Growth and body composition of infants born moderate-to-late preterm fed an protein- and mineral-enriched postdischarge formula compared with a standard term formula up to 6 months corrected age, a randomized controlled trial

Background: Infants born moderate-to-late preterm (i.e., 32 ⁰/₇-35 ⁶/₇ weeks' gestation) are, analogous to those born very preterm, at risk of later obesity, hypertension, and diabetes. Appropriate early life nutrition is key for ensuring optimal growth and body composition, thereby mitigating potential cardiometabolic risks.

Objective: To compare growth and body composition between infants born moderate-to-late preterm fed isocaloric but protein- and mineral-enriched postdischarge formula (PDF) or standard term formula (STF) until 6 months corrected age (CA; i.e., after term equivalent age [TEA]).

Methods: After enrolment (≤7 days postpartum), infants received PDF if (fortified) mother's own milk (MOM) was insufficient. At TEA, those receiving >25% of intake as formula were randomized to either continue the same PDF (n=47) or switch to STF (n=50); those receiving ≥75% of intake as MOM (n=60) served as references. At TEA and 6 months CA, we assessed anthropometry and body composition using both dual-energy x-ray absorptiometry and air displacement plethysmography.

Results: Feeding groups had similar gestational age (median [p25;p75]: 34.3 [33.5;35.1] weeks), birthweight (mean ± SD: 2175 ± 412 g), anthropometry and body composition at TEA. At 6 months CA, infants fed PDF had slightly, but significantly, higher length (67.6 ± 2.5 and 66.9 ± 2.6 cm, p<0.05) and larger head circumference (43.9 ± 1.3 and 43.4 ± 1.5 cm, p<0.05) compared to infants fed STF. Also, infants fed PDF had higher lean mass and bone mineral content estimated by dual-energy x-ray absorptiometry (4772 ± 675 and 4502 ± 741 g; 140 ± 20 and 131 ± 23 g, respectively; p<0.05). Air displacement plethysmography estimates, however, were not statistically different between feeding groups.

Conclusions: Infants born moderate-to-late preterm demonstrated modest increases in length, head circumference, lean mass, and bone mineral content when fed PDF compared to STF for 6 months after TEA.

Clinical trial register: International Clinical Trial Registry Platform (https://trialsearch.who.int) as: NTR5117 (old-NTR) and NTR NL4979 (new-NTR) .