The ability to detect congenital anomalies in the fetus has improved significantly over recent years and an ultrasound examination at around 20 weeks of gestation is now a routine part of antenatal care, write Ruth Lester and Mark Kilby.
Part of that Fetal Anomaly Screening Programme (FASP) 18-21 week scan includes assessment of both upper and lower arms and the metacarpals in both hands (PHE, 2018).
After the mention of a possible anomaly, expectant parents will immediately experience worry and uncertainty until the baby is born. This might continue for several more months, before they see paediatric specialists who will be able to provide the parents with a more specific diagnosis and, eventually, a treatment plan.
Although referral to a Fetal Medicine Specialist who has links with relevant paediatric and genetic specialties can be made urgently, there may be further delays for the anxious parents. New guidelines indicate that such referrals should be seen within three working days, however three days can be a long time when waiting.
The fetal medicine assessment is likely to include further detailed ultrasound examinations, and the possibility of using other prenatal imaging techniques such as 3D/4D ultrasound and/or magnetic resonance imaging (Nemec et al, 2011). A potential discussion around the possibility of invasive tests for the exclusion of chromosome or monogenic disease, may also be relevant.
However, the sonographer who initially detects an anomaly has a primary responsibility to give uncertain and worrying information to a parent, at a stressful and emotional time in a mother’s life.
Congenital Upper Limb Anomalies (CULA) are a rare and heterogeneous group, and therefore it is understandably difficult for a sonographer to offer precise information to help relieve the parent’s distress. The RCOG (2010) recommend that: ‘If the scan reveals either a suspected or confirmed abnormality, the woman should be informed by the sonographer at the time of the scan. It is essential that all practitioners performing fetal anomaly ultrasound screening should be trained to communicate abnormal findings to women, as such information is likely to have significant emotional impact.’
In a study from Western Australia with a population of 1.6 million, 1 in 506, or 1.97 per 1,000 live births, were registered with a CULA. Forty-six percent of the babies with a CULA had some other anomaly of which 101 (20%) were syndromic, 48 (9%) had multiple anomalies that were not classifiable into a syndrome, 45 (9%) had a foot anomaly, and 40 (8%) one other anomaly (Giele, 2001).
In a study of 100 children presenting to a congenital hand clinic, the antenatal ultrasound examination picked up 31 cases of CULA. Only 18 of those 31 cases were diagnosed accurately by ultrasound, although 3D ultrasound was found to improve results (Grey et al, 2013). Other data has indicated low overall sensitivity. Detection rates being highest in those fetuses with anomalies involving the entire upper extremity of the limb (Piper et al, 2015).
A few more facts:
- If a single limb is involved, further consultation will be made but some reassurance can be given that their child is likely to live a normal and productive life.
- Just over half of CULA are likely to be bilateral, but with no other identifiable anomalies, these babies will certainly need more investigations, but are more than likely to live a highly successful life.
- Where multiple anomalies are detected, urgent referral is appropriate along with a fuller assessment and it is therefore more difficult to offer reassurance. Increasingly, such fetuses are seen in combined specialist Fetal Medicine / Genetics Clinics and the use of prospective prenatal exome sequencing allows accuracy of genetic diagnosis and an improved definition of overall prognosis (Lord et al, 2019).
So, what can sonographers tell parents at the time of the ultrasound examination, when an upper limb anomaly is detected?
Honesty about uncertainty! Be honest about what you know, but also what is unknown at the time of the scan. Give clear instructions about what the next steps are, for example, refer directly to a midwife in the antenatal clinic or whether a fetal medicine referral is being made by the sonographer directly. Provide details of support available, for example the Reach charity is an organisation which supports children and their families with upper limb differences.
Reach trustee Ruth Lester is a former surgeon at Birmingham Children’s Hospital, and Professor Mark Kilby is a clinical scientist and Honorary Consultant in Fetal Medicine at the Birmingham Women's Foundation Trust Hospital.
References
Giele, H, Giele, H. Allison, M.. The Incidence and Epidemiology of Congenital Upper Limb Anomalies: A Total Population Study. J of Hand Surg Am. 2001 Jul;26(4): 628-34
Grey, B. Calee, R, Dicke, J, Steffen, J. Goldfarb, C.. The Utility of Prenatal Ultrasound as a Screening Tool for Upper Extremity Congenital Anomalies. J of Hand Surg Am. 2013, 38 (11):2106-2111
Lord, J. McMullan, D. Eberhardt, R. Rinck, G. et al. Prenatal exome sequencing analysis in fetal structural anomalies detected by ultrasonography (PAGE): a cohort study. The Lancet. 2019 393 (10173): 747-757
Nemec U, Nemec SF, Krakow D, Brugger PC, Malinger G, Graham JM Jr, Rimoin DL, Prayer D. The skeleton and musculature on foetal MRI. Insights Imaging. 2011 Jun;2(3): 309-318
Piper SL, Dicke JM, Wall LB, Shen TS, Goldfarb CA. Prenatal Detection of Upper Limb Differences with Obstetric Ultrasound. J Hand Surg Am. 2015 Jul;40(7): 1310-1317.e3
Public Health England (2018) NHS Fetal Anomaly Screening Programme Handbook. Available at:
https://assets.publishing.service.gov.uk (Accessed 22.3.2021)
RCOG (2010) Termination of Pregnancy for Fetal Abnormality in England, Scotland and Wales. Available at: https://www.rcog.org.uk (Accessed 22.3.2021)