Incidence and outcomes of uterine rupture in women with unscarred, preterm or prelabour uteri: data from the international network of obstetric survey systems.

OBJECTIVE

Analysis of atypical cases of uterine rupture, namely, uterine rupture occurring in unscarred, preterm or prelabour uteri.

DESIGN

Descriptive multi-country population-based study.

SETTING

Ten high-income countries within the International Network of Obstetric Survey Systems.

POPULATION

Women with unscarred, preterm or prelabour ruptured uteri.

METHODS

We merged prospectively collected individual patient data in ten population-based studies of women with complete uterine rupture. In this analysis, we focused on women with uterine rupture of unscarred, preterm or prelabour ruptured uteri.

MAIN OUTCOME MEASURES

Incidence, women's characteristics, presentation and maternal and perinatal outcome.

RESULTS

We identified 357 atypical uterine ruptures in 3 064 923 women giving birth. Estimated incidence was 0.2 per 10 000 women (95% CI 0.2-0.3) in the unscarred uteri, 0.5 (95% CI 0.5-0.6) in the preterm uteri, 0.7 (95% CI 0.6-0.8) in the prelabour uteri, and 0.5 (95% CI 0.4-0.5) in the group with no previous caesarean. Atypical uterine rupture resulted in peripartum hysterectomy in 66 women (18.5%, 95% CI 14.3-23.5%), three maternal deaths (0.84%, 95% CI 0.17-2.5%) and perinatal death in 62 infants (19.7%, 95% CI 15.1-25.3%).

CONCLUSIONS

Uterine rupture in preterm, prelabour or unscarred uteri are extremely uncommon but were associated with severe maternal and perinatal outcome. We found a mix of risk factors in unscarred uteri, most preterm uterine ruptures occurred in caesarean-scarred uteri and most prelabour uterine ruptures in 'otherwise' scarred uteri. This study may increase awareness among clinicians and raise suspicion of the possibility of uterine rupture under these less expected conditions.