Current guidelines that help clinicians decide whether a woman has had a miscarriage are inadequate and not reliable, and following them may lead to the inadvertent termination of wanted pregnancies, according to a series of papers published in the international journal, Ultrasound in Obstetrics and Gynaecology.

-Team@CMHF

• This research shows that the current guidance on how to use ultrasound scans to detect a miscarriage may lead to a wrong diagnosis in some cases.
• A miscarriage is often confirmed by using an ultrasound scan to see whether there is any sign of a pregnancy sac or embryo in the womb, and women understandably expect that when a diagnosis of miscarriage is made there is no room for error.
• Four studies based at Imperial College in London indicated multiple concerns about existing guidelines, which are:
1. Existing guidelines for mean gestational sac diameter (MSD) and embryo crown-rump (CRL) length used to determine miscarriage vary from 13 to 22 mm and 3 to 8 mm, respectively. After conducting an observational cross-sectional study and reviewing false-positive diagnoses, the researchers suggested an MSD cut-off of >25 mm and a CRL cut-off of >7 mm to minimize the risk of a false-positive diagnosis of miscarriage.
2. A second study found overlap in MSD growth rates between viable and non-viable intrauterine pregnancies of uncertain viability. When there is doubt about the diagnosis of miscarriage, current guidance suggests the pregnancy sac should be re-measured seven to 10 days later. If the sac does not grow, it is assumed that a miscarriage has occurred. However, the study found that perfectly healthy pregnancies may show no measurable growth over this period of time. No cut-off exists for MSD growth below which a viable pregnancy could be safely excluded, the researchers concluded.
3. A systematic literature review to evaluate the accuracy of first trimester ultrasound in the detection of miscarriage identified a lack of high-quality data to inform guidelines for early pregnancy demise. The researchers called for an appropriately powered, prospective study using current ultrasound technology and an agreed reference for viability or non-viability.
4. The final study revealed variation in the size of gestational sacs of up to 20 percent 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 a physician might incorrectly conclude that no growth had occurred. These errors could lead to a false diagnosis of miscarriage being made in some women.

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