Sow nutrition plays a crucial role impact on fetal and neonates’ development, lactation and lifetime production of piglets. In this field study, our aim was to evaluate the impact of two feed supplements, namely vitamin C (VC group) and a combination of vitamin C and ferrous sulfate (VC+Fe group), administered during the last trimester of pregnancy, on sow's blood hemoglobin (Hb) concentration and individual birth weight of piglets. The sows came from hyper-prolific genetic lines (Topigs Norsvin Ninety pregnant sows were randomly divided into three groups: 31, 29 and 30 individuals for the C (control), VC and VC+Fe groups, respectively. We measured individual Hb concentration I (Hb I) on day 76 of pregnancy for all groups, prior to the start of supplementation in the VC and VC+Fe groups. A second measurement (Hb II; antepartum hemoglobin) occurred 2–4 days before the estimated farrowing date for each sow. We recorded the individual birth weight (kg) of 376 piglets in the C group, 403 piglets in the VC group, and 392 piglets in the VC+Fe group. Both the VC and VC+Fe groups showed improvement in Hb II (P = 0.005), improving their hematological status; however, there was no significant advantage of VC+Fe over VC in terms of Hb II. The effect of group on individual birth weight of piglets varied depending on the parity of the mother (P = 0.001). The supplementation with both VC and VC+Fe demonstrated positive effects on the birth weight of piglets, but only in sows with parity 1 and 2 (P < 0.001). These results suggest that additional iron supplementation did not confer significant benefits beyond what was already provided in the pregnancy feed. Therefore, the inclusion of vitamin C supplementation alone appears to be sufficient.