No. 380-Investigation and Management of Prenatally Identified Microcephaly



      To update Canadian maternity care and reproductive health care providers on the diagnostic criteria of fetal microcephaly and provide information on the relevant investigations, prognosis, and pre- and perinatal management of this prenatal finding.

      Intended users

      All maternity care (most responsible health provider [MRHP]) and pediatric providers; genetic counsellors; maternity nurses; nurse practitioners; provincial maternity care administrators; medical students; postgraduate residents, and fellows.


      To provide better counselling and appropriate clinical management to women and families who have received a prenatal diagnosis of fetal microcephaly.


      Published literature was retrieved through searches of PubMed or Medline, CINAHL, and The Cochrane Library in 2018, using appropriate key words (prenatal ultrasound, prenatal imaging, fetal, antenatal, or prenatal microcephaly). Additional publications were identified from the bibliographies of these articles.

      Search period

      Seven years (2010-2018); completed final search April 19, 2018. The primary author completed validation of the articles.

      Benefits, harms, and costs

      This document educates readers about (1) the diagnostic criteria for fetal microcephaly, (2) its potential etiologies, (3) investigation and management options both pre- and postnatally. It proposes an evidence-based approach to the diagnosis and management of prenatally detected microcephaly. These recommendations are based on expert opinion and have not been subjected to a health economics assessment. Local or provincial implementation will be required. The authors recognize that there is variability across Canada in access to the cited services and resources. As such, these recommendations were developed in an attempt to promote access and to provide guidance for all provinces and territories across the country.


      The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care.


      • 1
        When fetal microcephaly is suspected, timely referral to a tertiary ultrasound unit should be undertaken for further assessment and to optimize clinical management options (II-2A).
      • 2
        When fetal microcephaly is confirmed by measurement of a head circumference less than or equal to 3 standard deviations below the mean, a thorough and detailed fetal anatomic survey should be undertaken, with focus on cerebral findings and extracerebral signs associated with congenital infection, potential teratogenic exposures, as well as possible chromosomal anomalies or monogenic conditions (II-2A).
      • 3
        When fetal microcephaly is identified, the pregnant woman should be offered a timely consultation with a maternal-fetal medicine specialist and a medical genetics specialist, ideally within a multidisciplinary setting (III-A).
      • 4
        Evaluation of the pregnancy presenting with fetal microcephaly should include:
        • a
          Maternal health assessment and inquiries about maternal conditions associated with poor fetal cerebral growth (for example, phenylketonuria) (II-2A)
        • b
          Detailed review of potential teratogenic and environmental exposures (II-2A)
        • c
          Detailed family history and evaluation of parental head size (III-A)
        • d
          Evaluation of potential infectious causes (II-2A)
        • e
          Discussion of potential additional investigations such as chromosome or single gene analyses, when clinically indicated (III-B)
      • 5
        Once fetal microcephaly is identified by ultrasound, fetal magnetic resonance imaging, when available and if potential findings are likely to alter pregnancy management, may be considered. Fetal magnetic resonance imaging images should be reviewed by a radiologist with expertise in fetal magnetic resonance imaging (III-A).
      • 6
        In ongoing pregnancies with fetal microcephaly, ultrasound examination should be repeated periodically to assess the evolution of the microcephaly and attempt to detect other anomalies not previously identified, as this may influence the counselling as well as the obstetrical or perinatal management (II-2B).
      • 7
        A comprehensive newborn assessment is essential for diagnosis and counselling on the etiology, prognosis, and recurrence risk for future pregnancies, especially when the etiology has not been clearly identified prenatally (III-A).
      • 8
        In cases of termination of pregnancy, stillbirth, or neonatal death, the most responsible health provider should encourage the performance of a complete autopsy by a perinatal or pediatric pathologist to provide maximum information on the diagnosis and etiology of the microcephaly. When a complete autopsy is declined, the performance of at least a partial or external autopsy (including photographs and postnatal magnetic resonance imaging, when available) should be offered (III-A).
      • 9
        Depending on the underlying etiology or in the absence of an identified underlying diagnosis in a previous affected pregnancy, tertiary care ultrasound referral for assessment of fetal head growth for future pregnancies should be considered (III-A).

      Key Words


      CMV (cytomegalovirus), HC (head circumference), MRI (magnetic resonance imaging), SD (standard deviation)
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