TF and atrial fibrillation: No differences were observed in the difference in weight z score (SD) between the following different studied time points: at 28 days after initiation of fortification [AF −0.82 (0.62) vs. TF −1.18 (0.60), p = 0.09], at 36 weeks PMA [AF −1 (0.67) vs. TF −1.23 (0.75), p = 0.36], and at discharge [AF −0.9 (1.03) vs. TF −1.13 (0.57), p = 0.38].