Postnatal growth of preterm born children ≤ 750g at birth

Background: Extremely low birth weight (ELBW) infants are at risk of impaired postnatal growth. Impaired postnatal growth has been reported to be associated with delayed cognitive and motor development.

Aims: To describe postnatal growth patterns of appropriate and small for gestational age (AGA and SGA) ELBW children in relation to their cognitive and motor outcome at age 5.5.

Study design: Retrospective cohort study.

Subjects: One hundred one children with a BW ≤ 750g, born between 1996 and 2005 in the University Hospital Utrecht, The Netherlands.

Outcome measures: Height (Ht), weight (Wt), occipital-frontal circumference (OFC) at birth, 15 months and 2 years corrected age and 3.5 and 5.5 years. Cognitive and motor outcome at 5.5 years of age, classified as normal (Z-score ≥-1), mildly delayed (-2≤Z-score <-1) or severely delayed (Z-score <-2). AGA (Ht, Wt or OFC at birth ≥-2 SDS) infants were compared with SGA (Ht, Wt or OFC at birth <-2 SDS) infants.

Results: Between birth and 5.5 years catch-up growth in Ht, weight for height (Wt/Ht), Wt and OFC was seen in 72.2%, 55.2%, 28.6% and 68.9% respectively of the SGA infants. For AGA infants we found substantial catch-down growth in Ht (15.4%) and Wt (33.8%). Cognitive and motor outcome was normal in 76.2% and 41.6% of the 101 children. A significantly higher percentage of normal cognitive outcome was found in AGA infants with Wt growth remaining at ≥-2 SDS compared to AGA infants with catch-down growth (83% vs 63%). Next, SGA infants who caught-up in OFC had a higher prevalence of normal cognitive outcome compared to SGA infants who did not catch-up in OFC. Furthermore, a higher percentage of severely delayed motor outcome was found in SGA infants without catch-up growth in Wt compared to SGA infants who caught-up in Wt (61.5% vs 32.2%).

Conclusions: Catch-up growth in Ht, Wt/Ht and OFC occurred in the majority of the SGA infants with a BW ≤ 750 g, but was less common in Wt. AGA children who remained their Wt at ≥-2 SDS have a better cognitive and motor developmental outcome at 5.5 years of age. Catch-up growth in OFC was associated with a better cognitive outcome at 5.5 years of age.