What Actually Happens to Your Pelvic Floor Muscles During Labor?

Childbirth is a Herculean feat, pushing your body to its limits—especially your pelvic floor muscles. These important muscles stretch to about 3 times their normal length during vaginal delivery. To get an idea of the level of stretch we're talking about, grab a 4-inch rubber band and see what happens when you stretch it to 12 inches.

The impact of childbirth on your pelvic floor and overall pelvic health is significant and not talked about enough. According to the 2024 Origin Pelvic Health Study, 83% of women ages 18 to 59 experienced at least one pelvic health symptom in the past year, with even higher rates for those who have had a baby.

The consequences of pelvic floor injury during childbirth can be “life-altering” with nearly 1 in 10 women who give birth vaginally eventually requiring surgery due to a pelvic floor disorder. These injuries can lead to distressing lifelong consequences and affecting quality of life. Despite this prevalence, 96% of women with symptoms have not been diagnosed with a related medical condition.

On the bright side: Empowering birthing people to take care of their pelvic health before and after childbirth can lead to better outcomes, especially since most pelvic floor injuries are preventable or treatable with pelvic floor PT.

To help you feel more empowered, let's talk about what happens to your pelvic floor muscles during labor and childbirth.

Q: What happens to the pelvic floor muscles during labor?

A: During childbirth, pelvic floor muscles are stretched significantly, often more than three times their normal length. Researchers used conceptual models to better understand what happens to the pelvic floor during g vaginal birth. Here are some of the things they found:

1. The pelvic floor muscles undergo extreme stretching, with portions stretching to more than 3 times their normal length by the end of the second stage of labor (when the baby’s head is crowning).
2. Forceps use increases levator ani muscle injury risk due to additional traction on already strained muscles. (Check out your levator ani muscles in this pelvic floor diagram.)
3. Even without forceps, pelvic floor muscles stretch beyond what's considered safe for typical skeletal muscles in the non-pregnant person.
4. Pelvic floor nerves, especially those to the anal sphincter, stretch beyond their damage threshold, risking injury.

This extreme stretching affects both muscles and nerves, potentially leading to various pelvic floor issues postpartum.

Q: Which pelvic floor muscle is most at risk for injury during childbirth?

A: The entire levator ani muscle group is vulnerable to injury during childbirth, as these are the muscles that surround and support the vagina and pelvic organs.

The pubococcygeus muscle, which is the short levator ani muscle and innermost muscle to wrap around the vagina, was shown to stretch to 3.3 times its resting length, and was said to be the muscle most at risk for stretch injury during a vaginal birth.

Q: How does labor and birth effect the pelvic floor?

A: Childbirth can have significant impacts on your pelvic floor:

• Muscle injury: Stretching and straining can cause tears or avulsion of pelvic floor muscles and connective tissues.
• Nerve damage: Stretching can lead to neuropathy, affecting long-term pelvic floor function. One study found nerve injury evidence in 25% of women 6 weeks post-delivery.
• Pelvic floor disorders: Injury may result in developing signs and symptoms of pelvic floor dysfunction including bowel and bladder leakage, pelvic, vaginal, and/or vulvar pain, pelvic organ prolapse, and sexual dysfunction. In fact, a recent multi-center prospective study found that nearly 1 in 3 women reported symptoms of a pelvic floor disorder in the postpartum.

These effects can vary depending on factors like the duration of labor, mode of delivery, and your individual anatomy.

Q: Do pelvic floor muscles push the baby out?

A: Contrary to popular belief, your pelvic floor muscles don’t actively push your baby out. During the second stage of labor (aka the pushing phase) your uterus and your abdominal muscles (from your pishing efforts) are the true pushing heroes.

Instead, your pelvic floor muscles are meant to lengthen and stretch to allow your baby to move down your birth canal (your vagina). In other words, they should be trying to get out of the way.

Q: What is pelvic floor trauma in childbirth?

A: Pelvic floor trauma in childbirth refers to injuries sustained by the pelvic floor muscles, nerves, and connective tissues during vaginal birth. This can include:

• Muscle tears or avulsions
• Nerve damage
• Stretching of ligaments and fascia
• Perineal tears
• Anal sphincter injuries

These injuries can lead to various pelvic floor disorders postpartum.

Q: Does childbirth weaken the pelvic floor muscles?

A: The extreme stretching of pelvic floor muscles during childbirth may lead to weakened support and increased risk of pelvic organ prolapse later in life. However, research findings are mixed.

A recent meta-analysis suggests vaginal birth may double the prevalence of pelvic floor disorders compared to cesarean births. Another large study found a reduced risk of pelvic floor disorders with cesarean deliveries. Conversely, one review found no difference in short-term pelvic floor muscle strength between vaginal and cesarean births.

While more research is needed, the good news is that pelvic floor muscle weakness can often be improved with proper postpartum rehabilitation and exercises.

Q: How do pelvic floor muscles interact with the fetal head during labor?

A: During labor, the pelvic floor muscles which surround the vagina come into contact with the fetal head (through the vagina wall). As labor progresses, these muscles stretch and thin out to allow for the descending head. Experts say that this interaction is crucial for the proper positioning and rotation of the fetus as it moves through the birth canal. These movements are known as cardinal movements, and it is thought that resistance from the pelvic floor muscles helps the fetal head to flex (so their chin ticks toward the more chest), so it can be in optimal position for birth.

Q: How do you relax your pelvic floor muscles and not tense up for birth?

A: Relaxing your pelvic floor muscles for birth can be achieved through various techniques:

1. Practice deep breathing exercises
2. Use visualization techniques to imagine your pelvic floor opening and relaxing
3. Try perineal massage in the weeks leading up to birth
4. Consider using warm compresses during labor
5. Considered upright or squatting positions during labor, which can help naturally put pressure one the pelvic floor to help lengthen it.
6. Practice relaxation techniques like progressive muscle relaxation or mindfulness
7. Use rhythmic breathing patterns and practice different pushing techniques beforehand.

Just because you give birth to a baby does mean you're destined to deal with pelvic health issues! Reach out to a physical therapist here at Origin for personalized education and treatment during pregnancy and postpartum. Our experts can help you build pelvic floor (and whole body) strength, flexibility, and muscle control to get you ready for childbirth, practice labor positions, and ensure optimal pelvic floor health post-delivery.