Changes in Postpartum Perineal Muscle Function in Women With and Without Episiotomies

Nancy Fleming, CNM, PhD, Edward R. Newton, MD, Joyce Roberts, CNM, PhD


J Midwifery Womens Health. 2003;48(1) 

In This Article


The perineal outcomes of 102 study subjects are summarized in Table 1 . Of the 10 women receiving episiotomies, two were done at the parturient's request (one request made because of the patient's fear of "tearing" and one because the patient thought a tear might make her vaginal introitus "looser").

Two episiotomies were performed because the fetal heart rate suggested intolerance to labor. Three were performed because meconium-stained fluid signaled possible fetal distress, and three were performed for a prolonged second stage of labor with an unyielding perineum. One woman experienced a fourth-degree extension of her episiotomy, and one woman without an antecedent episiotomy sustained a third-degree laceration.

In comparing perineal outcomes relative to initial demographic and obstetric characteristics, the groups were remarkably similar and did not differ significantly with respect to age, birthweight of infant, or 1-, 5-, and 10-minute Apgar scores. The only statistically significant difference was found in the group delivered by cesarean, which was composed of a larger number of primigravidas than any of the vaginal birth groups. The percentage of infants born weighing more than 4000 g was similar in all outcome groups. There was no evidence that infant birthweight had any effect on either absolute postpartum perineal muscle function scores or on the direction of change in the postpartum scores.

In both peak and endurance measurements of perineal muscle function, scores of nulliparous, non-pregnant women were significantly higher than those of nulliparous pregnant women; that is, the mean "peak" scores for the non-pregnant women was 9.9 mcV compared to 4.8 mcV for the pregnant women, and the mean "endurance" scores were 5.7 mcV versus 2.2, indicating a reduced perineal muscle performance during pregnancy (P = <.001).

Serial antepartum perineal muscle function scores in the pregnancy group generally tended to increase from week to week during the study period. Mean antepartum peak and endurance muscle function scores were similar for all outcome groups, with statistically significant differences between the antepartum values and postpartum values when the groups with the highest and lowest mean scores were compared. The women with the highest mean peak and endurance muscle scores antenatally were the group of women who eventually received an episiotomy. Although the range of peak and endurance antepartum scores was similar in both groups, the mean antenatal scores in the group of women who eventually sustained second-degree lacerations during birth were the lowest, and that group was significantly different compared with the highest (episiotomy) group. Postpartum, the women with intact perinea had the highest mean scores for both peak and endurance. Women who sustained a second- or third-degree laceration had the lowest peak and endurance values (P = .01) There were no significant differences in postpartum mean peak or endurance scores between the laceration and episiotomy groups ( Table 2 ).

Mean peak and endurance scores rose in all groups postpartum except the episiotomy group. The greatest increases were in the group of women with intact perineums, followed closely by the group of women who had a cesarean birth (Figure 2). Because the critical comparison of the study was between pre- and postdelivery perineal muscle function at its best, the decision was made to compare the highest antepartum scores, whenever those measurements occurred during the weeks preceding delivery, with the highest postpartum scores, whether those occurred at the 6-week or the 6-month measurement.

Comparison of antepartal and postpartal muscle score means and standard deviations for women with different perineal conditions.

In summary, antepartum and postpartum peak and 10-second endurance scores of women in all outcome groups were similar. After controlling for parity, the order of best to worst postpartum perineal muscle performance was cesarean birth, intact perineum, first-degree laceration, second- or third-degree laceration, and finally episiotomy. Although the mean peak and endurance scores in the perineal outcomes groups did not differ significantly, analysis of the change in both peak strength and endurance scores between the antepartum and postpartum periods revealed that all groups increased postpartum muscle function except the episiotomy group, in which mean peak and endurance scores decreased. This decrease in mean scores for the episiotomy group compared with an increase in mean score in all other outcome groups represented a significant change of muscle function measurements. The range of antepartum scores for women without episiotomy was similar regardless of their eventual perineal outcome, making it impossible to use individual scores prospectively to predict whether a woman would have an intact perineum or sustain a laceration at delivery in the absence of an episiotomy.

The study was undertaken to evaluate perineal muscle function before and after childbirth in a prospective manner using an objective, standardized instrument for measurements of perineal muscle strength and endurance. Our data from the non-pregnant, nulliparous control group suggest that a decrease in perineal muscle function occurs normally during the antepartum period, possibly in response to the altered hormone status of pregnancy. Like other investigators,[11,13,15,16,17,18] we found general rises in perineal muscle function in the postpartum period, although in our data the mean scores of parous women with any perineal outcome, including those with cesareans, were lower than those of the nulliparous group.

Like Klein et al.,[14] our testing found no significant differences in absolute postpartum perineal muscle strength or endurance between the episiotomy and laceration groups in the postpartum period. However, comparison of the antepartum and postpartum muscle function scores suggested that the degree to which women regained perineal muscle function after birth was positively related to perineal trauma at delivery: those with the least perineal trauma (the intact and cesarean groups) had the greatest positive change in scores. The finding that the group of women who received an episiotomy was the only group to exhibit a net loss of perineal muscle function after delivery is consistent with that of Rockner et al.[19] and adds further support to the contention that routine episiotomy or episiotomy to prevent a laceration may actually contribute to a decline in function.

External validity is a concern in interpreting the results of this study. Because of the relatively small, homogeneous characteristics of both study subjects and birth attendants, care must be used in attempting to generalize the results to other settings and populations. In addition, because subjects were voluntary participants in the research, the question must be raised as to possible bias owning to interaction between subjects and birth attendants. It is possible, for instance, that a subject's relationship with the birth attendant may have colored subjective responses to study questions and perhaps have led to a different level of effort in the muscle function portions of the study.

The issue of "training effect" on perineal muscle function must also be addressed. Although it was outside the specific intent of this study to examine this area, it was clear throughout the serial testing portion of this study that perineal muscle scores could be raised significantly by diligent perineal training exercises. For example, although scores of women who did not have an episiotomy tended to rise somewhat between the 6 weeks and 6 months postpartum measurements, some women in all outcome groups registered their best muscle function scores at the 6-week measurement and then had small declines by 6 months. When questioned, these women often stated they had performed perineal muscle exercises diligently as instructed during pregnancy and until their 6-week postpartum check but had decreased or stopped them altogether after that. However, because of the reliance on self-reported data for quantification of amount of perineal training, an attempt at correlating the amount of perineal exercise with perineal muscle function was abandoned as being too subject to reporter bias. Dougherty et al.[20] attempted to examine the effects of a daily 10-minute perineal exercise program on the perineal muscle function of postpartum women. Their results found greater improvement in the exercise group than in the control group but found no statistically significant differences between the groups. Their finding would suggest that although perineal training effects can be observed, they do not have profound or long-lasting impact on perineal muscle function scores. Likewise, Gordon and Logue[21] looked at postpartum perineal muscle function in a retrospective fashion 1 year after delivery. They found the efficiency of perineal muscle function to be unrelated to perineal trauma but to be related to both perineal exercise and physical exercise in general. The effect of perineal training on muscle function certainly deserves examination in a controlled study design.

Factors that have been identified as possible contributors to muscle function changes were eliminated (gestational diabetes) or controlled statistically (antepartum muscle function, parity, maternal age less than 35 years, birthweight greater than 4000 g, and smoking), so these factors can be ruled out as accounting for the decline in function noted in the episiotomy group.

It was interesting to note that in this study, the women who eventually received an episiotomy at birth had higher antepartum scores than any other group. The reason for this finding is unclear, and the small numbers and heterogeneous reasons for performing episiotomies in this group do not lend themselves to hypotheses. However, because 3 of the 10 women who received episiotomies did so because of "unyielding" perinea, it is a possibility that this group contained a disproportionate number of statistical outliers, or there may be a real relationship between very high antepartum perineal muscle function scores and perinea that are unyielding during the birth process.

Postpartum perineal muscle function scores were inversely related to increasing tissue disruption in the non-episiotomy groups (Figure 3) .

Change in perineal muscle score means after birth in women with different perineal conditions.

The greatest increases in both strength and endurance, and indeed the very highest absolute postpartum scores, were found in the two groups with no muscle disruption—the intact and the cesarean groups, with very little difference between the two, either in amount and direction of change or in absolute scores. The progressive decline in postpartum muscle function restoration from the first-degree laceration group to the second- or third-degree laceration group adds additional support to the hypothesis that the greater the perineal tissue disruption at childbirth, the less the improvement of postpartum muscle function on the average. Thus, a possible explanation for the decline in episiotomy versus laceration scores is that, although both a second-degree laceration and an episiotomy are technically classified in the same category of perineal muscle disruption, in actuality many second-degree lacerations are shorter and/or shallower than a routine episiotomy, thereby disrupting less muscle. Another possibility is that women who received episiotomies were not as motivated to perform perineal exercises despite instructions to do so. This interpretation would explain a decrease in muscle function scores of the episiotomy group but would fail to account for the progressive decline in postpartum scores noted in the other tissue-damaged groups.

A final remaining issue is the frequently encountered assertion that perineal management and perineal condition after delivery will have a long-term effect on pelvic supports and perineal muscle function, not apparent until years after delivery. This hypothesis is difficult to entertain when research to date has shown that in the absence of episiotomy, postpartum perineal muscle function by 1 year after delivery has met or surpassed antepartum levels. It is possible to identify others factors that might impact muscle function through the years, such as frequent high-impact exercise, declining estrogen production, and heredity. Alternately, it is possible to assert that muscle groups measured by the vaginal myograph in the study are different from those muscle groups that prevent prolapse and urinary incontinence. However, if indeed there is a connection between long-term pelvic support and perineal muscle function, then it appears to be a tenuous position to assert that perineal muscle function, once completely restored after childbirth, will at some time in the future deteriorate based on perineal management.

In summary, the changes noted in postpartum perineal muscle function between groups of women with different perineal conditions following childbirth showed no difference in postpartum perineal muscle strength or endurance among any of the perineal outcome groups, adding evidence to the conclusion that episiotomy as a perineal management strategy to preserve or promote better perineal muscle function after delivery cannot be supported through scientific examination. Absolute perineal muscle function appears unrelated to perineal outcome at birth, results that indicate the belief that routine or prophylactic episiotomies will prevent long-term perineal muscle function decline is in error. Results would further suggest that episiotomy may actually contribute to a decline in postpartum perineal muscle function more than lacerations sustained spontaneously. These findings indicate that perineal management strategies should be based on factors other than an attempt to preserve or promote long-term perineal muscle function. If indeed episiotomies contribute to a comparative decrease in perineal muscle function, then the procedure should be reserved for other obstetric indications.


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