Childbirth can be classified as one of the true universal human events; every person on earth was gestated and delivered in some manner. Vaginal childbirth is divided into three stages: stage one is the dilation of the cervix and beginning of uterine contractions, stage two is the pushing and delivery of the baby, and stage three is the delivery of the placenta (Hutchison et al., 2019). This review will examine the relationship between the position used during labor stage two and several maternal outcomes. During childbirth there are several common injuries that mothers sustain, including perineal tearing, anal sphincter rupture, pelvic floor damage, and hemorrhaging. Additionally, maternal health complications can stem from medical procedures commonly performed during vaginal delivery: episiotomy and instrumental delivery. An episiotomy is a procedure to cut the perineum and can be used to advance delivery if the fetus is in distress, or it can be performed preemptively to mitigate more severe tearing. Perineal damage, including episiotomy, complicates the post-birth healing process and can cause long-term maternal health issues like bleeding and infection (Warmink-Perdijk et al., 2016). If the birth becomes complicated, medical personnel can use a delivery vacuum or forceps to assist the delivery; however, these interventions increase the risk of infection and injury for mother and child (Quivey, 2009).
Perineal tears are classified into 4 groups: first degree perineal tearing is tearing of the skin of the perineum, second degree tearing involves tearing of the perineum muscle, third degree tearing is tearing of the perineum muscle and anal sphincter, and fourth degree tearing is tearing that extends into the anus and rectum (“Vaginal tears in childbirth”, n.d.). More severe tears cause more damage, take longer to heal, are more painful, and have greater risk for maternal health complications. An episiotomy can be performed to prevent third- and fourth-degree tearing, but it is not necessary for every birth, and routine episiotomy is associated with worse health outcomes than natural first- and second-degree tearing in many cases (Hartmann et al., 2005). Operative vaginal delivery occurs when the fetus needs assistance exiting the birth canal, but a caesarean section is not yet necessary; medical personnel aid the delivery by extracting the baby from the birth canal using forceps or a delivery vacuum. While instrumental assistance is a valuable intervention when necessary, it carries the risk of additional injury to the mother (Liabsuetrakal et al., 2020) and baby (Quivey, 2009).
The dominant birthing position for hospital deliveries in the United States is the supine position, in which the mother is on her back, typically in a hospital bed (Satone, P. D., & Tayade, S. A., 2023). The popularity of the supine position can be attributed to many factors. The position was initially popularized in eighteenth-century France by obstetrician Francois Mauriceau and was known as “the French birthing position” (Dunn, 1991), the position was preferred not by the women giving birth, but by their doctors, who were given easy access to the cervix, vagina, and perineum (De Jonge & Lagro-Janssen, 2004). With the advent of fetal heart rate monitors, the position became preferred because it allowed for continuous monitoring of the fetus, which would not be possible if the laboring patient was upright and mobile (Desseauve et al., 2016). Telemetric fetal heart rate monitors are commercially available, but few hospitals have them since their wired counterparts are still functional. Historically, women have not chosen to deliver in a supine position due to the restriction of sacral (tailbone) movement, instead choosing more upright positions like standing, squatting, and kneeling, or with a birthing aid like a birthing stool or bar (Desseauve et al., 2016).
In this review, three types of birthing position will be discussed: supine, upright, and lateral. Supine positions have the mother on her back with her weight on her back and pelvis and include dorsal and lithotomy positions (Satone, P. D., & Tayade, S. A., 2023). Upright positions have the mother on her feet or knees and include standing, squatting, kneeling, and sitting; these positions can be unaided or aided (Satone, P. D., & Tayade, S. A., 2023). Lateral positions have the mother off her feet and sacrum, typically lying on her side (Satone, P. D., & Tayade, S. A., 2023). Non-supine positions will also be referred to as flexible sacrum positions and alternative positions. This review seeks to determine the impact of birthing position on the duration of the second stage of labor, frequency and severity of perineal injury, and rate of intervention. Births involving a cesarean section or epidural will not be discussed due to the lack of option for birthing position in these instances.
The duration of labor stage two is the amount of time spent actively pushing the baby and has been found to vary between birthing positions. A study of births in Amhara State, Ethiopia, found the average duration of labor stage two in a supine position was 82 minutes, while the average duration of labor in a flexible sacrum position (kneeling, standing, squatting, all fours, and on a birthing seat) was 56 minutes (Badi et al, 2022). A Turkish study found the average duration of stage two in a supine position to be 55 minutes, and 21 minutes in a squatting position (Moralglu et al., 2016). The difference in duration of stage two between supine and alternative positions is attributed to the flexibility of the sacrum by Badi et al. (2022), who propose that the supine position restricts motion of the sacrum and reduces the pushing power of the uterus. In an upright position the force of gravity aligns with the pelvic floor, as opposed to a supine position in which the gravitational force and pelvic floor are perpendicular; however, Ashton-Miller et al. (2009) calculated that the pelvic floor experiences 37 Newtons (N) in an upright position and 19 N in a supine position, 54 N during a uterine contraction, and 120 N during active pushing. These values suggest that while the force of gravity is not negligible, pushing has a much greater effect on the movement of the fetus. In a qualitative study on women’s opinions about their birthing experience, De Jonge and Lagro-Janssen (2004) report that eight out of the ten participating women preferred an upright position because it allowed them greater ability to bear down. The restriction of sacral movement in a supine position leads to longer pushing times, leaving maternal patients in pain for a greater duration.
Injuries to the perineum are some of the most common maternal injuries sustained during childbirth, and can be extremely painful, in some cases causing nerve damage (pudendal nerve entrapment) (Kaur et al., 2023), infections, urinary or anal incontinence, and pain during intercourse (dyspareunia) (Ramar & Grimes, 2023). The rate of perineal injury in a supine position was found to be greater in a study by Zhang et al. (2016), with an intact perineum rate of 33.2% for women who delivered on all-fours and 14.8% for women who delivered in a supine position. Additionally, the researchers found a higher rate of first-degree tearing in women who delivered on all-fours (56.3%) vs women who delivered in a supine position (41.8%). While the increased rate of first-degree tears in an alternative position may be alarming, the higher rate of intact perineum for women on all-fours suggests that skin tears were the most common type sustained, as opposed to deeper tears into the muscle. Third- and fourth-degree tears are much rarer during delivery, and Zang et al. (2020) found that upright birthing positions substantially decreased the chance of tears affecting the anus and anal sphincter. Better perineal outcomes lead to a faster postpartum recovery, and the decreased chance of severe perineum damage in an alternative birthing position suggests better maternal health outcomes than for those who deliver in a supine position.
Episiotomies are also more common in the supine position, one study found the episiotomy rate in the lithotomy position (a variation of supine position with the woman’s legs bent upward in stirrups) to be 34%, while alternative birthing positions had an episiotomy rate of 9% (De Jonge et al., 2004). Meyvis et al. (2012) found an episiotomy rate of 6.7% for those in the lateral position, and 38.2% for those in a supine position. Zhang et al. (2016) reported an episiotomy rate of 1.8% for women on all-fours and 37.7% for women in the supine position. It could be argued that the episiotomy rate in a supine position is greater because an episiotomy is performed while a woman is lying down; however, Warmink-Perijk et al. (2016) found that women who spent labor stage two in a supine position exclusively had episiotomies at a greater rate than those who began in an upright transition then switched to a supine position. The study determined that the greater rate of episiotomies for those who delivered in a supine position could not be attributed to the change in position for the procedure. Instances of assisted birth with vacuum or forceps were also found to be lower in women who delivered in an alternative birthing position (De Jonge et al., 2004). Medical interventions are less frequently needed during delivery in an alternative birthing position than in a supine position.
Analysis of supine and alternative birthing positions found that alternative positions have lower incidence rates for perineal damage, decreased rates of episiotomy and instrument assisted births, and, on average, have a shorter duration of pushing. Studies on birthing positions are limited by many factors: greater popularity of supine positions over alternatives, changes in position over the course of labor stage two, and the large number of birthing positions available. Additionally, childbirth is a medical event and cannot be replicated in a laboratory setting. Restriction of birthing position in hospital births has often been attributed to the need for continuous fetal monitoring, but telemetric fetal heart rate monitors are commercially available and can be used in any birthing position. Overall, the prevalence of the supine position seems to come from the familiarity and convenience for medical staff, not because it has better maternal health outcomes.
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