BIRTH 18:3 September 1991
153
A Randomized Study of Two Methods of Teaching Perineal Massage: Effects on Practice Rates,
Episiotomy Rates, and Lacerations Pa tricia A. Myna ugh, Ph.D., R.N. ABSTRACT: This study examined the effects of two methods of teaching perineal massage on the rates of practice of perineal massage, of episiotomy, and of lacerations in primiparas at birth. Couples in 20 randomly selected sections of four prenatal class series received routine printed and verbal instruction and a 12-minute video demonstration of perineal massage, or only the routine printed and verbal instruction. Women reported theirpractice rates in daily diary records, which were mailed to the researcher weekly. Hospital records provided delivevy data. Of the 83 women, 23 (28%)practiced perineal massage: 16 (35.6%) in the experimental group, 7 (18.4%) controls. Even though the rate of practice almost doubled among experimental group women, the videotape instruction method was statistically nonsignijkant. Episiotomy and laceration rates were not affected by teaching method. More severe lacerations occurred among the experimental group; however, the control group had almost four times as many severe (21%) as minor (5.3%) lacerations. The experimental group had twice as many severe (28.9%) as minor (13.3%) lacerations. These results were also nonsigngicant. (BIRTH 18:3, September 1991)
Episiotomy is the most common operation in obstetric practice today in the United States, being performed in 57 percent of all vaginal deliveries (I). One text recommended it for all primiparas age 35 years or older (2). From the time Ould (3) first mentioned it over two centuries ago, discussions have centered on the types of incisions, suturing methods and materials, and the supposed benefits of episiotomy, but rarely on whether or not it should be a part of present-day practice (4). Negative results of episiotomy include pain, which may persist for up to three months after delivery (5,6) or longer (7), and was reported to be greater immediately after delivery than that from a second-degree laceration (7,8).Women have also experienced difficulty performing activities of daily living. Maternal deaths resulted from infected inci-
Patricia A . Mynaugh is Assistant Professor of Nursing at the College of Nursing, Villanova University, Villanova, Pennsyfvania. Address correspondence to the author, College of Nursing, Villanova University, Villanova, PA 19085.
sions (9-11),as did injuries to infants (12,13). In addition, episiotomy increased the frequency of third- and fourth-degree lacerations (14,15). Episiotomy rates decreased when attempts were made to deliver women without surgical intervention. In the study by Harrison et al. (8), primigravidas were randomly allocated to one of two groups. Of the 92 women allocated not to undergo an episiotomy, 7 (8%) had one, compared with 507 (89%) in the previous six months, on whom the procedure was performed routinely. A randomized, controlled trial compared 1000 primiparas and multiparas using two different policies for perineal management in spontaneous vaginal deliveries (16).When episiotomy was restricted to fetal indications, frequency was 10.2 percent, which was lower than the 51.4 percent when episiotomy was performed to prevent perineal tears. The rates for primiparas were 17.9 percent in the restricted use group and 67.1 percent in the liberal use group. Three years later the follow-up study demonstrated that liberal use of episiotomy did not appear to prevent urinary incontinence or increase dyspareunia ( 17).
BIRTH 18:3 September 1991
154 A randomized, controlled study of 182 primiparas and multiparas also was divided into two perineal management strategies: “try to avoid an episiotomy” (restricted) and “try to avoid a tear” (liberal) (IS). Overall, the episiotomy rates were 54.1 percent for the latter and 36.8 percent for the former. In primiparas the rate decreased from 65.3 to 42.9 percent when attempts were made to avoid a tear versus avoid an episiotomy, respectively. Several studies reported that perineal massage practiced for five minutes daily during the last six weeks of pregnancy may condition perineal tissue, increase tissue elasticity, and reduce the need for episiotomy and frequency of laceration during vaginal birth (19-22). A prospective, randomized study compared five nulliparous and five parous women in the experimental group who practiced perineal massage with similar control subjects. matching for maternal age, parity, fetal weight, and gestational age (19). Frequency of episiotomy and laceration in the massage group (10%) was much less than that in the control group (80%). All women were delivered by nurse-midwives. In a nurse-midwifery practice in which perineal massage is encouraged prenatally, as well as a slow, controlled delivery of the fetal head, of 1858 deliveries the rates of episiotomy, lacerations, and intact perinea were 27,36, and 37 percent, respectively (22). Video use in patient instruction has increased. Gagliano (23) reviewed the literature on video efficacy in patient education. Conclusions were based on 25 studies, most of which were randomized, controlled clinical trials. The effects of video education on short-term knowledge were equal to or better than those of traditional methods, but equal to or worse than those of traditional methods on longterm knowledge. Behavioral changes occurred in a short time period, but long-term compliance appeared to be influenced by other factors such as emotional needs. This study investigated women’s prenatal rates of perineal massage practice after two different instruction methods given in childbirth education classes. The effects of video education on episiotomy and lacerations were also assessed.
tal classes, and independently pursued enrollment and choice for night of class attendance.
Class Randomization Four class groups met during the study period, each of which was subdivided into smaller sections by the course coordinator, for a total of 20 sections (Table 1). Each section was taught for two hours, one night per week for seven weeks. All sections were randomly assigned by coin toss to a combination of printed and verbal instruction in perineal massage (control group), or to this routine instruction plus a video demonstration (experimental group). A total of 83 women (45 experimental, 38 control) participated. Sample
The research project was described by the author to I88 women during their second prenatal class visit. If they agreed to participate, they completed a demographic data sheet, planned t o keep daily records, permitted collection of delivery data from their hospital records, and completed a questionnaire approximately 10 weeks after delivery. On signing the hospital consent form and completing the baseline data sheet, they were told about the planned follow-up visit during their classes. One hundred fifty women agreed to participate, and 67 women were dropped from the study, leaving 83. The 67 women who did not meet the study protocol included 39 who had cesarean births, 8 who had previous children, 2 who delivered elsewhere, 3 who delivered prematurely, and 1 whose fetus died. Other losses included 8 who refused consent or withdrew and 6 who delivered before massage could be done. Table 2 shows demographic characteristics of the two groups. The only statistical difference between Table 1. Class Randomization
Class
Number o j Women
1
Methods
2 experimental 2 control
11
2 experimental 2 control
8
2 experimental
3 control
8 10
3 experimental 4 control
18 16
6
2
The study was conducted from June 22, 1987, through February 27, 1988. The sample comprised healthy primiparas at 25 to 36 weeks’ gestation who anticipated uncomplicated vaginal delivery by physicians at a 7 17-bed, tertiary-care university hospital in a large East Coast city. Couples received information from their obstetrician concerning prena-
6
3
4
155
BIRTH 18:3 September 1991
Table 2. Demographic Characteristics ~~
Sociodemographic Variables
Experimental No. (%) (n = 45)
Mean age (yrs)
27.7
Race Black, Hispanic White Education G High school Businesdvocationalhorne college 3 Coliege/post college Income > $30,000
Control No. (%) (n = 38)
30.1
8 (17.8) 37 (82.2)
2 (5.3) 36 (94.7)
8 (17.8) 11 (24.4) 26 (57.8) 38 (86.4)t
7 (18.4) 13 (34.2) 18 (47.4) 31 (88.6)1:
Statistical Analyses
T = 2.33 P = 0.023*
x2 = 3.045 P = 0.08 x2 = P
=
1.105 0.575
x2 = 0.806 P
=
0.66
* Statistical sign$cance between groups for age. i. One woman did not answer this question. it Three women did no1 answer this question.
them was for age ( P = 0.023), which was attributed to the study design because the women self-selected their class night. Obstetricians were informed about the study, and their permission was requested for their patients to participate. They did not know to which group patients were assigned. Instruments The 12-minute video instruction tape, developed by the author, depicted the anatomy of the perineum, described an episiotomy, and demonstrated perinea1 massage on an obstetric manikin. The author showed the video during the prenatal class, during which perineal massage was discussed by the instructor. After the video, the author again described the frequency of episiotomy and how massage practice can soften and stretch the perineal tissue to prevent episiotomy and lacerations. Couples’ questions were answered. A written handout on perineal massage, with instructions, was in an informational packet given by instructors to all couples at the first class. Generally, the instructors stated that episiotomy was done to prevent tears, described perineal massage, referred couples to the printed instructions, and answered questions. The printed instructions covered hand washing; lubricating the thumbs or fingers with a vitamin E, vegetable oil, or water-soluble jelly; taking a semisitting position with back support; inserting both thumbs into the vagina up to the second knuckle (partner using both index fingers); and moving the thumbs (or partner’s fingers) down and along the vaginal wall in a rhythmic or sling movement. They described rubbing or massaging the perineal skin
between two digits by using the thumb (or partner’s finger) inside the vagina and the index finger of the same hand (or partner’s thumb) outside. Five minutes was the recommended time for the whole procedure. All couples were warned that if vaginitis, herpes, or other vaginal problems existed, massage might worsen the condition(s), and they should seek a physician’s help. Massage teaching was incorporated into class content in June 1985 as part of the standard childbirth education. Although ideally it should have been confined to the randomly chosen experimental sections to detect its effects, the university’s Institutional Review Board emphasized that if perineal massage were withheld from one-half of the couples, they should be informed that they were not receiving the approved standard education in the classes. Since this statement had the potential to decrease women’s willingness to be recruited and thus restrict the number of study participants, all sections received the usual printed and verbal instructions; 9 of the 20 sections also viewed the video and were taught by the author. Statistical Analysis
Using chi-square analysis, statistical significance was set (P < 0.05). With that and with 1 and 2 degrees of freedom, there was a 67 to 76 percent chance of detecting a 0.30 change with 83 participants; 100 to 140 participants would be required to increase the power to 85 to 90 percent for a 0.30 change at P < 0.05 with 1 and 2 degrees of freedom; and 200 to 350 for 0.20 reduction at 81 to 93 power with P < 0.05 with 1 and 2 degrees of freedom (24). Generally, a study should have a power of 0.80 or greater to detect a reasonable effect size ( 2 9 , if one
BIRTH 18:3 September 1991
156
exists, Power was chosen to improve the interpretation of data rather than to look only for statistical significance of results (26). Odds ratio and confidence intervals were used to augment findings. The odds ratio is an expression of the comparison of the odds of the outcomes in the experimental group with the odds in the control group (27). The 95 percent confidence interval ensures that 95 percent of the samples selected with this study population will fall within that interval. If the confidence interval does not include 1, a difference has been detected between the interventions tested, and the null hypothesis has therefore been rejected. Results Effect on Practice Rates
Twenty-three women (28%) (16 experimental; 7 control) practiced perineal massage. The type of instruction did not statistically influence the practice rate. Practice rates almost doubled in the experimental group, but were not statistically significant (P = 0.08) (Table 3). The hypothesis was that 30 percent more women in the video group would practice perineal massage than those in the printed and verbally instructed group. Avery's study (20) began with 92 experimental group women and ended with 29. Subjects were dropped for stopping massage and for factors associated with labor or delivery. All study women massaged, even though this number (29) represented approximately one-third of the original experimental group number (92). Recognizing that one-third of that study's women remained for analysis, I hoped to achieve an increase in massage practice of 30 percent above the verbally instructed group, given that women were excluded only for the previously mentioned reasons. I obtained only a 17.2 percent increase. A sample of 90 participants would be required using alpha at P < 0.05, with a power of 0.81 for a 0.30 difference. These study results show the odds ratio
(95% confidence interval) is 2.44 (0.79-7.73). Table 4 shows results between experimental and control group women. Ejfect on Episiotomy Rates
Both experimental and control group women had high episiotomy rates, 84.4 and 89.5 percent, respectively. When Sleep et al (16) restricted episiotomy to fetal indications in primiparas, the rate was 17.9 percent, a reduction of 49.2 percent from 67.1 percent when it was performed to prevent perineal tears. A 20 percent reduction in episiotomy rate with the video group was the hoped-for result, using the 17.9 percent reduction above. This did not occur, since a 20 percent decrease would have needed 200 women using alpha at P < 0.05, with power of 0.81. The results show the odds ratio for this study (95% confidence interval) is 0.64 (0.14-2.74). Video instruction did not lower the episiotomy rate. Eflect on Lacerations
When Sleep et al. (16) attempted to avoid lacerations versus avoid an episiotomy, a 32.9 percent reduction was achieved between the two groups of primiparas. The present study showed a higher laceration rate in the experimental group than in the control group. I hypothesized that there would be a 30 percent reduction in the laceration rate in the videoinstructed group than in the verbally instructed group. There was a 15.9 percent increase. I would have needed a sample size of 90 participants with alpha at P < 0.05, with a power of 0.81. Results show the odds ratio (95% confidence interval) is 2.05 (0.73-5.80). There was no statistical significance ( P = 0.13). Video instruction did not lower the laceration rate. First-degree (extending through skin and superficial tissues) and second-degree (extending through perineal muscles) perineal lacerations were combined with external tears (periurethral and labial
Table 3. Massage Practice Rates Experimental No. (%) Pructice
(n
=
45)
Control No. (%)
(n
= 38)
Odds Ratio Chi-square
df
P
(95% CZ)
3.019
1
0.08
2.44 0.79-7.73
.-
~~
~
Massaged
16 (35.6)
7 (18.4)
Did not massage
29 (64.4)
31 (81.6)
Critical value of chi-square for 1 degree of freedom = 3.841. There was no statistical significance for massage practice with video instruction.
157
BIRTH 18:3 September 1991
Table 4. Perineal Effects Experimental N o . (%) (n = 45)
Control N o . (%) (n = 38)
Chi-square
df
P
Episiotomy, yes
38 (84.4)
34 (89.5)
0.453
1
0.50
Laceration, yes
19 (42.2)
10 (26.3)
2.293
1
0.13
Laceration severity None
26 (57.8)
28 (73.7)
2.693
2
0.26
0.66 0.211-2.01
2.318
2
0.31
0.64 0.142.74
Perineal Effects
Minor Severe Perineum Episiotomy only
6 (13.3) 13 (28.9)
2 (5.3) 8 (21.0)
26 (57.8)
28 (73.7)
Episiotomy and extensions Lacerations only
12 (26.7) 7 (15.5)
6 (15.8) 4 (10.5)
Critical value of chi-square for I degree of freedom = 3.841 and for 2 degrees of freedom All P values are not statisticatty significant.
tears) and grouped together as minor lacerations. The serious lacerations were classified as thirddegree (severing the rectal sphincter) and fourthdegree (tearing the anterior rectal wall), and included vaginal and cervical tears. Any woman with more than two lacerations was placed in the serious laceration category. Sleep et al. (16) reported a 0.8 percent severe trauma rate in the group allocated to avoid an episiotomy, and 0.1 percent in the group allocated to avoid a tear. I hypothesized a 30 percent reduction between severe and minor lacerations, and would have needed 90 to 120 participants for 0.81 to 0.85 power at P < 0.05 with 1 and 2 degrees of freedom. These results showed a 15.6 percent reduction between severe and minor lacerations in the experimental group. Although more severe lacerations occurred among the experimental group (28.9%) than the control group (21%), the latter had almost four times as many severe (21%) as minor (5.3%) lacerations, and the former had twice as many severe (28.9%) as minor (13.3%) lacerations. This was not statistically significant (P = 0.26). Results show the odds ratio (95% confidence interval) is 0.66 (0.2112.01). Effect on Extensions from Episiotomies
In the study by Sleep et al. (16) the extension rate was 2 percent when episiotomy was restricted to fetal indications and I0 percent when done to avoid perineal tears. If I aimed for a 10 percent reduction
=
Odds Ratio (95% CI) 0.64 0.142.74 2.05 0.73-5.80
5.991.
in extensions, 800 to 1000 women would be needed at alpha P < 0.05, for a power of 0.81 to 0.82 with 1 and 2 degrees of freedom. Extensions occurred more with the experimental group (26.7%) than with the control group (15.8%), but these results were not statistically significant (P = 0.31). The odds ratio (95% confidence interval) is 0.64 (0.14-2.74). Effect on Infants
No problems from episiotomy were reported with the infants in this study. Controlling for infant birthweight (
153
A Randomized Study of Two Methods of Teaching Perineal Massage: Effects on Practice Rates,
Episiotomy Rates, and Lacerations Pa tricia A. Myna ugh, Ph.D., R.N. ABSTRACT: This study examined the effects of two methods of teaching perineal massage on the rates of practice of perineal massage, of episiotomy, and of lacerations in primiparas at birth. Couples in 20 randomly selected sections of four prenatal class series received routine printed and verbal instruction and a 12-minute video demonstration of perineal massage, or only the routine printed and verbal instruction. Women reported theirpractice rates in daily diary records, which were mailed to the researcher weekly. Hospital records provided delivevy data. Of the 83 women, 23 (28%)practiced perineal massage: 16 (35.6%) in the experimental group, 7 (18.4%) controls. Even though the rate of practice almost doubled among experimental group women, the videotape instruction method was statistically nonsignijkant. Episiotomy and laceration rates were not affected by teaching method. More severe lacerations occurred among the experimental group; however, the control group had almost four times as many severe (21%) as minor (5.3%) lacerations. The experimental group had twice as many severe (28.9%) as minor (13.3%) lacerations. These results were also nonsigngicant. (BIRTH 18:3, September 1991)
Episiotomy is the most common operation in obstetric practice today in the United States, being performed in 57 percent of all vaginal deliveries (I). One text recommended it for all primiparas age 35 years or older (2). From the time Ould (3) first mentioned it over two centuries ago, discussions have centered on the types of incisions, suturing methods and materials, and the supposed benefits of episiotomy, but rarely on whether or not it should be a part of present-day practice (4). Negative results of episiotomy include pain, which may persist for up to three months after delivery (5,6) or longer (7), and was reported to be greater immediately after delivery than that from a second-degree laceration (7,8).Women have also experienced difficulty performing activities of daily living. Maternal deaths resulted from infected inci-
Patricia A . Mynaugh is Assistant Professor of Nursing at the College of Nursing, Villanova University, Villanova, Pennsyfvania. Address correspondence to the author, College of Nursing, Villanova University, Villanova, PA 19085.
sions (9-11),as did injuries to infants (12,13). In addition, episiotomy increased the frequency of third- and fourth-degree lacerations (14,15). Episiotomy rates decreased when attempts were made to deliver women without surgical intervention. In the study by Harrison et al. (8), primigravidas were randomly allocated to one of two groups. Of the 92 women allocated not to undergo an episiotomy, 7 (8%) had one, compared with 507 (89%) in the previous six months, on whom the procedure was performed routinely. A randomized, controlled trial compared 1000 primiparas and multiparas using two different policies for perineal management in spontaneous vaginal deliveries (16).When episiotomy was restricted to fetal indications, frequency was 10.2 percent, which was lower than the 51.4 percent when episiotomy was performed to prevent perineal tears. The rates for primiparas were 17.9 percent in the restricted use group and 67.1 percent in the liberal use group. Three years later the follow-up study demonstrated that liberal use of episiotomy did not appear to prevent urinary incontinence or increase dyspareunia ( 17).
BIRTH 18:3 September 1991
154 A randomized, controlled study of 182 primiparas and multiparas also was divided into two perineal management strategies: “try to avoid an episiotomy” (restricted) and “try to avoid a tear” (liberal) (IS). Overall, the episiotomy rates were 54.1 percent for the latter and 36.8 percent for the former. In primiparas the rate decreased from 65.3 to 42.9 percent when attempts were made to avoid a tear versus avoid an episiotomy, respectively. Several studies reported that perineal massage practiced for five minutes daily during the last six weeks of pregnancy may condition perineal tissue, increase tissue elasticity, and reduce the need for episiotomy and frequency of laceration during vaginal birth (19-22). A prospective, randomized study compared five nulliparous and five parous women in the experimental group who practiced perineal massage with similar control subjects. matching for maternal age, parity, fetal weight, and gestational age (19). Frequency of episiotomy and laceration in the massage group (10%) was much less than that in the control group (80%). All women were delivered by nurse-midwives. In a nurse-midwifery practice in which perineal massage is encouraged prenatally, as well as a slow, controlled delivery of the fetal head, of 1858 deliveries the rates of episiotomy, lacerations, and intact perinea were 27,36, and 37 percent, respectively (22). Video use in patient instruction has increased. Gagliano (23) reviewed the literature on video efficacy in patient education. Conclusions were based on 25 studies, most of which were randomized, controlled clinical trials. The effects of video education on short-term knowledge were equal to or better than those of traditional methods, but equal to or worse than those of traditional methods on longterm knowledge. Behavioral changes occurred in a short time period, but long-term compliance appeared to be influenced by other factors such as emotional needs. This study investigated women’s prenatal rates of perineal massage practice after two different instruction methods given in childbirth education classes. The effects of video education on episiotomy and lacerations were also assessed.
tal classes, and independently pursued enrollment and choice for night of class attendance.
Class Randomization Four class groups met during the study period, each of which was subdivided into smaller sections by the course coordinator, for a total of 20 sections (Table 1). Each section was taught for two hours, one night per week for seven weeks. All sections were randomly assigned by coin toss to a combination of printed and verbal instruction in perineal massage (control group), or to this routine instruction plus a video demonstration (experimental group). A total of 83 women (45 experimental, 38 control) participated. Sample
The research project was described by the author to I88 women during their second prenatal class visit. If they agreed to participate, they completed a demographic data sheet, planned t o keep daily records, permitted collection of delivery data from their hospital records, and completed a questionnaire approximately 10 weeks after delivery. On signing the hospital consent form and completing the baseline data sheet, they were told about the planned follow-up visit during their classes. One hundred fifty women agreed to participate, and 67 women were dropped from the study, leaving 83. The 67 women who did not meet the study protocol included 39 who had cesarean births, 8 who had previous children, 2 who delivered elsewhere, 3 who delivered prematurely, and 1 whose fetus died. Other losses included 8 who refused consent or withdrew and 6 who delivered before massage could be done. Table 2 shows demographic characteristics of the two groups. The only statistical difference between Table 1. Class Randomization
Class
Number o j Women
1
Methods
2 experimental 2 control
11
2 experimental 2 control
8
2 experimental
3 control
8 10
3 experimental 4 control
18 16
6
2
The study was conducted from June 22, 1987, through February 27, 1988. The sample comprised healthy primiparas at 25 to 36 weeks’ gestation who anticipated uncomplicated vaginal delivery by physicians at a 7 17-bed, tertiary-care university hospital in a large East Coast city. Couples received information from their obstetrician concerning prena-
6
3
4
155
BIRTH 18:3 September 1991
Table 2. Demographic Characteristics ~~
Sociodemographic Variables
Experimental No. (%) (n = 45)
Mean age (yrs)
27.7
Race Black, Hispanic White Education G High school Businesdvocationalhorne college 3 Coliege/post college Income > $30,000
Control No. (%) (n = 38)
30.1
8 (17.8) 37 (82.2)
2 (5.3) 36 (94.7)
8 (17.8) 11 (24.4) 26 (57.8) 38 (86.4)t
7 (18.4) 13 (34.2) 18 (47.4) 31 (88.6)1:
Statistical Analyses
T = 2.33 P = 0.023*
x2 = 3.045 P = 0.08 x2 = P
=
1.105 0.575
x2 = 0.806 P
=
0.66
* Statistical sign$cance between groups for age. i. One woman did not answer this question. it Three women did no1 answer this question.
them was for age ( P = 0.023), which was attributed to the study design because the women self-selected their class night. Obstetricians were informed about the study, and their permission was requested for their patients to participate. They did not know to which group patients were assigned. Instruments The 12-minute video instruction tape, developed by the author, depicted the anatomy of the perineum, described an episiotomy, and demonstrated perinea1 massage on an obstetric manikin. The author showed the video during the prenatal class, during which perineal massage was discussed by the instructor. After the video, the author again described the frequency of episiotomy and how massage practice can soften and stretch the perineal tissue to prevent episiotomy and lacerations. Couples’ questions were answered. A written handout on perineal massage, with instructions, was in an informational packet given by instructors to all couples at the first class. Generally, the instructors stated that episiotomy was done to prevent tears, described perineal massage, referred couples to the printed instructions, and answered questions. The printed instructions covered hand washing; lubricating the thumbs or fingers with a vitamin E, vegetable oil, or water-soluble jelly; taking a semisitting position with back support; inserting both thumbs into the vagina up to the second knuckle (partner using both index fingers); and moving the thumbs (or partner’s fingers) down and along the vaginal wall in a rhythmic or sling movement. They described rubbing or massaging the perineal skin
between two digits by using the thumb (or partner’s finger) inside the vagina and the index finger of the same hand (or partner’s thumb) outside. Five minutes was the recommended time for the whole procedure. All couples were warned that if vaginitis, herpes, or other vaginal problems existed, massage might worsen the condition(s), and they should seek a physician’s help. Massage teaching was incorporated into class content in June 1985 as part of the standard childbirth education. Although ideally it should have been confined to the randomly chosen experimental sections to detect its effects, the university’s Institutional Review Board emphasized that if perineal massage were withheld from one-half of the couples, they should be informed that they were not receiving the approved standard education in the classes. Since this statement had the potential to decrease women’s willingness to be recruited and thus restrict the number of study participants, all sections received the usual printed and verbal instructions; 9 of the 20 sections also viewed the video and were taught by the author. Statistical Analysis
Using chi-square analysis, statistical significance was set (P < 0.05). With that and with 1 and 2 degrees of freedom, there was a 67 to 76 percent chance of detecting a 0.30 change with 83 participants; 100 to 140 participants would be required to increase the power to 85 to 90 percent for a 0.30 change at P < 0.05 with 1 and 2 degrees of freedom; and 200 to 350 for 0.20 reduction at 81 to 93 power with P < 0.05 with 1 and 2 degrees of freedom (24). Generally, a study should have a power of 0.80 or greater to detect a reasonable effect size ( 2 9 , if one
BIRTH 18:3 September 1991
156
exists, Power was chosen to improve the interpretation of data rather than to look only for statistical significance of results (26). Odds ratio and confidence intervals were used to augment findings. The odds ratio is an expression of the comparison of the odds of the outcomes in the experimental group with the odds in the control group (27). The 95 percent confidence interval ensures that 95 percent of the samples selected with this study population will fall within that interval. If the confidence interval does not include 1, a difference has been detected between the interventions tested, and the null hypothesis has therefore been rejected. Results Effect on Practice Rates
Twenty-three women (28%) (16 experimental; 7 control) practiced perineal massage. The type of instruction did not statistically influence the practice rate. Practice rates almost doubled in the experimental group, but were not statistically significant (P = 0.08) (Table 3). The hypothesis was that 30 percent more women in the video group would practice perineal massage than those in the printed and verbally instructed group. Avery's study (20) began with 92 experimental group women and ended with 29. Subjects were dropped for stopping massage and for factors associated with labor or delivery. All study women massaged, even though this number (29) represented approximately one-third of the original experimental group number (92). Recognizing that one-third of that study's women remained for analysis, I hoped to achieve an increase in massage practice of 30 percent above the verbally instructed group, given that women were excluded only for the previously mentioned reasons. I obtained only a 17.2 percent increase. A sample of 90 participants would be required using alpha at P < 0.05, with a power of 0.81 for a 0.30 difference. These study results show the odds ratio
(95% confidence interval) is 2.44 (0.79-7.73). Table 4 shows results between experimental and control group women. Ejfect on Episiotomy Rates
Both experimental and control group women had high episiotomy rates, 84.4 and 89.5 percent, respectively. When Sleep et al (16) restricted episiotomy to fetal indications in primiparas, the rate was 17.9 percent, a reduction of 49.2 percent from 67.1 percent when it was performed to prevent perineal tears. A 20 percent reduction in episiotomy rate with the video group was the hoped-for result, using the 17.9 percent reduction above. This did not occur, since a 20 percent decrease would have needed 200 women using alpha at P < 0.05, with power of 0.81. The results show the odds ratio for this study (95% confidence interval) is 0.64 (0.14-2.74). Video instruction did not lower the episiotomy rate. Eflect on Lacerations
When Sleep et al. (16) attempted to avoid lacerations versus avoid an episiotomy, a 32.9 percent reduction was achieved between the two groups of primiparas. The present study showed a higher laceration rate in the experimental group than in the control group. I hypothesized that there would be a 30 percent reduction in the laceration rate in the videoinstructed group than in the verbally instructed group. There was a 15.9 percent increase. I would have needed a sample size of 90 participants with alpha at P < 0.05, with a power of 0.81. Results show the odds ratio (95% confidence interval) is 2.05 (0.73-5.80). There was no statistical significance ( P = 0.13). Video instruction did not lower the laceration rate. First-degree (extending through skin and superficial tissues) and second-degree (extending through perineal muscles) perineal lacerations were combined with external tears (periurethral and labial
Table 3. Massage Practice Rates Experimental No. (%) Pructice
(n
=
45)
Control No. (%)
(n
= 38)
Odds Ratio Chi-square
df
P
(95% CZ)
3.019
1
0.08
2.44 0.79-7.73
.-
~~
~
Massaged
16 (35.6)
7 (18.4)
Did not massage
29 (64.4)
31 (81.6)
Critical value of chi-square for 1 degree of freedom = 3.841. There was no statistical significance for massage practice with video instruction.
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BIRTH 18:3 September 1991
Table 4. Perineal Effects Experimental N o . (%) (n = 45)
Control N o . (%) (n = 38)
Chi-square
df
P
Episiotomy, yes
38 (84.4)
34 (89.5)
0.453
1
0.50
Laceration, yes
19 (42.2)
10 (26.3)
2.293
1
0.13
Laceration severity None
26 (57.8)
28 (73.7)
2.693
2
0.26
0.66 0.211-2.01
2.318
2
0.31
0.64 0.142.74
Perineal Effects
Minor Severe Perineum Episiotomy only
6 (13.3) 13 (28.9)
2 (5.3) 8 (21.0)
26 (57.8)
28 (73.7)
Episiotomy and extensions Lacerations only
12 (26.7) 7 (15.5)
6 (15.8) 4 (10.5)
Critical value of chi-square for I degree of freedom = 3.841 and for 2 degrees of freedom All P values are not statisticatty significant.
tears) and grouped together as minor lacerations. The serious lacerations were classified as thirddegree (severing the rectal sphincter) and fourthdegree (tearing the anterior rectal wall), and included vaginal and cervical tears. Any woman with more than two lacerations was placed in the serious laceration category. Sleep et al. (16) reported a 0.8 percent severe trauma rate in the group allocated to avoid an episiotomy, and 0.1 percent in the group allocated to avoid a tear. I hypothesized a 30 percent reduction between severe and minor lacerations, and would have needed 90 to 120 participants for 0.81 to 0.85 power at P < 0.05 with 1 and 2 degrees of freedom. These results showed a 15.6 percent reduction between severe and minor lacerations in the experimental group. Although more severe lacerations occurred among the experimental group (28.9%) than the control group (21%), the latter had almost four times as many severe (21%) as minor (5.3%) lacerations, and the former had twice as many severe (28.9%) as minor (13.3%) lacerations. This was not statistically significant (P = 0.26). Results show the odds ratio (95% confidence interval) is 0.66 (0.2112.01). Effect on Extensions from Episiotomies
In the study by Sleep et al. (16) the extension rate was 2 percent when episiotomy was restricted to fetal indications and I0 percent when done to avoid perineal tears. If I aimed for a 10 percent reduction
=
Odds Ratio (95% CI) 0.64 0.142.74 2.05 0.73-5.80
5.991.
in extensions, 800 to 1000 women would be needed at alpha P < 0.05, for a power of 0.81 to 0.82 with 1 and 2 degrees of freedom. Extensions occurred more with the experimental group (26.7%) than with the control group (15.8%), but these results were not statistically significant (P = 0.31). The odds ratio (95% confidence interval) is 0.64 (0.14-2.74). Effect on Infants
No problems from episiotomy were reported with the infants in this study. Controlling for infant birthweight (
