Recent research suggests that given inter-observer variability in ultrasound measurements
and the greater variation in early embryonic growth than has hitherto been assumed, a more
conservative approach to the diagnosis of early pregnancy loss is warranted.
The studies from Imperial College London, Queen Mary, University of London and the
Katholieke Universiteit Leuven, Belgium published in the November 2011 issue of
Ultrasound in Obstetrics and Gynaecology concluded that current definitions used to
diagnose miscarriage could lead to an incorrect diagnosis and they call for clearer evidence-
based guidance on detecting miscarriage through ultrasound scans.
Having carefully considered these papers, we recommend adoption of the following interim
guidance with immediate effect:
1. Ultrasound diagnosis of miscarriage should only be considered with a mean
gestation sac diameter >/= 25mm (with no obvious yolk sac), or with a fetal pole with
crown rump length >/=7mm (the latter without evidence of fetal heart activity)
2. A transvaginal ultrasound scan should be performed in all cases
3. Where there is any doubt about the diagnosis and/or a woman requests a repeat
scan, this should be performed at an interval of at least one week from the initial scan
before medical or surgical measures are undertaken for uterine evacuation. No
growth in gestation sac size or CRL is strongly suggestive of a non-viable pregnancy
in the absence of embryonic structures.
These revised values for ‘mean gestation sac diameter’ and ‘crown rump length’ do not imply
that previously used values were wrong, nor that diagnosis of miscarriage in the past has
been unsafe, This interim guidance suggests a more cautious approach is warranted,
pending more definitive data becoming available. It extends the criteria included in the
RCOG Green Top Guideline No 25, which recommended a conservative approach with
mean gestation sac diameter <20mm or fetal CRL <6mm.
Christoph Lees MRCOG on behalf of the RCOG Ultrasound Advisory Group
Kim Hinshaw FRCOG Lead author, Green Top Guideline No. 25
Philip Owen FRCOG Chair, RCOG Guidelines Committee
David Richmond FRCOG RCOG Vice President (Standards)
19th October 2011
The Ultrasound Advisory Group has representation from the Society and College of Radiographers,
International Society of Ultrasound in Obstetrics and Gynecology, British Maternal-Fetal Medicine
Society, British Medical Ultrasound Society and Royal College of Radiologists. This guidance is
endorsed by BMUS, and by the Council of the Society and College of Radiographers.