|Objective To evaluate the effectiveness and safety of mechanical preinduction cervical ripening before labour induction using osmotic cervical dilators (Dilapan-S). Method A retrospective study of 68 patients who gave birth at the Gynaecology and Obstetrics University Hospital Brno in 2010-2011 in whom the osmotic cervical dilators Dilapan-S were used for preinduction cervical ripening before labour induction. Only patients who completed the 36th week of gestation and who had a singleton pregnancy with the fetus's head in the longitudinal position were included. Efficacy of preinduction and mode of delivery weres assessed. The incidence of contraction activity during preinduction, uterine hypertonus, signs of intrauterine fetal distress and infectious complications in the mother and newborn were evaluated. Results The most common indications for preinduction cervical ripening were post-term pregnancy (38.2%), diabetes mellitus (19.1%) and maternal hypertensive disorders (10.3%). Previous caesarean section was present in the medical history of 16 patients (23.5%). The mean cervix score before preinduction was 2.9 (minimum 2, maximum 4) and 6.1 after preinduction. A final cervix score of 5 or more was achieved by 54 patients (79%). In three cases, three lots of Dilapan-S were applied and all achieved a cervix score >5. In all other cases, two lots of Dilapan-S were applied. The mean duration of preinduction was 14 hours 21 minutes. Contraction activity during preinduction was observed in 18 patients (26.5%), rated as mild by 16 patients. Cardiotocography (CTG) during preinduction was performed in 67 patients (98.5%). Uterine hyperactivity was not recorded. Thirty-seven patients (54.4%) delivered vaginally, 31 patients (45.6%) delivered by caesarean section. When comparing the subgroup of patients with a caesarean section in their medical history (n = 16) and the subgroup of patients without previous caesarean section (n = 52), there was no significant difference in the ratio of completed vaginal birth (50.0% versus 53.8%). A pH value of 7.10 or lower was found in five patients (7.3%). In the subgroup of patients with a history of caesarean section, a pH value of 7.10 or less did not occur. No 5 minutes Apgar scores less than 5 were observed. Two patients had postpartum febrile illness treated with antibiotics therapy, which in one case was evaluated as pyelonephritis and in the second case as in open abdominal wound infection after caesarean section. Four infants (5.8%) were treated for acute conjunctivitis which corresponds to the average incidence in the population. No other complications in the mother or infant were recorded. Conclusion The osmotic cervical dilators Dilapan-S are highly effective and safe in preinduction cervical ripening before labour induction in patients with an unfavourable cervix score. The advantage is the low incidence of adverse contractile activity during preinduction. Dilapan-S can be effectively used even in patients with a history of previous caesarean section. Infectious complications in mothers and newborns in our sample were not recorded.