Results of prospective studies of 1404 consecutive vaginal and cesarean deliveries of newborns weighted > or = 2500 g were analyzed in relation to their maturity. It was stated that Ballard Maturation Score is a valid accurate assessment tool for precise interpretation of the degree of fetal maturity, but not of the calendar length of gestation, especially beyond 36 weeks. Therefore it was reasonable to propose a constant distribution of scores: 39 +/- 3 points within the period from 37% to 43% weeks while at the 28th week: 10 +/- 2 points (Ballard-Klimek scale of pregnancy dating) instead of therefore used J. L. Ballard rule that only newborns at 44 weeks can have scores of 50 and infants with shorter gestational age have lower values, e.g. 33 at the 37th week.