Effectiveness of transcutaneous electrical nerve stimulation for painful postpartum uterine contraction during brestfeeding

INTERVENTION: Transcutaneous electrical nerve stimulation (TENS) ‐ frequency of 80 Hz, pulse duration of 100 microseconds and intensity adjusted by the participant as strong and tolerable, producing a tingling sensation. This intervention happens once every participant in the TENS group, for a continuous period of 40 minutes during breastfeeding. CONDITION: painful uterine contraction PRIMARY OUTCOME: Primary outcome 1: 2‐point reduction in pain scores by the numeric rating scale after use of TENS. SECONDARY OUTCOME: Secondary outcomes 1: satisfaction with TENS treatment through a questionnaire of satisfaction (very satisfied, satisfied, little satisfied, unsatisfied). Secondary outcomes 2: use of TENS in the next brestfeedings through a questionnarie (yes ou no). Secondary outcomes 3: discomfort produced by TENS through a questionnaire of discomfort (no discomfort, mild discomfort, moderate discomfort, severe discomfort, discomfort worst possible). INCLUSION CRITERIA: The inclusion criteria of the research are: women after vaginal delivery, multiparity, without complications postpartum, pain level greater than "one" by Numeric Rating Scale Pain, literate, capable of understanding the pain scales used and follow the procedures of motherhood.