dependable by their offspring.

One in six couples in Britain now need help conceiving. Increasing egg and sperm donation has raised concern that the stress of infertility could lead to "dysfunctional parenting", such as over-protective parents or unrealistic expectations.

But the findings, to be presented by Susan Golombok, director of the Family and Child Psychology Research Centre at City University, at a conference today on children born by assisted reproductive technology (ART), show that these children do not show more emotional or behavioural problems compared with children conceived naturally.

The findings are based on 205 families whose children are now 12 years old. They include 41 IVF families, who had help having their own genetic child; 45 donor insemination families, where donor sperm was used, so the child is not genetically related to the father; 21 egg-donation families, where an egg donor was used, so the child, who, although it was carried by the mother, is not genetically related to her; 55 adoptive families and 43 natural-conception families.

It is the first study to look at these children at the transition to adolescence, when issues of identity become important and when conflict with parents is most likely to occur.

Previous research shows that at 11, adoptive children have more emotional and behavioural problems and take an interest in their biological origins. The present study shows this has not happened yet with ART children, though psychologists are concerned that most have no idea about their genetic origins.

In the study only two of the children conceived using donor sperm and one of the egg-donation children had been told. Many psychologists believe family secrecy is damaging children's development, especially if people outside the family also know.

"When people are undergoing fertility problems they normally confide in their closest friends. In half the families interviewed, someone else other than the parents knew the child was not related to either the mother or the father. As the children are not being told, this could be storing up problems for the future," said Professor Golombok.

The study showed the main reasons parents did not tell their child was concern they would love the non-genetic parent less, and the fact that they did not know when and how to tell the child.

"Most parents felt at the age of 12 it was too late to tell their child but wished they had done it earlier," said Professor Golombok.

Boys born using the latest fertility treatment have three times the risk of genital abnormalities. A study published in the Journal of Human Reproduction tomorrow shows children born using intra-cytoplasmic injection, where a single sperm is injected into the egg, are more prone to abnormalities than children conceived naturally.