Preterm birth is a highly prevalent phenomenon that was shown to be associated with mental stress during pregnancy (Rich-Edwards and Grizzard in Am J Obstet Gynecol 192(5 Suppl):S30-S35, 2005). We aimed to assess the effects of heart rate variability (HRV)-biofeedback in patients with preterm labour. Therefore, we conducted a controlled randomized parallel group study in 48 female patients aged 19-38 years (median = 29) with preterm labour at gestational week 24th-32nd (median = 29th). In this study, one group (n = 24) attended six sessions of HRV-biofeedback over 2 weeks whereas patients of the other group (n = 24) were assigned to control sessions. In the HRV-biofeedback treated group, perception of chronic stress was decreased 4 weeks after completion of training compared to baseline (p < 0.05) but there was no change in the control group. In the HRV-biofeedback group, preterm birth was seen in 3 patients (13 %) whereas in the control group, preterm delivery occurred in 8 patients (33 %, p = n.s.). There was no difference in birth weight between groups and HRV remained unchanged. In conclusion, our study demonstrates that HRV-biofeedback can reduce chronic stress in patients with preterm labour when administered as an adjunct to routine care. However, it remains unclear whether stress reduction through HRV-biofeedback has a beneficial effect on preterm birth.