Bruising in Infants Who Are Not Yet Mobile

Bruising is uncommon in infants who are not yet cruising or walking. A study of 973 children at well-child visits, in which abuse was not suspected, found bruising in only 0.6% of infants under 6 months and 2.2% of pre-cruising infants, compared with 17.8% of cruisers and 51.9% of walkers (Sugar 1999). The authors concluded that a bruise in an infant younger than 9 months who has not yet begun moving independently should prompt consideration of abuse or an underlying medical condition.

In the Sugar sample, the most frequent bruise sites were the anterior shin and knee, and forehead bruises were common among walking children. Bruises on the hands or buttocks were not observed at any age (Sugar 1999).

Researchers have also studied prior injuries in the histories of infants later evaluated for abuse. In a case-control study of 401 infants under 12 months evaluated for possible abuse, 27.5% of infants determined to have been abused had a prior "sentinel injury": a previous injury suspicious because the infant could not yet cruise or the explanation offered did not fit. That compares with 8% of infants in an intermediate-concern group and none of 101 infants cleared of abuse (Sheets 2013). Sentinel injuries were bruises in 80% of cases and oral injuries in 11%. Most occurred before 3 months of age, and a medical provider had reportedly been aware of the injury in 41.9% of cases. A later review by one of the same researchers reinforced that an unexplained bruise, oral injury, or musculoskeletal injury in a pre-cruising infant warrants evaluation for occult injury and predisposing medical conditions, along with a report to child-protection authorities (Petska 2014).

That combined evaluation has measurable yield. In a 20-site study of 146 infants under 6 months referred to child-abuse teams for an apparently isolated bruise, skeletal survey found an additional injury in 23.3% of cases and neuroimaging found one in 27.4%; half the infants had at least one additional serious injury. Bleeding-disorder testing, performed in 70.5% of these infants, identified no bleeding disorder in this cohort (Harper 2014).

Bruise location has also been studied as a way to help distinguish abuse from accidental injury. A pilot study of trauma admissions derived the TEN-4 rule: bruising on the torso, ear, or neck in a child 4 or younger, or any bruising in an infant under 4 months, which was 97% sensitive and 84% specific for abuse in that severely injured population (Pierce 2010). A prospective validation across five hospital emergency departments, involving 2,161 children under 4 with bruising, refined this into the TEN-4-FACESp rule, adding the frenulum, jaw angle, cheek, eyelid, and subconjunctiva, plus any bruising in an infant 4.99 months or younger, or patterned bruising. The refined rule was 95.6% sensitive and 87.1% specific against an expert-panel reference standard. The same study noted that bruising caused by abuse is the most common antecedent injury to be overlooked or misdiagnosed as nonabusive before an abuse-related fatality or near-fatality in a young child (Pierce 2021).

What this does and does not mean

A bruise in a pre-mobile infant, by itself, does not establish that abuse occurred. TEN-4-FACESp is a screening tool. A positive result signals a pattern that warrants further medical evaluation rather than a diagnosis. Roughly one in eight children without abuse who have bruising will still screen positive under this rule, so a positive screen calls for additional work-up rather than a conclusion. Several studies drew their samples from infants already referred to child-abuse teams or admitted for trauma, a different population than all bruised infants seen in general practice, and the Sugar study excluded infants where abuse was already suspected rather than formally ruling it out. At the same time, this evidence does not support treating a bruise in a young, non-mobile infant as trivial. The consistent recommendation in the literature is a medical evaluation that considers both inflicted injury and medical mimics such as bleeding disorders, without presuming the outcome either way.

For casework, this evidence is most useful for assessing whether a bruise in a young infant received an appropriate medical work-up, whether mimicking conditions were considered, and whether the reported mechanism fits the infant's developmental stage. It does not substitute for case-specific medical evaluation of the child involved.

The studies cited below are indexed in PubMed; DOI links are provided.

References

1. Sugar NF, Taylor JA, Feldman KW. Bruises in infants and toddlers: those who don't cruise rarely bruise. Arch Pediatr Adolesc Med. 1999;153(4):399-403. doi:10.1001/archpedi.153.4.399
2. Sheets LK, Leach ME, Koszewski IJ, Lessmeier AM, Nugent M, Simpson P. Sentinel injuries in infants evaluated for child physical abuse. Pediatrics. 2013;131(4):701-707. doi:10.1542/peds.2012-2780
3. Petska HW, Sheets LK. Sentinel injuries: subtle findings of physical abuse. Pediatr Clin North Am. 2014;61(5):923-935. doi:10.1016/j.pcl.2014.06.007
4. Harper NS, Feldman KW, Sugar NF, Anderst JD, Lindberg DM. Additional injuries in young infants with concern for abuse and apparently isolated bruises. J Pediatr. 2014;165(2):383-388.e1. doi:10.1016/j.jpeds.2014.04.004
5. Pierce MC, Kaczor K, Aldridge S, O'Flynn J, Lorenz DJ. Bruising characteristics discriminating physical child abuse from accidental trauma. Pediatrics. 2010;125(1):67-74. doi:10.1542/peds.2008-3632
6. Pierce MC, Kaczor K, Lorenz DJ, et al. Validation of a clinical decision rule to predict abuse in young children based on bruising characteristics. JAMA Netw Open. 2021;4(4):e215832. doi:10.1001/jamanetworkopen.2021.5832