Outcomes of fetuses with small head circumference on second-trimester ultrasonography

Prenat Diagn. 2012 Sep;32(9):869-74. doi: 10.1002/pd.3923. Epub 2012 Jun 13.


Objective: We examined the outcomes of pregnancies in which the fetal head circumference (HC) was below the 5(th) centile at the routine second-trimester scan.

Materials and methods: We retrospectively analysed outcomes of 18,377 women according to HC Z scores at second-trimester ultrasound examination between 2001 and 2008. We collected all major malformations, intrauterine deaths and other abnormal outcomes.

Results: Six hundred seventy-four fetuses (3.7%) had an HC below the 5(th) centile. Twenty-one major malformations were noted, consisting mainly of neurological abnormalities (3.1%). There were seven intra uterine fetal death (1.3%). Of all the fetuses, 26% were lost to follow-up. Outcome and neurological development was normal in 467 cases, based on neonatal examination and/or parent or general practitioner reports. Major abnormalities were noted in respectively 26.2%, 3.0% and 1.1% of fetuses with Z scores < -2.5, -2.5 to -2.0, and -2 to -1.645, compared with 0.3% of fetuses with normal HC (p < 10(-4)).

Conclusion: A head circumference below the 5(th) centile at second-trimester scan is associated with various abnormalities, especially neurological disorders. The outcome was worse when the HC was smaller. An HC Z score below -2.5 was strongly associated with neurological and chromosomal abnormalities. Conversely, an HC Z score below -1.645 but above -2, excluding cases with prenatally diagnosed malformations, seems to be reassuring for favorable neonatal outcome.

MeSH terms

  • Female
  • Fetal Growth Retardation / diagnostic imaging*
  • Fetal Growth Retardation / epidemiology
  • Fetus / anatomy & histology
  • Gestational Age
  • Head / anatomy & histology
  • Head / diagnostic imaging*
  • Head / embryology
  • Humans
  • Infant, Newborn
  • Infant, Small for Gestational Age
  • Nervous System Malformations / diagnostic imaging
  • Nervous System Malformations / embryology
  • Nervous System Malformations / epidemiology
  • Pregnancy
  • Pregnancy Complications / diagnostic imaging
  • Pregnancy Complications / epidemiology
  • Pregnancy Outcome / epidemiology*
  • Pregnancy Trimester, Second*
  • Research Design
  • Retrospective Studies
  • Software Design
  • Ultrasonography, Prenatal* / statistics & numerical data