"Not necessarily everyone who does the scans is really very experienced" ... Professor George Condous.
Misdiagnoses of early miscarriage may be leading doctors to inadvertently terminate healthy pregnancies, ultrasound experts have warned.
Many women who have a miscarriage then have a curette, a medical procedure to remove the pregnancy remains. But emerging research indicates that one in 200 pregnancies thought to have miscarried may actually have been viable.
Associate professor at the University of Sydney, George Condous, said more conservative guidelines might be needed to ensure women are not effectively aborting a foetus by mistake.
"We were potentially terminating pregnancies that were wanted," said Professor Condous, who is also the director of Omni Ultrasound, a specialist gynaecological and obstetrics clinic.
The issue is dividing the medical community, with the Royal Australian and New Zealand College of Obstetricians and Gynaecologists denying there is a problem of women being wrongly diagnosed as having had an early miscarriage.
First-trimester miscarriage is diagnosed using ultrasound measurements of the foetal sac, embryo size and whether a foetal heartbeat can be seen.
In a letter published in the Australian and New Zealand Journal of Obstetrics and Gynaecology this month, Professor Condous warned that individual clinicians could vary in the measurements they took, leaving them to make mistaken judgments about whether the foetus was developed properly.
"Not necessarily everyone who does the scans is really very experienced," he said.
He is seeking ethical approval for a study to see if the guidelines for the size of the foetal sac should be increased again from the currently used 25mm to 30mm, and for the embryo from 7mm to 10mm.
The even smaller measurements used before the guidelines were changed in November last year (20mm and 6mm) were linked to wrongly diagnosed miscarriage for one in every 200 pregnancies of uncertain viability, according to UK research.
About a quarter of all pregnancies end in miscarriage, and Professor Condous said it was just as devastating for a woman to lose her baby in early pregnancy. "The medical community underplays early losses, and we need to be treating them with the same rigour," he said.
Philippa Ramsay, the director of Ultrasound Care, a specialist women's ultrasound practice, said often women, too, did not want to wait for further scans to double-check the miscarriage diagnosis, particularly during the holiday period.
"It's a typical issue we deal with, we have a lot of people who want a really early diagnosis," she said. "Ultrasound is a little window that shows you what's going on in there, so everyone has high expectations."
Dr Ramsay said there could be "huge" differences in the way clinicians read ultrasounds. "The skill of the operator really varies between practices that concentrate entirely on obstetrics and practices where they scan all sorts of body parts," she said.
Before ultrasound, women just waited to see what happened. "But now we are trying to give them a diagnosis before their body has miscarried," she said. "It's a bit tricky."
Dr Ramsay said Australian ultrasounds are usually assessed by two qualified practitioners, unlike in the UK, although she still often advised women to wait for a second scan before having a curette.
But the president of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, Michael Permezel, said it would be wrong to alarm women or make them think their miscarriage could have been wrongly diagnosed.
"It's certainly very wrong for them to be alarmed that under the new criteria there would be any risk at all [of false diagnosis]," he said.
He denied there had been wrongly diagnosed miscarriages in Australia, and said if there had been they would be a "tiny proportion".
How women dealt with miscarriages should be decided on an individual basis. "Some women feel the best thing is for them to get it out of the way and put it behind them, and some women, particularly older women, don't want to wait up to a few weeks for the miscarriage," he said.
What is looked for
- At five weeks ultrasoundists look at the foetal sac
- At six weeks they look for yolk in the sac
- At seven weeks they look for a foetus and a heart beat