Please welcome new Science & Sensibility contributor, Amanda Blaz, DPT. Amanda is a Physical Therapist in south central Montana and has recently completed her Certificate of Achievement in Pregnancy and Postpartum Physical Therapy (CAPP-OB) from the Section on Women's Health of the American Physical Therapy Association, one of 28 physical therapists in the country to do so. She will now be working toward that same certification in the area of pelvic floor rehabilitation. Amanda is also a DONA-certified birth doula. This is the first of a four-part series.

How Supine Positioning Became Commonplace
If you ask anyone in the United States to describe the appearance of a woman giving birth, a majority would likely describe the dorsal lithotomy position in which the mother is semi-recumbent with knees and hips flexed, all the while screaming and sweating. This is the most popularly portrayed childbirth image in television and movies, and the most common pushing position in the American labor and delivery world (65.9% of women deliver in this position) (Shorten '02). So it poses the question, if dorsal lithotomy is the most well-known and widely used position during second stage labor, is it the best?

Over the course of a four-part series I will look at the literature regarding the topic of second stage positioning, and offer a comparison of the dorsal lithotomy position vs. other non-supine positions, starting with the hands-and-knees position. In the next three posts, lateral lying, squatting and other alternate positions will also be discussed. While there are many differences in birth outcomes when comparing dorsal lithotomy to other second stage positions I will focus specifically on those related to the anatomy of the pelvis, pelvic floor musculature, orthopedic issues, and nerves of the pelvic and sacral areas.

Convenience vs. functionality
The position of the pelvis when in dorsal lithotomy places the birth canal at an angle that actually makes the baby travel upward. There are many texts and articles that cite this position as the 'gold standard,' suggesting that it is the most widely used and, therefore, the most satisfactory position for second stage. However, the reason dorsal lithotomy has long-been considered 'most satisfactory' is never delineated. In fact, many well-known books, such as Human Labor and Birthby Dr. Harry Oxorn, suggest that second stage dorsal lithotomy positioning is the favored position because it is easier for the attendant to access the birth canal and perineum, and take care of any complications that may arise. This doesn't necessarily prove the position as the most satisfactory for maternal outcomes.

Anatomical Concerns
When in the dorsal lithotomy position, a woman is putting direct pressure on her sacrum (tailbone), forcing it into a flexed position and making the pelvic outlet smaller. Also, as stated above, when in this position, the birth canal curve has an 'uphill' orientation, forcing the mother to have to push the baby against gravity through an increasingly narrowed space (flexed sacrum pushing into pelvic outlet space). Furthermore, it has been shown that the femoral nerve can be compressed at the inguinal ligament during delivery by thigh flexion, lateral hip rotation, and abduction (dorsal lithotomy position) (Sax 2006 ). Femoral nerve injuries can lead to quadriceps weakness and/or sensory loss to the front/middle part of the thigh. Weakness of the quadriceps can cause the knee to feel as though it is going to 'buckle' - increasing the woman's risk of an orthopedic injury. Functionally, quadriceps weakness can make it difficult for the mother to go up and down stairs or get in and out of a squat position - a position that is used frequently to care for or play with a young child. Lastly, dorsal lithotomy is a position to avoid when the following orthopedic issues are present during the pregnancy: sacroiliac joint dysfunction (common cause of low back pain in pregnancy), pelvic girdle pain, pubic symphysis dysfunction,coccydynia(painful tailbone), hip joint dysfunction, knee joint dysfunction. When these issues are present, the dorsal lithotomy position places a large amount of stress on these joints and can increase pain, discomfort, or may even further injure the affected area.

Take pubic symphysis separation for example:

If the mother already has a pregnancy-induced pubic symphysis separation (even a partial separation), placing her in the dorsal lithotomy position is going to further distract the joint because of the excessive hip abduction and external rotation required. Not only can this lead to excessive immediate postpartum pain, but prolonged supra-pubic pain and tenderness with radiation to the back or legs, difficulty walking, and occasionally, bladder dysfunction (Snow, 1997).

The Benefits of All-Fours
When a woman in is the quadruped (hands-and-knees) position, she has many advantages on her side: For one, the birth canal curve is in a downward orientation, allowing gravity to aid in descent of the baby - promoting a gentler passage rather than a forced upward journey that involves significantly greater pressures and level of effort for the mother. Secondly, the woman is able to sway side to side as well as flex and extend her spine to aid in pain/discomfort during and between contractions. Similarly, quadriped is a favorable position when sacroiliac joint dysfunction, pubic symphysis dysfunction, coccydynia, spondylolisthesis, discogenic pain, or spinal stenosis is present. This is due to the fact that joints are not placed in a position that places a large amount of compression or stress on them and can be easily adjusted by the mother to increase her comfort level. Also, when in this position, a woman is more amenable to manual prompting by birth attendants to contract abdominal musculature and relax/contract the pelvic floor to aid with pushing. Lastly, Soong (2002) showed that when giving birth in the quadruped position, a woman may have less need for perineal suturing when compared to the dorsal lithotomy position. With a sample size of 3,756 women who had a spontaneous vaginal delivery, 61% of those giving birth in the hands and knees position had intact perineums.

Although there are many advantages to delivering in the hands and knees position, there are also times when it is not advantageous. Obviously, it becomes a less likely option when an epidural has been placed (depending on analgesic used and flow rate). Secondly, some women may not be able to maintain this position because of decreased mobility, decreased core strength, increased fatigue, or other factors. Lastly, this position is not favorable if the woman has any knee joint dysfunction as it requires weight bearing on the joint and at least 90° of knee flexion.

Current literature supports the fact that non-supine positions are most often favorable when compared to the dorsal lithotomy position. It has been found in many articles that women who delivered in a non-supine position tended to experience easier pushing, less pain with pushing, less back pain, and fewer perineal tears which leads to reduced need for suturing (Gardosi, 1989, Liddell 1985). I feel that because of these favorable outcomes, it should be at the forefront of our pregnancy and inter-partum community to educate women on the options they have as far as positioning during the second stage is concerned. Maybe one day we will see a baby delivered in a movie while the woman is on her hands and knees.

References:

Gardosi, J., Sylvester, S. and B-Lynch, C. (1989), Alternative positions in the second stage of labour: a randomized controlled trial. BJOG: An International Journal of Obstetrics & Gynaecology, 96: 1290-1296.

Liddell, H. S. and Fisher, P. R. (1985), The Birthing Chair in the Second Stage of Labour. Australian and New Zealand Journal of Obstetrics and Gynaecology, 25: 65-68

Sax TW, Rosenbaum RB. Neuromuscular disorders in pregnancy. Muscle Nerve. 2006 Nov; 34(5):559-71

Shorten, A., Donsante, J. and Shorten, B. (2002), Birth Position, Accoucheur, and Perineal Outcomes: Informing Women About Choices for Vaginal Birth. Birth, 29: 18-27.

Snow, R., Neubert, A. Peripartum Pubic Symphysis Separation: A Case Series and Review of the Literature. Obstetrical & Gynecological Survey: July 1997 - Volume 52 - Issue 7 - pp 438-443

Soong B, Barnes M. Maternal position at midwife-attended birth and perineal trauma: is there an association? Birth. 2002;32(3):164-169.

Harry Oxorn, MD Human Labor and Birth (University of Ottawa, Ontario, Canada,McGraw-Hill Professional Publishing)1986

Posted by: Amanda K. Blaz, PT, DPT

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