In February's blog, “Pelvic Floor Birth Injuries: What does the research say?”, we learned that obstructed labor leading to either prolonged second stage, need for fundal pressure, or need for instrumental delivery, particularly forceps, substantially increases the risk of both OASI (obstetric anal sphincter injury) and levator avulsion.
Besides dealing with perineal pain during the first few weeks of recovery, OASI is also associated with an increased risk of fecal incontinence and pelvic organ prolapse, and there is a very strong correlation between OASI and levator ani (a deep pelvic floor muscle) injury.
Women are not routinely informed of these risks even though studies have suggested that women want to know their risk of developing pelvic floor dysfunction to help make decisions about child birth and to motivate them to seek out preventative strategies such as Pelvic Floor Physical Therapy.
Which brought on the question, does prenatal pelvic floor function influence who might be more at risk of an obstructed labor? Let’s discuss what the research has said so far.
Levator Hiatus Size
The levator hiatus area is a measurement that is commonly referred to in pelvic floor research and labor and birth outcomes. The levator hiatus is an opening in the pelvic floor allowing the passage of the urethra, rectum, and the vagina (and baby during a vaginal birth!) and is bordered on either side by the levator ani muscles, as highlighted in green. This measurement is typically obtained via 2D or 3D ultrasound.
During a vaginal birth, the levator ani muscles can stretch up to 3 times their resting length as the baby’s head is crowning. Research has shown that the size of the levator hiatus can have an impact on labor outcomes. A smaller the levator hiatus is associated with:
A longer the second stage (or pushing phase) of labor
A smaller chance of having a normal vaginal delivery (without the use of instruments such as vacuum or forceps)
An increased risk of levator ani muscle avulsion injury (occurs when there is a disconnection of the levator ani muscle from its attachment onto the pubic bone)
Perhaps levator hiatus measurements should be incorporated into current screening procedures during pregnancy to help identify who could be at an increased risk of obstructed labor and monitored accordingly?
Pelvic Floor Function
During the second stage of labor, women are actively pushing or bearing down.
The pelvic floor should be relaxing and not contracting when pushing or bearing down. Pelvic floor co-contraction or co-activation is the inability to appropriately coordinate the relaxation of the pelvic floor with bearing down, and instead we see pelvic floor muscle contraction. A pelvic floor muscle contraction causes the levator hiatus to decrease in size, whereas pelvic floor relaxation allows the levator hiatus to increase in size.
The presence of pelvic floor co-activation with bearing down is associated with
A longer the second stage (or pushing phase) of labor
An increased risk of operative delivery (use of instruments such as vacuum or forceps)
Less engagement of the fetal head
As pelvic floor co-activation is recognizable prior to birth, there may be an opportunity to help women improve the coordination of pelvic floor relaxation prior to the onset of labor. Enter…Pelvic Floor Therapists!!!
Pelvic Floor Muscle Training
As stated above, pelvic floor dimensions and proper pelvic floor relaxation seem to play a key role in childbirth. So the question is, can we achieve better labor outcomes by improving pelvic floor function with pelvic floor muscle training? I wish we could give a more definitive answer, but the truth is, the research is still unclear.
Some studies suggested that pelvic floor muscle training reduces the duration of second stage of labor and rates of severe perineal tearing (OASI). Other studies suggest that it might not have made a difference. But of note, one definite fact is that not a single study has indicated that pelvic floor muscle training increases the duration of second stage of labor or worsens perineal tearing - it either improves it or does not make a difference. So truly, we need more quality research to definitively say the impacts of pelvic floor muscle training on labor outcomes.
But are there other benefits to pelvic floor muscle training during pregnancy the research has identified? Spoiler alert…the answer is YES! You know what to do - stay tuned for our upcoming blog to learn more!
To start preparing in less than 2 hours, join Dr. Becca to learn how you can prepare for birth with simple tips on prenatal perineal massage, pelvic positioning during labor to minimize tearing, and how to advocate for your birth story. BONUS- Get moving again postpartum with our 6 week Mindful Movement Strategies!
Dr. Becca Jones, PT, DPT, CSCS, is a 2016 graduate of New York University with her Doctorate of Physical Therapy. Her passion for supporting people through their pregnancy and/or post partum journey inspired her to specialize in pelvic health. Dr. Becca believes in providing holistic, individualized care in order to restore comfort and build confidence to get people back to what they love.