London - Mothers who have babies using donated eggs tend not to bond so closely with their children, a study shows.
Research by the University of Cambridge has found women who use egg donors may have slightly different relationships with their babies.
Some admit they struggle with not being biologically related to their child.
These women are warm and loving but show small differences when playing with the child, according to the study of 85 families who used egg donation.
They are less sensitive to their baby’s smile and eye contact, while the child is less likely to involve its mother by holding out or waving toys.
Dr Susan Imrie, who co-authored the study by the University of Cambridge’s Centre for Family Research, will present it this week at the annual meeting of the American Society for Reproductive Medicine in Denver.
"Women who use egg donation have often had a longer route to parenthood," she said. "Our research does show that some women are still finding their feet as egg-donation mothers and that this can be challenging.
"A small number told us not having a genetic link with their child took some time to get their head around."
Egg donation began being used by fertility clinics in the late 1980s but has grown in popularity over the past decade.
Women who donate eggs are usually aged 18 to 35, so their eggs are younger, of better quality and thus far more likely to result in a pregnancy.
For older women whose own eggs may make it difficult or impossible to start a family, this can be the better option. The British researchers interviewed women with children from egg donation, whose partners were the biological fathers, and whose babies were aged between six and 18 months.
They filmed parents playing with their children for ten minutes.
Comparing mothers who used egg donation with 65 women who conceived using their own eggs, there were differences.
Women who used egg donors were less sensitive towards their babies, based on behaviour such as smiling at the child or responding to a baby pointing towards a toy or showing signs of boredom.They were less good at structuring play activities.
Their babies were less responsive, based on eye contact and smiles towards their mother, and involved her less by, for example, waving or holding out toys. The study suggests women may interact with babies born by egg donation differently, and their babies may respond differently as a result. However, during interviews, little difference was found in the women’s feelings towards their children.
Women whose children came from egg donation had less confidence in their parenting skills, but this was thought to be due to the mothers’ age.
The results also showed no difference in hostility or controlling behaviour for women whose babies were born using eggs from another woman.
The study, published in the journal Child Development, states: "Research with egg-donation mothers of older children suggests that mothers may feel more comfortable with non-genetic motherhood over time."
Stuart Lavery, a fertility expert at Imperial College, London, said: "This is an important study that suggests there may be some differences in the quality of the parent-child relationships between egg donation families and conventional IVF families.
"Given the increased use of egg donation and previous studies that were more reassuring, this issue deserves further studies in bigger populations, and probably most importantly over longer time frames."