Research released on Friday the 7th of October 2011 in the U.K. showed that current guidelines for using ultrasounds to determine that a pregnancy has ended may not always be accurate. The four new studies looked at U.K. ultrasound specifications but when the findings were extrapolated to U.S. guidelines the researchers suggested 1 in 23 women diagnosed with miscarriages could still have a viable pregnancy.
Ultrasound is the gold standard used to determine miscarriage. It is assumed to be exceptionally accurate. However, one of the studies which analysed the existence or size of the gestational sac found that the presence or absence of a gestational sac as well as its size were not fool proof indicators of miscarriage.
Researchers followed 1,060 women who complained of light bleeding or pain – both potential signs that a pregnancy is in trouble between 5 and 8 weeks of pregnancy and had an initial ultrasound scan. As is standard practice, they returned 7-10 days later for another scan to measure the sac’s growth. Those who were still pregnant were followed up again between 11 and 14 weeks.
Typically an embryo larger than 6mm without a heart beat or with no detectable increase in the size of the gestational sac between scans is assumed to indicate miscarriage. However, research showed that it was possible that a healthy pregnancy may not grow measurably in the course of a week or so. In fact, 0.5% of the women in the study – or 1 in 183 – still could have been pregnant even though scan guidelines would have classified their pregnancies as ended.
In the U.K. ultrasounds that reveal an empty gestational sac over 20mm in size result in a diagnosis of miscarriage. In the U.S. the standards set by the American College of Radiology is 16mm. Based on the researchers findings, 8 in 183 U.S. women – or 1 in 23 – would have a miscarriage diagnosed incorrectly.