Urgent attention: All staff who undertake sonography and early pregnancy scans

Addendum to GTG No 25 (Oct 2006): The Management of Early Pregnancy Loss


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.