Perineal Muscle Strength During Pregnancy and Postpartum: the Correlation Between Perineometry and Digital Vaginal Palpation

Endereço para correspondência: Maria Luiza Gonzalez Riesco Universidade de São Paulo. Escola de Enfermagem. Av. Dr. Enéas de Carvalho Aguiar, 419 Bairro Cerqueira César CEP: 05403-000 São Paulo, SP, Brasil E-mail: riesco@usp.br 1 Apoio financeiro da Fundação de Apoio à Pesquisa do Estado de São Paulo, processo no 07/00357-5. 2 Livre-docente, Professor Associado, Escola de Enfermagem, Universidade de São Paulo, SP, Brasil. E-mail: riesco@usp.br. 3 Doutor em Enfermagem, Professor, Centro Universitário Adventista de São Paulo, SP, Brasil. E-mail: acarocic@hotmail.com. 4 Livre docente, Professor Associado, Escola de Enfermagem, Universidade de São Paulo, SP, Brasil. E-mail: soniaju@usp.br. 5 Livre-docente, Professor Associado, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, SP, Brasil. E-mail: mhbaenaml@yahoo.com.br. Maria Luiza Gonzalez Riesco2 Adriana de Souza Caroci3 Sonia Maria Junqueira Vasconcellos de Oliveira4 Maria Helena Baena de Moraes Lopes5


Introduction
Damage caused to a woman's pelvic floor (PF) can lead to diminished or the loss of Pelvic Floor Muscle Strength (PFMS) and consequently to genital prolapse, fecal and urinary incontinence and constipation.About one third of adult women have Urinary Incontinence (1)(2) (UI), which can impair a woman's physical, sexual, domestic, and professional and leisure activities (2)(3)(4) .
Altered PFMS has been the focus of studies and research due to the evolution of equipment and exams that make its evaluation and prognosis more precise (10) .
Studies evaluating PFMS through digital vaginal palpation and perineometry revealed that even though these are different methods, they are positively correlated (11,13) .Other authors, however, verified that there is no significant correlation between digital vaginal palpation and perineometry (15) .
The following question was investigated in this study: Can digital vaginal palpation be used to evaluate PFMS as an alternative to perineometry?
Therefore, this study verifies whether there is correlation between the two methods, perineometry and digital vaginal palpation, in PFMS evaluation in pregnant and postpartum women.

Method
This is a prospective cohort study addressing the evaluation of PFMS through perineometry and vaginal digital palpation.The population was composed of pregnant women who attended antenatal care in five Primary Care Units (PCU) and whose deliveries were performed in two hospitals in Itapecerica da Serra, SP, Brazil.The inclusion criteria were: being primigesta with up to 12 weeks of pregnancy.Exclusion criteria were: multiple pregnancies; abdominal or previous urogenital surgery; hormonal therapy; diseases that can interfere in PFMS; refusal of the women to allow digital vaginal palpation or the insertion of a perineometer into the vagina; difficulty in understanding the Portuguese language or communication difficulties.
The parameter adopted to calculate the sample size of women in the cohort study was the difference between the average PFMS evaluated in postpartum women who had cesarean section and vaginal delivery with perineal laceration (12) .An alternative formula was used to determine the sample in order to compare two averages when the groups have different sizes (16) .
A total of 136 pregnant women would be necessary to compose the cohort, assuming a probability of type one as being 5% and power of 80%.Because it is a longitudinal study with the possibility of dropouts, the number of participants was increased 50%, hence

Discussion
The variables analyzed to compare the dropout group and the studied sample indicated homogeneity between groups, which reduces the probability of bias due to the loss of cohort follow-up.
The PFMS values obtained through perineometry can be classified according to intensity: absence of contraction (0.0); mild contraction (1.6 to 16.0 mmHg); moderate contraction (17.6 to 32.0 mmHg); normal contraction (33.6 to 46.4 mmHg) (11) .The results of the three points of evaluation revealed that when the digital vaginal palpation was between grades 0 and 2, perineometry indicated mild contraction and when the digital vaginal palpation indicated grades 3 to 5, contraction was evaluated as moderate by perineometry.
The strong positive correlation obtained in this study between the two methods of evaluating PFMS indicates that perineometry can be validated by the clinical method of digital vaginal palpation using the Oxford scales, which is in agreement with other authors' conclusions (11,13) .
This correlation is important because in the absence of a perineometer, a specialized professional can perform evaluation through digital vaginal palpation (13) .
On the other hand, no significant correlation was found in a study carried out with 20 women using these same methods to evaluate PFMS.The article held that appropriate measurement of PFMS depended on the cooperation and position of the participants as well as the previous experience of the researcher, which hinder the evaluation task (15) .
We must take into account that even with technical standardization, randomization of the sequence of application of methods, previous instruction to women and PFMS measurements performed by the same professional, there were cases in which the Oxford scale indicated grades incompatible with values inferred by the perineometer.
The women participating in this study showed positive acceptance of the PFMS evaluation with both methods considering that, even though these are painless procedures, they may cause embarrassment and discomfort.It is worth noting that the evaluation was performed in the context of a antenatal consultation and postpartum return visit, situations in which a good rapport has been established between the researchers and participants.Of the total of women included in the study, 1.8% refused to continue the study.
It is important to stress that further studies addressing PFMS measurement are necessary to establish a profile of PFMS during pregnancy and puerperium.It is also essential that the professional caring for these women value not only the identification of factors related to reduced PFMS but also encourage them to practice exercises to strengthen the PF muscles and also to report complains related the genitourinary tract (6,9,(14)(15)17) .
Evaluating PFMS in the postpartum may serve as reference for guiding and preventing permanent Riesco MLG, Caroci AS, Oliveira SMJV, Lopes MHBM.
disorders or aggravation in the long term.Digital vaginal palpation is a simple method with no costs and does not require special equipment.However, it does require that the professional performing it to be appropriately trained to evaluate PFMS.This method has helped in the diagnosis of urinary, intestinal and sexual disorders.
A relevant methodological aspect in this study was the use of surface electromyography during the PFMS evaluation because women showed difficulty in distinguishing contractions of the pelvic floor and abdominal muscles.The use of this equipment avoided registering PFMS performed simultaneously with abdominal muscle contractions (18) .
Another important aspect of how data were collected to stress is that one researcher measured PFMS while another read the perineometry result.This sought to avoid the result of perineometry influencing the researcher while performing the digital vaginal palpation.
Several devices and evaluation methods and also a lack of standardized parameters to classify the pelvic floor function are observed in the literature, which limit comparison of results of different studies.Hence, this is a topic that warrants further investigation and debate.
In addition to issues related to PFMS evaluation, scientific literature also analyzes the impact of UI on women's emotional health -suffering, diminished selfesteem, isolation, difficulties coping with the problem, among others -which provides an important contribution to nursing practice in women's health (19) .

Conclusion
This study's results indicate that there is a positive correlation between the PFMS values obtained through perineometry and digital vaginal palpation, which indicates that both methods are valid measures of PFMS.
204 women needed to be recruited.Aiming to ensure the maximum number in the estimated sample, 226 pregnant women were included in the study.Data were collected between February 2007 and August 2008.The data collection form was exclusively developed for this study.The instrument and equipment used were previously tested and assistants were trained in the data collection technique.Data collection was carried out at three points in time: at the beginning of the pregnancy (up to 12 weeks), at the end of pregnancy (36 to 40 weeks) and during puerperium (42 to 60 days postpartum).Antenatal and puerperal consultations were carried out during data collection followed by the services' protocol.In the period of hospitalization for childbirth, one of the researchers visited the participants in the hospital and scheduled the return visit to the PCU to perform a postpartum evaluation.If any of the women missed the consultations, the researcher would visit them at home.The study was approved by the Research Ethics Committee (604/2006/CEP-EEUSP).The participation of the women was voluntary and they signed free and informed consent forms.Researchers have no agreements with the manufacturers or distributors of the equipment used in this study.Methods used to measure PFMS All the participants underwent two methods of PFMS measurement: perineometric (electronic perineometer) and digital vaginal palpation (Oxford scale).A table to randomly apply the sequence of PFMS measurement methods was used through a statistical program aiming to avoid biased data.The sequence cards were put in opaque envelopes opened only at the moment of the PFMS measurements.Hence, perineometry or vaginal digital palpation could be either the first or last measurement performed.Perineometry The electronic pressure perineometer model Perina 996-2  Quark was used.It registers the potential action of PF muscle contractions and translates their intensity to visual signs through a numerical scale graded from 0 to 46.4 mmHg.This device does not discriminate between pelvic floor and abdominal contractions.The chosen perineometer met all the requirements of the safety standard for electrometrical equipments and is registered in the Brazilian National Sanitary Surveillance Agency, Ministry of Health.Surface Electromyography To control abdominal relaxation during PFMS measurement, a surface electromyography model Bio-ADS1200  Lynx was used to detect, through external electrodes, electrical activity of the muscle during rest and contraction.It works with software linked Rev. Latino-Am.Enfermagem 2010 Nov-Dec;18(6):1138-44.www.eerp.usp.br/rlae

Table 1 -
Average values of perineometry (in mmHg) and digital vaginal palpation (Oxford scale grades) according to the point at which the evaluation was performed.Itapecerica da Serra, SP, Brazil.February 2007 to August 2008