Metformin has been used for the treatment of some metabolic diseases during gestation and the beneficial effects of metformin to the vascular system have been described in diabetic and obese animal models. Nevertheless, the long-term consequences to the vascular system of offsprings maternally exposed to metformin have not yet been characterized. Therefore, we want to test the hypothesis that gestational and lactational exposure to metformin would be safe for the vascular reactivity of male adult offsprings. Wistar female rats were treated with metformin 293 mg·kg·d, by gavage, from gestational day (GD) 0 to GD 21 (METG) or GD 0 until postnatal day 21 (METGL). Control dams received water by gavage in the same periods (CTRG and CTRGL). In male offsprings (75 days), the aortic reactivity to phenylephrine, acetylcholine, and sodium nitroprusside in the presence or absence of endothelium were evaluated. The results demonstrated that aortic contraction and relaxation were similar between groups. These data showed that metformin exposure during pregnancy and lactation did not interfere with aortic reactivity, suggesting that metformin exposure during gestational and lactation are safe for the offsprings' vascular system.