Based sa what I know, 2.3kg at 35 weeks is a bit on the lighter side, most babies around that time ay around 2.4-2.6kg na, pero hindi rin alarming kasi may normal range pa rin talaga depende sa genetics at maraming factors. I'd really suggest asking your OB about it sa next checkup para sure, especially if they want to monitor baby's growth more closely, kasi sila lang makikita ang full picture ng development mo at baby mo together!