Growth in the VLBW; could do better!

Among over 300,000 VLBW infants in the Vermont Oxford Network database between 200 and 2013, the weights at discharge were plotted against the Fenton percentiles. Horbar JD, et al. Weight Growth Velocity and Postnatal Growth Failure in Infants 501 to 1500 Grams: 2000–2013. Pediatrics. 2015. To be included, babies had to be hospitalized for between 15 and 175 days. Over the period studied the babies had slightly better growth moving from 11.8 to 12.9 g/kg/day. The number with postnatal growth restriction fell significantly, which means I guess that the NICUs included are doing a better job. But. In the last year of the study, 50% of the babies were discharged with a weight below the 10th percentile, and 27% below the 3rd percentile.

Which is not good. And can be improved.

19.9% of the babies were below the Fenton 10th percentile at birth.

The article defines postnatal growth failure (PNGF) as a discharge weight below the 10th percentile, which I don’t think is quite right. If a child is born on the 2nd percentile and discharged on the 9th percentile, you can’t really call that PNGF. We need a better definition of PNGF.

In our study, which we have presented at PAS, we called PNGF being discharged below the 10th percentile if you were born above the 10th percentile, and your z-score decreased by 0.5 or more. I am not sure if that is perfect either, as a baby born at the 60th percentile who falls to the 15th would not be defined as PNGF by either definition, but probably should be.

About 5 years ago we introduced enhanced nutritional protocols. We have examined and presented our outcomes for 2 years worth of babies under 1300g (therefore at slightly higher nutritional risk than the VON data) of whom 19% were under the 10th percentile at birth (using the same Fenton standards) so almost identical as a percentage to the VON data. When I look at our data using the VON definitions, there were 27% discharged below the 10th percentile and 6% below the 3rd percentile at discharge. Which is a substantially lower proportion than the VON data, but still, I think we can do better.

We also calculated the average change in z-scores (again derived from Fenton’s work) which is probably a better overall indicator of nutrition for the whole group. Our new protocols resulted in a reduction of z-score between birth and discharge of 0.39 compared to a reduction of more than 1 with our previous protocols.

We had 13% infants with postnatal growth failure by our definition. Which is still too high, I think. Also these definitions are based on body weight ; length and head circumference should also be measured (although measuring length accurately is a challenge) as indicators of skeletal growth and body composition. Our babies, with our enhanced nutritional protocols, had a head circumference z score change between admission and discharge of only -0.1, much better than the previous -0.6, but had a length z-score change of -1.5 compared to -1.7.

Continuing to improve these outcomes will probably require an increase in protein intakes; a review of our standards revealed that many babies were receiving less than the 4 g/kg/d of enteral protein for a growing preterm which is now recommended. We are in the process of further enhancing our intakes to try to further increase protein administration, with the hope that a further improvement in length outcomes, and in head circumference, but without an increase in adiposity will result.

Interestingly our enhanced protocols are similar to the standards suggested in a recent review article from Germany. Maas C, Poets CF, Franz AR. Avoiding postnatal undernutrition of VLBW infants during neonatal intensive care: evidence and personal view in the absence of evidence. Archives of Disease in Childhood – Fetal and Neonatal Edition. 2014. The main difference between their recommendation to start breast milk fortification at “no later than 100 mL/kg/day” and or protocol which starts when the babies receive 25 mL/day (which we chose so as to prepare a whole days feeds with at least one sachet of fortifier, and not throw away breast milk). That review article quotes 5 studies which all had good growth outcomes, and were all quite similar to our results, meaning I think that just about any NICU should be able to achieve similar nutritional/growth outcomes.


About Keith Barrington

I am a neonatologist and clinical researcher at Sainte Justine University Health Center in Montréal
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