Introduction: there is scarce evidence of the effects of obesity and gestational weight-gain (GWG) on hemoglobin (Hb) levels in pregnancy. Little is known about the implications in offspring when pregnant mothers present with both at delivery. Aim: to identify if pre-pregnancy body mass index (BMI) and GWG are associated with Hb levels at pregnancy third trimester; and identify if the BMI status plus anemia at delivery could influence offspring anthropometry. Methods: in a sub-sample of pregnant women (n = 108) and their offspring (n = 63) from a Mexican birth cohort, information from medical files and questionnaires were used to obtain pre-pregnancy BMI (categorized as normal, overweight, and obese), GWG, and Hb during pregnancy; at delivery and postpartum anthropometric measures were obtained for offspring. Adjusted regression models predicted Hb levels according to pre-pregnancy BMI and GWG; offspring growth trajectories from birth to 3 months old were compared according to mother´s BMI status and anemia combinations at delivery. Results: pre-pregnancy normal (N), overweight (OV), and obesity (OB) were present in 48 %, 40 %, and 12 % of the participants, respectively. Anemia was detected in 22.8 % of the participants at third trimester. Hb levels in the third trimester were significantly lower in those with pre-pregnancy OB-BMI and excessive GWG (12.1 g/dL, 95 % CI: 10.7-13.5) compared to those with pre-pregnancy OB-BMI and insufficient GWG (13.3g/dL, 95 %CI: 11.9-14.8) (p = 0.04). At delivery, 11 % presented with OB-BMI and anemia. Women with OB-BMI and normal Hb levels had children with higher scores in Weight-for-Length-Z score and triceps skinfold. Conclusion: among OB women, excessive GWG was associated with having lower Hb levels in the third trimester. Newborns had higher scores in growth patterns related to adiposity from birth to 3 months old if mothers had normal Hb levels and OB.