BPSU study - Severe microcephaly (SSM-UKI)

Surveillance of severe microcephaly in the UK and Ireland commenced in October 2017. This study will find out how many UK babies are born with microcephaly each year and how seriously this affects their health and developmental outcomes, including problems with hearing and vision. It will provide a better picture of the care and support these babies and their families currently receive.

Lead Investigator

Dr Rachel Knowles
Life Course Epidemiology and Biostatistics
UCL Great Ormond Street Institute of Child Health
30 Guildford Street
London WC1N 1EH
Email: rachel.knowles6@nhs.net

About the study


Microcephaly describes a baby with a ‘small head’, who has experienced poor head growth before or after birth. Severe microcephaly is defined by the World Health Organization (WHO) as a head circumference more than three standard deviations below the mean for age and sex. This rare condition may be associated with abnormal brain structure or neurodevelopment, and with disability, although some babies will develop normally.

Many different causes of microcephaly have been described, including genetic disorders, exposure during pregnancy to environmental toxins, certain drugs, infection or malnutrition. Two important infections in the mother that may cause microcephaly are rubella (German measles) and Zika virus.

You can download the protocol card, including references, below.

Case definition

Any born child aged up to and including 12 months of age who:

  • has been diagnosed with microcephaly in the past month and / or 
  • is noted to have a head circumference that is:
    • more than three standard deviations below the mean for gestational age and sex, or below the 0.4th percentile for age and sex.*

*Use your standard growth chart.

Excluding: Please do not report babies with anencephaly.

Reporting instructions

Please report any child seen in the UK or Republic of Ireland in the last month who meets the case definition.


October 2017 to October 2018 (13 months of surveillance). Follow-up until October 2020 (2 year follow-up).


The study is funded by Great Ormond Street Hospital Children’s Charity.


The study has been approved by East of Scotland Research Ethics Committee (reference: 17/ES/088); HRA Confidentiality Advisory Group (reference: 17/CAG/0126); and the Scottish Public Benefit and Privacy Panel (reference: 1718/0184).

Support group

  • Sense - a national service-providing organisation for children and adults with sensory impairments
  • Contact - a charity supporting families of children living with a disability.