Introduction: One of the reasons for the delayed hospital discharge of newborns is jaundice. The aim of this study was to analyze the mother’s gestational weight gain (GWG) as a factor contributing to jaundice in healthy, breastfed newborns, ≥ 37 weeks of gestation. Material and methods: The medical documentation of 3594 mother-newborn pairs was analyzed. The newborns’ gestational age, birth weight, birth weight loss (BWL) and the total serum bilirubin (TsB) on the 3 rd or 4 th day of life, as well as the mothers’ pre-pregnancy body mass index (BMI), and GWG were analyzed. The newborns were divided into three groups. Group I was composed of those without jaundice (n = 1258), group II with jaundice (TsB between 5 and 11.9 mg/dl; n = 1302), and group III with TsB ≥ 12 mg/dl (n = 1034). Results: The newborns from group I were more mature (p = 0.000) and had higher birth weight than newborns from groups II and III (p = 0.01). There was no difference in birth weight between groups II and III but newborns from group III were less mature (p = 0.03). There were no differences in BWL between the groups. Pre-pregnancy mean BMI of mothers from group III was higher; they more often were overweight (p = 0.000), but not obese. During pregnancy, they had a greater mean GWG (p = 0.000), and more often had excessive weight gain (p = 0.000), but also gestational diabetes (GDM) and hyperten- sion. On admission to the maternity ward, mothers from group III had higher mean BMI and more often were obese than mothers from groups II and I. Conclusions: Our study suggests that in addition to the known risk factors of early markedly elevated bilirubin concentration in healthy newborns ≥ 37 weeks of gestation such as lower birth weight and lower gestational maturity, the mother’s excessive weight gain during pregnancy and complications of pregnancy such as gestational diabetes and hypertension should be taken into consideration. KEY WORDS: BMI, gestational weight gain, newborn, jaundice, mother