Parents have already had to take the decision to terminate a pregnancy

When terminations happen because of a suspected foetal anomaly, doctors say an autopsy can explain more about the baby's condition.

They can also help estimate the risk of any future pregnancy being affected.

Researchers writing in the British Medical Journal say parents need to be told about the benefits of post mortem examinations.

They appear to feel as if they are doing us a favour by agreeing to have a post mortem - but that isn't the case Dr Gordan Vujanic, University of Wales

They may be offered the option of a termination if the foetus is discovered to have an abnormality such as anencephaly, where the brain is small or missing, or spina bifida.

But a growing number of parents are choosing not to have a post mortem examination after they have terminated such a pregnancy.

Pathologists say the scandals at Alder Hey Children's Hospital and the Bristol Royal Infirmary, which revealed organs were being removed in post mortem examinations and stored without parents' consent, reduced the numbers willing to allow the procedure.

Estimating risk

Researchers from the John Radcliffe Hospital in Oxford identified all pregnancies terminated in the city after prenatal diagnosis between 1991 and 2000.

They looked at the diagnoses and autopsy findings to see how often having an examination carried out by a specialist paediatric pathologist changed the advice given to parents.

Out of 57,258 deliveries, 309 were terminated due to a defect diagnosed before birth.

The number of terminations carried out due to foetal anomalies being discovered increased from 129 between 1991 and 1995 to 180 in 1996-2000.

But the percentage of foetuses that underwent post mortem examinations fell from 84% to 67%.

In 27% of cases where the prenatal diagnosis was by ultrasound scan alone, the autopsy provided information that led to the risk of future pregnancies being affected being re-evaluated.

In 8%, the risk was reassessed as being as high in one in four.

The researchers say by declining the option of a post mortem examination, parents will remain ignorant of information that may have implications for future pregnancies.

'Implications'

For example, ultrasound scans carried out before a termination can indicate a condition called cystic kidneys.

There can be numerous reasons for a foetus to be affected, some of which have a recurrence risk of up to 50%, while others carry a very small risk.

Writing in the BMJ, the researchers from the Women's Centre at the John Radcliffe Hospital led by Dr Patricia Boyd, said: "After termination of pregnancy, most parents will want to know if the prenatal prediction was accurate and what the implications are for future pregnancies.

"Such information may be obtained from the post mortem examination.

"After the adverse publicity surrounding the paediatric pathology autopsies at Alder Hey Hospital there is widespread recognition that parents need a full explanation to make an informed decision.

"This information should not only be about the autopsy technique but also about the potential benefits.

"Currently, there is little quantative information about the likelihood of post mortem being if practical use to parents and families by modifying the assessment of the risk of reoccurrence."

Deterrent

Dr Gordan Vujanic, a consultant pathologist at the Department of Pathology at the University of Wales College of Medicine, told BBC News Online it was important parents understood the potential benefits of post mortem examinations.

But he said the scandals at Alder Hey and Bristol had deterred parents from giving their permission.

He said: "They appear to feel as if they are doing us a favour by agreeing to have a post mortem.

"But that isn't the case. Our reason for wanting to carry out the examination is to help parents and doctors to see if the abnormality is there and if there are other abnormalities not discovered by the ultrasound which might alter the diagnosis."

Professor James Underwood, president of the Royal College of Pathologists, said: "Bearing in mind that medically certified causes of death are significantly wrong or incomplete in up to 30% of cases, autopsies provide the best opportunity for fully and reliably establishing the reasons for death.

"For example, the study from Oxford shows how this can be helpful in guiding decisions about future pregnancies."