LONDON – Extremely low birth weight infants need extended follow-up for renal problems, according to a 7-year follow-up of Polish children born between 2002 and 2003.
The regional cohort study results show that, at a mean age of 6.7 years, kidney function was not only significantly reduced in extremely-low-birth-weight (ELBW) infants vs. normal-weight control subjects, but that several ELBW children had hypertension.
Furthermore, renal volume was significantly lower in the ELBW children, with 13 (18%) of 72 children having smaller-than-expected kidneys for their age (P = .04).
"Survival rates [among ELBW infants] are now pretty good, so we have an increasing number of school-aged children," the study’s lead author Dr. Przemko Kwinta said in an interview at the Excellence in Paediatrics annual meeting.
"Traditionally we think about the mental development, the motor development, but there’s a lot of risk factors during early life that can also influence the kidney," Dr. Kwinta, head of the department of pediatrics at Jagiellonian University in Krakow, Poland, said. "We think that there are a lot of babies with borderline [renal] function, so maybe it is necessary to introduce some type of prophylaxis."
ELBW during the study was defined as a weight of less than 1,000 g at birth. Of 95 children born in the Malopolska district of Poland between 2002 and 2003, 72 infants had a mean birth weight of 841 g, and 23 had a mean birth weight of 3,559 g.
The mean gestational age of the ELBW and normal-weight infants was 27.3 weeks and 39.9 weeks, respectively, and the mean age at follow-up was 6.7 and 6.9 years.
Mean estimated glomerular filtration (eGFR) rates were significantly lower (94.8 vs. 103.9 mL/min per 1.73 m2; P less than .01) in the ELBW vs. the normal-weight groups, but the mean serum cystatin C level was higher (0.64 vs. 0.57 mg/L; P less than .01) in the ELBW group. However, in all children, both eGFR and cystatin C were within normal ranges.
Hypertension was observed in three (4.1%) of ELBW infants but in none of the normal-weight children (P = .1). Three ELBW children also had microalbuminuria, which was not seen in any child in the control group.
The mean volume of both the left and right kidneys was reduced in the ELBW children vs. the control group, and small kidneys (defined as less than 70% of the predicted size) was detected in 13 ELBW children, but none of the control children (P = .04).
Based on their clinical experience Dr. Kwinta and associates believe that ELBW infants require very close renal follow-up.
"We have to check the renal function, not only after birth or at 1 year, but also after 3, 6, and 7 years because the prevalence of renal problems is quite high," Dr. Kwinta observed. This may help us to recognize the early stages of renal disease so that problems in later life can be prevented.
Further follow-up of the cohort is planned at ages 10 and 11 years.
The Polish Ministry of Science supported the study. Dr. Kwinta said he had no relevant financial disclosures.