Perineal Injury in Nulliparous Women Is Reduced With Certified Nurse Midwives

Marilyn W. Edmunds, PhD, CRNP


June 29, 2010

Perineal Injury in Nulliparous Women Giving Birth at a Community Hospital: Reduced Risk in Births Attended by Certified Nurse-Midwives

Browne M, Jacobs M, Lahiff M, Miller S
J Midwifery Womens Health. 2010;55:243-249

Study Summary

Perineal injury occurring with labor and delivery is associated with a variety of short- and long-term consequences. Previous research suggests that postpartum perineal pain, sexual dysfunction, and delayed time to resume sexual intercourse are frequent byproducts of perineal injury, with some women still experiencing significant problems up to a year after giving birth. The resulting perineal pain and sexual problems have also been linked to postpartum depression.

Objective. The study sought to determine whether rates of perineal injury sustained by nulliparous women who were attended by obstetricians differed in comparison with births attended by certified nurse-midwives (CNMs) at one US community hospital.

Methods. The study involved a retrospective cohort analysis of 2819 women who spontaneously gave birth in community hospitals to singleton, vertex, term, live infants between 2000 and 2005. The independent variable was attendant type (obstetrician or CNM). The main outcome variables were intact perineum, episiotomy, and spontaneous perineal lacerations. The literature suggested that certain factors might influence the incidence of perineal injury; thus, multivariate logistic regression was used to adjust for 6 potential confounding variables: macrosomia, maternal age, epidural anesthesia, oxytocin administration, medical insurance status, and ethnicity.

Results. The prevalence and severity of perineal injury, both from spontaneous lacerations and episiotomy use, were significantly higher in obstetrician-attended births. The odds ratio (ORs) for obstetrician-attended births vs CNM-attended births were significant for a spontaneous minor perineal laceration vs intact perineum (OR, 0.82; 95% confidence interval [CI], 1.33-2.48); spontaneous major laceration vs intact perineum (OR, 2.29; 95% CI, 1.13-4.66); and episiotomy vs no perineal injury, with or without extension (OR, 2.94; 95% CI, 2.01-4.29).

Discussion. This study differs from others in the literature in 2 major ways: (1) it collected data from births in a community hospital rather than a teaching hospital or a maternity care center; and (2) it adjusted for variables that are known to be associated with perineal injury. The large sample size and collection of data over a 6-year period are strengths of the study. A weakness of the study is that no information about the birth attendant’s years of practice experience was provided. Evidence that less perineal injury is associated with more experienced birth attendants, regardless of profession, suggests the importance of this variable.


The findings of this study agree with other research on this topic. This research was conducted in northern California by an interdisciplinary team of 2 registered nurses (including one with a PhD who was also a CNM), a physician, and a PhD statistician. When comparisons are made between care of different providers, an interdisciplinary research team helps in crafting research designs that are seen as both credible and unbiased. When research findings can be generalized, the team often helps disseminate findings to other professionals so that changes in practice are more likely.

What the research does not identify are the differences in birth practices between CNMs and obstetricians that result in fewer perineal injuries in CNM-attended care. The investigators suggest that CNMs typically encourage the mother to be in a nonsupine position for the second stage of labor and birth and also promote noncoached pushing. But no research has yet examined whether these techniques reduce the risk for perineal injury.

My own observations of CNM deliveries suggest that CNMs as a group tend to spend significant time during the later stages of labor massaging the perineum, sometimes employing lotions or ointments, and attempting to gradually stretch the perineum before the final stage of labor. CNMs tend to suggest to mothers that an intact perineum is possible and that they will work to help achieve it.

Additional research might help identify the factors responsible for lowering the rate of perineal injury. The next step would be to share with obstetricians the findings about CNM practices that avoid perineal injury.



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