Stress during gestation and multiple births can alter postpartum maternal care in sheep. The objective of this study was to determine the effect of LPS injection during the second and last third of gestation and the number of lambs born per ewe on maternal behavior and time to first suckling. Pregnant multiparous crossbred Santa Ines ewes were challenged with an intravenous administration of 0.8 μg·kg⁻¹ of lipopolysaccharide E. coli, or saline. Forty-two ewes were placed in individual pens with full open view of other animals, inside of a barn, during an adaptation period of 5 d. Ewes had free access to water, shade and food. Ewes were divided into 3 groups: CG - control group, (n = 14) that were not subjected to LPS injection; SG – stress at second third of gestation (70 d; n = 14); LG – LPS injection during the last third of their gestation period (120 d; n = 14). Behavior was recorded as positive (facilitated and encouraged suckling) and negative maternal behavior (aggressive, lack of co-operation with the lamb’s sucking attempts) using 1-min scan sampling interval. Data were recorded from the time of birth until the first effective suckling event. If there were multiple births (2 lambs), each lamb was assessed separately. Data were analyzed as a completely randomized design using MIXED/SAS, and the ANOVA model had gestation LPS injection and the number of lambs born as the fixed effects as their interaction. Differences between LPS injection periods x birth were significant at a P < 0.05. Mother-offspring positive interactions were observed more than negative interactions (P < 0.05), except for the LG with multiple births, where the opposite occurred. Negative interactions were only observed in ewes with multiple births (P < 0.05). Lambs born from ewes in SG and LG groups, in twin births, spent more time until the first suckling (P < 0.05). It is likely that the delay in colostrum intake decreases the immunological capacity of the lamb, and the success of the ewe and lamb bond. LPS injection, which mimics a disease process, in late pregnancy is more harmful to the newborn lamb increasing negative maternal behavior and the time to first suckling.