They told the parents of a seven-year-old girl conceived after the father had a vasectomy that they could not pursue a medical negligence claim for the expense of bringing her up.
George McFarlane, 48, and his wife Laura, 44, from Arbroath, Scotland, had lodged a pounds 100,000 claim against the Tayside health board, claiming that doctors had negligently advised them that the vasectomy had been successful.
But in a landmark ruling the law lords blocked their claim, ruling out any similar actions in future in Scotland or England and Wales. Twenty couples involved in similar cases were thought to be awaiting the ruling.
Giving judgment, Lord Millett said: "In my opinion, the law must take the birth of a normal, healthy baby to be a blessing, not a detriment. In truth, it is a mixed blessing. It brings joy and sorrow, blessing and responsibility." He added: "It is morally offensive to regard a normal, healthy baby as more trouble and expense than it is worth."
The McFarlanes did not go away entirely empty-handed. The lords allowed Mrs McFarlane to claim up to pounds 10,000 for her own personal pain, distress and loss resulting from the unwanted pregnancy.
The couple's case had been rejected by the Court of Session in Edinburgh. That judgment was overturned at appeal, when Lord McClusky said: "To treat parenthood as a wholly unblemished blessing is to ignore the realities of experience."
The law lords yesterday allowed an appeal by the health board and held that the birth of a healthy, though unwanted, baby could not form the basis of a compensation claim for the cost of raising the child.Reuse content