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Gender differences in cognitive abilities at 2 years in ELBW infants. Extremely low birth weight
G J Hindmarsh1, M J O'Callaghan, H A Mohay
1Mater Misericordiae Children's Hospital, South Brisbane, 4101, Queensland, Australia.
Insights
Female extremely low birth weight (ELBW) infants show cognitive advantages over males at 2 years corrected age. These gender differences in cognitive abilities are similar to those seen in term infants.
Area of Science:
- Developmental psychology
- Neonatal neuroscience
- Pediatric neurology
Background:
- Cognitive gender differences are established in term-born children.
- Uncertainty exists regarding cognitive gender disparities in very preterm infants, especially concerning perinatal brain injury.
Purpose of the Study:
- To investigate gender differences in cognitive abilities at 2 years corrected age among extremely low birth weight (ELBW) infants.
- To assess the influence of perinatal risk and neurological impairment on these gender differences.
Main Methods:
- A cohort of 336 ELBW infants was assessed at 2 years corrected age.
- Infants were categorized by perinatal risk. Cognitive outcomes were measured using the Griffiths General Quotient (GQ) and its subscales.
- A subgroup of 33 neurologically impaired infants was analyzed separately.
Main Results:
- Female ELBW infants scored 4.1 GQ points higher than males.
- Excluding neurologically impaired infants, the female advantage was 3.2 GQ points.
- The primary driver was superior female performance in hearing and speech subscales (6.0 points difference).
- These differences were largely independent of perinatal risk status.
Conclusions:
- Cognitive gender differences in ELBW infants resemble those in term infants.
- These findings suggest gender differences are unlikely to significantly bias general outcome studies for ELBW infants.
- Caution is advised when interpreting studies focusing on specific cognitive domains like language.
Abstract:
Gender differences in cognitive abilities exist for children born at term. For very preterm infants uncertainty exists regarding the presence and extent of such differences and their relationship to perinatal brain injury and neurological impairment. This study examined gender differences in cognitive abilities in a cohort of 336 extremely low birth weight (ELBW) infants at 2 years corrected age. Infants were classified as at low or high perinatal risk at birth according to four perinatal risk factors. A subgroup of 33 neurologically impaired infants was identified. Outcome at 2 years was measured by the overall General Quotient (GQ) on the Griffiths scale and its five subscale scores. Female ELBW children were superior to male ELBW children by 4.1 GQ points (95% CI 1.0, 7.1). If the impaired subgroup was excluded, the difference in GQ was 3.2 points (95% CI 0.4, 5.6), and this difference was predominantly due to female infants being superior in the hearing and speech subscale (6.0 points, 95% CI 2.6, 9.5). These differences were relatively independent of perinatal risk status. Gender differences in the Griffiths GQ for ELBW infants are similar to expected differences for term infants and are unlikely to cause substantial bias in interpreting outcome studies for ELBW infants, unless these involve tests of specific cognitive abilities such as language.