Transcutaneous electrical nerve stimulation (TENS) is a non-invasive electro-physical modality used for several pain conditions including labor pain control. Despite several years of research, there is still no agreement within the literature regarding the selection of TENS parameters. It is aimed to investigate two types of TENS frequencies (TENS1 alternating between 4 to 100 Hz and TENS2 alternating between 80 to 100 Hz) compared to sham-TENS.

Midwives and the study investigator will ask parturients, who are admitted to the labor ward at Region Hospital Herning satisfying the inclusion and exclusion criteria, whether they are interested in attending the experimental session.

The study will be conducted as soon as the subject is admitted at the labor ward. The study will only be conducted during early and active labor and not during the birth of the baby.

The subject in this study includes the package of a parturient and her neonate (after birth) as we also obtain data about the neonate. Hereby, two consent forms will be obtained. As this study is a non-invasive study, it is decided to have at least the consent of one parent.

The investigator will fill out a questionnaire about the parturient in cooperation with the subject and midwife, including screening questions related to inclusion and exclusion criteria before the experimental session starts.

The study will last approximately one hour and will be conducted during laboring circumstances. KT (Kenoja Thuvarakan) will carry out the experiment, and she will be present in the delivery room during the whole session.

The study includes several outcomes, including subjective and semi-objective pain measures. The primary outcome is VAS (0-10 cm scale), while secondary outcomes include PPT and satisfaction questionnaire (only at the end of the study). The subjects will be asked before, and immediately after the experimental exposure about the four outcomes (VAS and PPT). The subjects will be exposed to one of the two combinations of TENS stimulation (low and high alternating frequency), which will be compared to sham-TENS.

Inclusion Criteria:

• Singleton pregnancy
• Between ages 18-39 years
• Vertex presentation
• Speak, read and understand Danish
• At term (37-42 weeks gestation age)

Exclusion Criteria:

• High-risk pregnancies (including risk factors: eclampsia, pre-eclampsia, diabetes, gestational diabetes, hypertension, and hypotension, intrauterine growth restriction, polyhydramnios, and oligohydramnios).
• Pre-gestational body mass index above 40 kg/m2
• Use of fetal-scalp electrode during the experiment
• Use of pacemakers and other electronic implants
• Severe arrhythmia
• Present musculoskeletal/neurological illnesses
• Chronic pain within last 6 months
• Present medicated mental disorders
• Dermatological disorders
• Use of other long-acting pain relief
• Use of TENS 48 hours before the trial
• Drug addiction defines as the use of cannabis, opioids, or other drugs.
• Smokers
• Lack of ability to cooperate

Individual participant data is described in Danish and therefore no plan of sharing.

Double-blinded