Healthy babies lost due to false miscarriage diagnosis

Hundreds of wanted pregnancies may be ended each year because miscarriage tests are not as reliable as they should be, doctors have said.

A series of four studies found that the current methods used to determine whether a woman has miscarried could lead to a wrong diagnosis being made.

An estimated one in five pregnancies end in miscarriage. If a woman suffers pain or bleeding early in pregnancy, or has a history of miscarriage, doctors may suggest an ultrasound scan.

Scans look for the presence of the embryo in the pregnancy sac, measure the length of the embryo and sac, and also look for signs of a heartbeat. Doctors may also carry out tests to measure the levels of pregnancy hormones.

If there is doubt about the diagnosis of miscarriage, doctors are advised to re-measure the pregnancy sac seven to ten days later. If the sac does not grow during this time, it is assumed that a miscarriage has occurred. The woman may then choose to terminate the pregnancy.

However, one of the studies, led by Professor Tom Bourne from Imperial College, London, found that perfectly healthy pregnancies may show no measurable growth over this period of time.

Another revealed an up to 20 per cent variation in the size of the pregnancy sacs reported when different clinicians measure the same pregnancies.

If the first measurement over-estimated the sac size and the second measurement some days later underestimated it, then it would be easy to incorrectly conclude that no growth had occurred, and an incorrect diagnosis of miscarriage made.

The current method used to diagnose miscarriage is based on evidence from a few studies carried out at least 10 years ago involving small numbers of women, one of the studies concluded which are published in the journal Ultrasound in Obstetrics and Gynaecology. The researchers from Queen Mary, University of London, said the results highlighted the need for more 'good quality' research.

Professor Bourne from Imperial College said: "For most women sadly there is nothing we can do to prevent a miscarriage, but we do need to make sure we don't make things worse by intervening unnecessarily in on-going pregnancies.

"Currently there is a risk that some women seeking reassurance with pain or bleeding in early pregnancy may be told they have had a miscarriage, and choose to undergo surgical or medical treatment when the pregnancy is in fact healthy.

"By identifying this problem we hope that guidelines will be reviewed so that inadvertent termination of wanted pregnancies cannot happen.

"We hope our work means that the guidelines to define miscarriage are made as watertight as we would expect for defining death at any other stage of life."

This article was published on Fri 14 October 2011