The Dreaded Persistent Occiput Posterior
Laboring women, midwives, nurses and doulas all have reasons to hate the dreaded persistent OP position of the fetal head.
When a baby descends into the pelvis with the face up, a woman will typically start to complain of lower back pain and uncomfortable contractions days or weeks before her due date, and become increasingly frustrated, impatient, and sleep-deprived. Time goes by, the pain continues, and there is no sign that true labor has begun, no cervical change or fetal descent. Then, when labor does finally get going and the woman mentions that her contractions are strongest in her back, optimism for a fast, straightforward labor and birth begins to fade, and, as the day or night wears on with more pain, little progress, and, finally maternal exhaustion and pleas to do something, the reality of the situation becomes unavoidable. On vaginal exam, the baby’s head seems jammed into the front of the pelvis, with plenty of room at the back. There tends to be a lot of caput (swelling of the baby’s scalp) and molding (overlapping of fetal skull bones which can produce a pointed or flattened shape to the baby’s head). It is frequently not possible to get a good assessment of position by feeling for sutures and fontanels. (In one study, only 31% of digital assessments were accurate in the first stage of labor, and only 65% in the second stage. Further, the exam was more likely to be wrong if the position was posterior (Souka et al).) (Illustration from Lusk, 1894).
The incidence of persistent occiput posterior babies at delivery is about 5.5% overall; 7.2% in nulliparas (first-time moms) and 4.0% in multiparas (Ponkey et al). One study using ultrasound to determine the position at the beginning of labor found that only one-third of persistent posteriors begin labor as posteriors and fail to rotate; the other two-thirds develop through a malrotation during labor from an initially occipito-anterior (face down) position (Gardberg et al). Another ultrasound study, however, found that rotation of the fetal head is highly unlikely when labor begins with the head in the anterior position, and that persistent posterior position developed through failure to rotate from an initial posterior or transverse position (Souka et al).
With a persistent posterior, both first and second stages are prolonged (Ponkey et al). However, longer second stages do not in themselves cause worse maternal or neonatal outcomes; in one study, as long as the fetus was stable, the second stage could continue without harm to mother or baby (Kuo et al). The likelihood of cesarean section or instrumental delivery (forceps or vacuum extractor) is greater when there is a persistent posterior position; in fact, the 5.5% of persistent posteriors account for 12% of all cesarean deliveries performed for dystocia or lack of labor progress (Fitzpatrick et al). Persistent posterior positions are associated with an increased incidence of premature rupture of the membranes, oxytocin induction and augmentation, epidural analgesia, chorio-amnionitis (infection of the amniotic fluid), , episiotomies, severe perineal lacerations, vaginal lacerations, excessive blood loss, and postpartum infection (Pearl et al, Ponkey et al). Worse, there is a sevenfold increase in the incidence of anal sphincter injury, that is, third- or fourth-degree perineal lacerations (Fitzpatrick et al). Babies delivered from the posterior position were more likely to have Erb’s Palsy and facial nerve palsy than those delivered from the anterior position (Pearl et al). Obviously, for many reasons, no one is happy when a posterior position is suspected or confirmed.
What factors are associated with the likelihood of a persistent posterior position? Previous cesarean birth, nulliparity, prolonged pregnancy, higher maternal BMI (body mass index), shorter maternal stature, and large babies are factors mentioned in the obstetric literature. However, midwife Jean Sutton and childbirth educator Pauline Scott in their book, Understanding and Teaching Optimal Foetal Positioning, suggest that our modern lifestyle, particularly our propensity to sit and relax on soft, semi-reclining furniture such as sofas and easy chairs as we watch television, and to ride in “bucket” car seats, rather than sitting upright on straight-backed chairs, may contribute to posterior babies. They also note that household labor, for example, scrubbing floors on hands and knees (come on, when is the last time you did that?), and ladylike posture and good deportment used to promote proper alignment of the fetus in the pelvis during the last few months of pregnancy.
Sutton and Scott state that “if a woman (primagravida) regularly uses upright and forward leaning postures, particularly during the last 6 weeks of her pregnancy (the last 2-3 weeks for a multigravida), her baby is given a excellent chance of positioning itself into the OA position. This is because when the pelvis tilts forwards, it allows more space for the broad biparietal diameter of the foetal head to enter the pelvic brim (p. 25).” The authors suggest postures where the woman’s knees are lower than her hips. For sleeping, they advocate an exaggerated side-lying position, with pillows behind her back and the upper leg forward so that the knee touches the mattress; “this ensures that her abdomen is forwards, creating a ‘hammock’ for her baby.” In addition to these postures, Sutton and Scott recommend forward-leaning positions (hands and knees), swimming, yoga, and alternative medicine (acupuncture, acupressure, and homeopathics) to encourage the baby to enter the pelvic in the correct alignment.
During the second stage of labor, Sutton and Scott strongly recommend positions that allow the woman to throw her pelvis forward, lifting the sacrum and coccyx out of the way as the fetal head enters the birth canal. Michel Odent refers to this pelvic thrusting as the “foetal ejection reflex,” an involuntary and intuitive motion that women will perform spontaneously if their position and pushing efforts are not directed and if they are not anesthetized. In a squatting position, a woman must have her feet flat on the ground, have her spine straight, and be supported in order to perform this motion. On hands and knees, with her weight balanced between her hips and her hands clutching something higher than her waist, the woman can easily perform this forward thrust. On a birthing stool, the woman can arch her back and flex her pelvis. Needless to say, a woman flat on her back, sitting in bed, or semi-reclining – not to mention a woman who is numb from the torso down with an epidural – is incapable of achieving the optimal position, and the baby is much more likely to become stuck in the birth canal.
Sutton and Scott advise against the prevalent practice of telling the woman in second stage to round her back, put her chin on her chest, lift her knees and hold them while holding her breath and pushing. This position, they state, is physiologically unsound, increasing the curve of Carus and the need for voluntary bearing down. (Picture the baby attempting to negotiate a curved rather than a straight tube.)
If, as so often happens, a woman is anesthetized with an epidural and cannot move into the optimal positions, there are alternatives to try. Exaggerated side-lying positions as described above can encourage the baby to rotate; try first one side for five or six contractions, then change to the other side. Many midwives believe that it is the changing, rather than the position, that impels the baby to move. Another position that works occasionally when nothing else does is what my colleague Polly Malby calls the “stranded beetle;” flat on the back with legs hyper-flexed and held by support persons. This position is usually my last shot for women with epidurals, and it has worked many times when I was near despair.
In the Gentle Birth Midwifery Archives,, Ronnie Falcao, LM, MS describes a “Pubic Lift Technique” that she learned at an ACNM educational session. “This is a technique used by the speaker-as well as other midwives, to increase the pelvic diameter to facilitate delivery esp. in OP presentations- Presenter said that using technique can help rotate the OP to OA or may just allow delivery in OP position. … The technique (used in 2nd stage) done during a vaginal exam-with mom in dorsal position -during ctx – place examining fingers under pubic bone- pads up, avoiding the urethral meatus, apply firm traction upwards on pubic bone while mom bears down. Technique may be repeated with ctx until successful in turning or bring head down and under pubic bone. The technique is suggested for use when other more generally used techniques such as position changes etc. have been tried but have not been successful.” The Gentle Birth website has other suggestions for dealing with a malpositioned baby; they are listed at http://www.gentlebirth.org/archives/position.html.
I have received many email requests for help from women who underwent cesarean section for a persistent posterior and stalled labor with their first baby; many of them have asked their obstetricians what they can do to prevent this from happening again, and the response is that there is nothing they can do. Sutton and Scott give them hope and effective tools to work with. Both Understanding and Teaching Optimal Foetal Positioning and Pauline Scott’s new book, Sit Up and Take Notice! are available from Amazon. Optimal Foetal Positioning is also available from the MidwiferyToday website. In Canada, it is available at the Parentbooks website. Every pregnant woman who wants her baby to enter labor in the optimal position would do well to obtain a copy of this book, and every midwife, labor nurse, and doula needs a reference copy.
To read an article by a woman who put Sutton and Scott’s techniques into practice for her second birth after a cesarean section with the first, see the “Victorious Birth after Cesarean” website, http://www.victoriousbirth.com/ofp.htm. This article originally appeared in Midwifery Today Magazine.
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Sutton J & Scott P. Understanding and teaching optimal foetal positioning. Tauranga, New Zealand:Birth Concepts, 1995.