The construction of referral curves for the computerized ctg parameters may increase the clinical efficacy of the examinations in tracings of unfavourable interpretation. With the help of "System 8000" software, the longitudinal variation of computerized parameters fetal movements/hour, fetal movements in high and low variability, accelerations, length of high and low variability periods, mean range and value of short variability have been analyzed in a group of 12 low risk patients followed biweekly from the 24-26th week of gestation through term. While accelerations, minutes of low and high variability showed an absence of significative variation during pregnancy (F = 1.78; F = 9.3, F = 4.5 P = n.s.), significant (p less than 0.001) variation showed the other parameters. Number of movements/h and movements in high variability had an increase from 24-26 weeks to 32-34 weeks and a progressive further decrease till term; movements in low variability disappear after 32-34 weeks of gestation; mean range and short variability increase until 34 weeks and remained stable till end. Therefore the results obtained are in use for the high risk fetuses that perform a computerized ctg registration: nevertheless, the longitudinal evaluation reveals the maturation of fetal central nervous control on heart rate and fetal movements after the 34-36th weeks of gestation as a shown from behavioural states evaluation.