November 01, 2019
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Low weight at birth associated with eGFR decline; CKD screening should begin at age 9

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Study participants born with low birth weight had lower eGFR when compared with infants of normal birth weight — a finding that remained consistent through adolescence and young adulthood — leading researchers to recommend screening this population for CKD at 9 years of age.

“While [multiple] studies have highlighted the long-term renal consequences in [low birth weight] LBW neonates, few studies have investigated the progression of kidney dysfunction through the pediatric years leading up to young adulthood,” Xixi Zhao, MD, of the department of internal medicine and pediatrics at Rush University Medical Center in Chicago, and colleagues wrote. “One study demonstrated an increase in microalbuminuria in children as young as 8 years old who were born premature. However, it did not differentiate between individuals who were born with LBW and those who had an acute kidney injury event while in the [neonatal] NICU. This makes it difficult to discern if being LBW alone is a relevant risk factor for CKD.”

To account for this and other limitations — including small sample size, limited racial diversity and incomplete medical histories — of previous studies, researchers examined the temporal effects of birthweight on kidney disease progression comparing GFR between individuals born with low and normal birth weight at ages 1 year to 26 years. Participants were categorized by age group as 1 year to 8 years, 9 to 16 years and greater than 16 years of age.

For individuals older than 9 years, investigators found GFR was significantly lower in participants born with low birth weight than those born with normal birth weight (mean difference 5.5 mL/min/1.73 m2), suggesting that low birth weight is a risk factor for GFR decline. This difference was especially pronounced in participants born with extremely low birth weight (defined as less than 1,000 grams).

Infant 
Study participants born with low birth weight had lower eGFR when compared with infants of normal birth weight.
Source: Adobe Stock

In addition, while GFR increased from the youngest- to the middle-age group and declined from the middle- to oldest-age group for both cohorts, it was consistently lower in all three age groups in those born with low birth weight.

Regarding racial differences, researchers noted that the impact of low birth weight on eGFR was observed only for Hispanic/Latino and white participants, with no effect seen for black participants. A similar contrast was seen between male and female participants: male participants born with low birth weight had lower eGFRs than those born with normal birth weight, but this difference not observed in female participants (they suggested this may be because male participants exhibit earlier signs of GFR decline than women but progress to ESRD later in life).

Finally, although GFR remained within the normal limits for those born with low birth weight, researchers predicted that it will “decline more rapidly” for these patients due to previous studies that have demonstrated an increased risk for CKD and ESKD in adulthood.

“In addition to blood pressure measurements, we recommend a screening [urinalysis] UA and renal function panel for those born with [extremely low birth weight] ELBW starting at the age of 9 years, as the two oldest cohorts experienced the most pronounced GFR differences when compared with participants born with [normal birth weight] NBW,” they concluded. “Unfortunately, it is during this adolescent time period when many will see their pediatricians less frequently. Every effort should be made to have these patients made aware of their risk for future CKD and the importance of following up and counseling regarding modifiable factors for CKD progression, such as smoking, hypertension and obesity.” – by Melissa J. Webb

Disclosures: The authors report no relevant financial disclosures.