Objective: To compare severe maternal and infant outcomes from uterine ruptures (URs) among women with unscarred uteri versus women with a prior cesarean.

Design: Matched case-control study

Setting: Massachusetts

Patients/Participants: Women in the Massachusetts UR Study with a singleton pregnancy of ≥20 weeks gestation, no trauma, and labor. Cases were all women with unscarred uteri meeting criteria and controls were randomly chosen among women with UR meeting criteria who had a prior cesarean. 

Methods: All URs in Massachusetts between 1990 and 1998 were identified using ICD-9 codes from linked hospital discharge and birth/fetal death certificate files. UR was confirmed by medical record review.  Maternal data were abstracted from maternal hospital records by trained maternity nurses. Severe maternal outcomes were defined as: death, hysterectomy, transfusion, ICU admission, or assisted ventilation.  Two neonatologists independently reviewed infant records to identify death related to the UR and assess prognosis at discharge.  Each case was matched with two control women on delivery year ±2 years and gestational age ±2 weeks. T-tests and chi-square statistics were used as appropriate. Conditional logistic regression generated odds ratios and 95% confidence intervals. 

Results: Of the 49 URs in women without a prior cesarean, 36 women had unscarred uteri and met study criteria and were matched to 72 control women. Exact matches on delivery year and gestational age occurred in 85% of the controls. Case and control women did not differ on sociodemographic variables. Control women had a higher parity since they had at least one prior cesarean. Case women experienced more D&Cs (p=0.023).  The two groups did not differ by hospital level, oxytocin or epidural use.

Women with unscarred uteri were four times more likely to have severe morbidity (OR 4.19; 95% CI: 1.72, 10.19) with half requiring hysterectomy, 47% transfusion, and 33% ICU admission.

Although both groups experienced the same percent of individual signs of UR (pain, vaginal bleeding, non-reassuring fetal status), 58% of case women had ≥2 of these signs versus 29% of controls. Of case women, 86% experienced a severe maternal morbidity.  Case women’s hospital stays were two days longer than women with a prior cesarean. Infant outcomes did not differ between groups.  

Conclusion/Implications for nursing practice: Although UR in a woman without a prior cesarean is uncommon, when it occurs obstetrical providers should be prepared for more severe maternal morbidity which may be mitigated with prompt surgical intervention and heightened hemodynamic surveillance.

Keywords: uterine rupture, unscarred uterus, prior cesarean, maternal morbidity