Birth weight appears to be a key indicator for survival and average daily gain (ADG) in piglets. However, parameters associated with piglet antimicrobial treatment are less explored. We assessed the factors influencing piglet survival, ADG, and first individual antimicrobial treatment. Data were collected on sex, weight, litter details, and medication throughout the lifespan of 3991 ear tagged pigs in Finland. Discrete-time survival models were performed for piglet survival and individual antimicrobial treatment as well as a linear regression model for piglet ADG from birth to slaughter. Medium (1 - 1.49 kg) and lightweight (<
1.0 kg) piglets at day 4 had 2.26 and 4.04 times higher odds of dying (in terms of odds for discrete hazards), respectively, than heavyweight (≥ 1.5 kg) piglets. Barrows and antimicrobial-treated suckling piglets had 1.81 and 1.67 times, respectively, higher odds of dying than females and unmedicated piglets. The mean average daily gain from birth to slaughter was 714 g (SD 70.2 g). Pigs born to sows grew 29.2 g/day more than pigs born to gilts, and barrows grew 13.3 g/day better than females, but these results should be interpreted with caution because a considerable number of ear tags lost during the study could have led to selection bias of the pigs with a measured ADG. Altogether 756 piglets received at least one individual parenteral antimicrobial treatment. Antimicrobial-treated pigs were to a considerable extent medicated before weaning mainly for diarrhea and leg problems during two treatment peaks: before day 8 and around weaning. Lightweight piglets at day 4 had 2.35 and piglets born to gilts 1.56 times higher odds of becoming medicated with antimicrobials than heavyweight piglets and piglets born to sows, respectively. Half of the study piglets receiving antimicrobials were treated again later. In summary, our results show that lightweight piglets at day 4 had poorer survival, and they received more antimicrobial treatments than their heavier littermates. Further, gilt offspring were medicated more frequently. This emphasizes the need to direct extra attention to litters born to gilts.