Effect of pregnancy and childbirth on perineal musculature in women with obesity. A longitudinal cohort study.

Objective: Evaluating the changes of the perineal muscles in primigravid women with obesity (BMI ≥ 30) and to compare the progress with primigravid women in normal BMI range.

Methods: A prospective longitudinal cohort study was carried out. The pregnant women were studied at three moments: at 12 weeks' gestation, at 34 weeks' gestation and at 12 weeks after delivery. During the ckeck-up, perinometric measurements were taken to determine basal tone (BT), maximum contractile force (FMax) and applied forced (AF). In addition, the Oxford test (MOS) was used. General statistical mixed models were used for the statistical study.

Results: Fifty nulliparous pregnant women (25 with BMI ≥ 30 and 25 with BMI < 25) were recruited at the beginning of the study and 39 completed the entire study. Basal tone (BT) was 4.62 ± 0.24 Nw at the beginning of pregnancy and decreased to 4.18 ± 0.26 Nw after delivery. Contractile capacity was 5.56 ± 0.79 Nw at week 12 and increased to 6.34 ± 1.24 Nw after delivery. When comparing the FCMax at week 12 in obese VS normal weight pregnant women, values of 5.51 ± 87 Nw vs. 5.61 ± 0.71 Nw were observed (p = 0.941). Postpartum values were 6.72 ± 1.17 Nw vs 5.95 ± 1.21 Nw (p = 0.024), higher in the obese population.

Conclusions: There is an increase in contractile strength (Fmax) at 12 weeks postpartum in order to counteract the significant decrease in basal tone (BT). The body has compensatory mechanisms that allow recovery after 3 months postpartum, with greater muscle strength in obese patients.