medwireNews: Small-for-gestational age (SGA) children should undergo regular measurements for the first 2 years after birth to help identify individuals who will benefit from recombinant human growth hormone (rhGH) therapy, German researchers advise.
And children who are born preterm and SGA would benefit from extending this strategy to the first 5 years of life, recommend Roland Pfäffle (University of Leipzig, Germany) and co-authors in The Journal of Clinical Endocrinology & Metabolism.
“For making an appropriate decision, whether to institute rhGH therapy in SGA patients, one seems to be left with a limited ‘time window of opportunity’”, they emphasize.
“A late decision will impair treatment outcome, as both the age at treatment start and treatment duration have been shown to be the most important factors influencing treatment efficacy.”
The team collated information from the CrescNet auxological database and the Life Child Cohort for 5689 patients attending clinics between 1980 and 2012 for whom final or near-final height (nfh) were recorded on average around age 16 years.
Overall, 9.2% of children were born preterm (64.4% girls) and 90.8% of children were born at term (68.7% girls).
The team found that preterm infants had “slightly” smaller birth length than term infants (–0.38 vs –0.3 standard deviation score [SDS]) and there was a significant difference between the groups at both 1 year (–0.25 vs –0.06 SDS) and at nfh (average –0.61 vs –0.18 SDS).
Mid-parental height also significantly differed between preterm and term infants (–0.46 vs –0.25 SDS) but multiple regression analysis showed that the significant relationship between preterm birth and nfh SDS “was still considerable” after taking into account mid-parental height, the researchers say.
Further analysis showed that while appropriate-for-gestational age (AGA; n=3645) infants had growth “close to the standard mean” at birth and nfh, children born SGA (n=1204) had a “different growth pattern”.
In particular, the catch-up growth (CUG) in the first year and later achieved a significantly lower mean nfh than in their AGA peers (–1.06 vs –0.15 SDS). And although SGA children had a significantly lower average mid-parental height than AGA children (–0.71 vs –0.25 SDS), the main factor appeared to be the degree of growth retardation at birth, explain Pfäffle et al.
To investigate further, SGA children were divided into those with successful CUG, resulting in an nfh of at least the 10th percentile (SGA-CU) and those without CUG and a lower nfh percentile (SGA-S).
SGA-S children had a significantly lower average birth length and weight than their SGA-CU peers regardless of gestational age and sex.
The “strong” CUG in the first year of the SGA-CU versus the SGA-S children, regardless of sex or preterm status, resulted in a 1-year length SDS difference of –0.42 versus –1.35.
Although the researchers had expected a higher average nfh in the SGA-CU versus SGA-S cohort, they say “the difference of 2.14 SDS was surprisingly high” and that, while statistically significant, the average mid-parental height difference of –1.19 SDS explained “only part of this difference”.
When examining individual growth curves, the investigators identified “significant deviations” in height linearity among SGA infants compared with AGA infants.
SGA-S children had a “less pronounced” CUG in the first year followed by a period of catch-down growth until age 6 years in girls and 8–9 years in boys, before another CUG peak and a further catch-down growth period, they explain.
“The most important difference might be, that there is a continued CUG in the 2nd year in all SGA-CU children (term and preterm), which was not seen in the SGA-S term children”, Pfäffle and co-authors write.
Of note, preterm SGA-S children had a late peak in CUG around 2–3 years, and a second period of CUG around 10 years in girls and 12 years for boys.
“Individual growth standards for term and preterm SGA children have been postulated, however, for everyday practice they seem not feasible”, the researchers observe.
“Therefore, repetitive measurements and analyses are mandatory for all SGA children up to 2 years, but for preterm SGA infants up to an age of 5 years.”
By Lynda Williams
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