From the Research
The posterior fontanel typically closes between 1 to 2 months of age in most infants, as indicated by the study published in 2015 1. This small, triangular soft spot is located at the back of the baby's head where the parietal and occipital bones meet. It's much smaller than the anterior fontanel (the larger soft spot on top of the head) and closes significantly earlier. The closure occurs as the bones of the skull gradually grow and fuse together. This process is part of normal infant development and allows for both brain growth during pregnancy and passage through the birth canal during delivery.
Key Points to Consider
- The timing of fontanel closure can vary somewhat between babies, but if the posterior fontanel appears unusually large or remains open beyond 2 months, it's advisable to consult with a pediatrician to rule out potential issues such as increased intracranial pressure or certain developmental disorders.
- During routine well-baby visits, pediatricians typically check fontanel size and closure as part of normal developmental assessment.
- A study from 2015 1 provides the most relevant information on fontanel closure times, stating that the mean posterior fontanel size was 0.8 cm in newborns and closed in all infants in 2 months of age.
Clinical Implications
- Understanding the normal range of fontanel size and closure time is crucial for early diagnosis of potential disorders.
- The posterior fontanelle can also be used for cranial ultrasound to detect intraventricular hemorrhage in neonates, as shown in a study from 1994 2.
- However, the most recent and relevant study for determining posterior fontanel closure time is from 2015 1, which should be prioritized in clinical decision-making.