The goal of this clinical trial is to test the efficacy of the perineal massage in reducing the levator ani muscle (LAM) co-activation. This phenomenon is characterized by the LAM contraction rather than its relaxation during the Valsalva maneuver and it is associated with adverse obstetric outcome. Participants who co-activate will be enrolled and randomized in 2 groups: group A, where women themselves perform the perineal massage during the third trimester of pregnancy and group B, where women undergo the standard care. Researchers will compare these groups to see if the perineal massage is able to reduce LAM co-activation.

The levator ani muscle has to relax instead of contracting during the pushing efforts in childbirth. However, some women consciously or unconsciously co-contract, or tighten, the levator ani muscle. This phenomenon is levator ani muscle co-activation. Recently, it has been shown that co-activation may be associated with unfavorable obstetric outcomes, such as prolonged second stages of labor and higher fetal head station in women with co-contraction.

Recently, a study assessing the correlation between levator ani muscle co-activation and perineal trauma has been published. This study found a significantly higher incidence of severe perineal trauma related to childbirth (i.e., third and fourth-degree lacerations and episiotomies) in women with levator ani muscle co-activation. This group of patients had approximately three times the risk of a vacuum-assisted vaginal delivery and five times the risk of developing a severe vagino-perineal laceration with potential involvement of the anal sphincter. Therefore, intervening in these patients with targeted measures to correct LAM co-activation in the third trimester of pregnancy might be promising.

Study design All women are informed about this study during the first trimester of pregnancy. During the anatomical scan, at 20-22 gestational weeks, women are screened for eligibility criteria, including: nulliparity, single pregnancy, fetus in cephalic presentation and fluency in Italian language. Women satisfying the inclusion criteria are asked to participate to this RCT. If women agree to participate in the study, an informed consent will be signed. Thereafter, a trans-perineal ultrasound will be performed in order to evaluate the presence of levator ani muscle co-activation. A medio-sagittal scan is obtained to identify the following landmarks: pubic symphysis, fetal head, rectum, and puborectal muscle. In this scan, the antero-posterior diameter of the anorectal angle (APD) is measured, which is the minimum distance between the postero-inferior border of the pubic symphysis and the anterior border of the puborectal muscle. This measurement is taken both at rest and during maternal pushing (Valsalva maneuver). Patients with co-activation will be identified by an APD during Valsalva that is smaller than the one observed at rest. Patients will be enrolled and randomized only in case of LAM co-activation.

A 1:1 randomization will be done using a specific function of Excel (preliminarily prepared by our Statistician). Women will be randomized in 2 arms: arm A is represented by the treatment "perineal massage", while arm B is represented by the "standard care".

At about 30 gestational weeks women randomized to arm A will be trained on how technically perform the perineal massage. Participants are instructed to do the perineal massage once daily from 34 gestational weeks until delivery, for at least 3 weeks continuously. By contrast, women randomized to arm B are informed on currently available recommendations to take care for pelvic floor in pregnancy. These recommendations include advices on healthy diet, physical activity and voiding training.

At 37-38 gestational weeks all randomized women are scanned again in order to measure the APD at rest and under Valsalva. All anthropometric and clinical data are collected and anonymized.

Intra-partum part of the study This part of the project involves data collection on labor, delivery, and neonatal outcomes. The labor and delivery care-providers operate blindly with respect to the antepartum ultrasound measurements.

The study was powered based on the primary endpoint, which is the 40% reduction in LAM co-activation at term after perineal massage therapy. It is necessary to randomize 58 subjects (29 women per group).

The primary outcome of this trial is to assess whether the intervention "perineal massage", compared to the standard care, is able to significantly reduce the levator ani co-activation. Secondary outcomes are the standardization of the perineal massage and the comparison of perineal trauma prevalence between the 2 arms.

Inclusion Criteria: pregnant women with the following characteristics:

• nulliparous
• single pregnancy
• cephalic presentation of the fetus
• Italian language fluency

Exclusion Criteria:

• multiparous
• age < 18 y, age > 40 y
• previous urinary or fecal incontinence
• contraindications to vaginal delivery (such as placenta previa, vasa previa, etc)
• twin pregnancy
• language barrier
• BMI at or > 30

All of the individual participant data collected during the trial, after deidentification.

immediately after publication

to gain access data requestors should contact the principal investigator: Serena Xodo, e-mail: serena.xodo@gmail.com