This is a collection of references about maternal positioning during labor and birth. It's from the endnotes of Jock Doubleday's book Spontaneous Creation. Bold text is the original body text, and the plain text are his references.
"Except for being hanged by the feet, the supine position is the worst conceivable position for labor and delivery." (Dr. Roberto Caldeyro-Barcia, The Family Practice News, 1975:11) in Laura Kaplan Shanley, Unassisted Childbirth, 15)
Being hanged by the feet may in fact present considerable advantages over lying on one's back. No studies have been performed. But a number of trials do suggest that upright positions give greater advantages in childbirth than do backlying positions. See, for instance, Allahbadia, G.N., and P.R. Vaidya, "Why deliver in the supine position?" Aust NZ J Obstet Gynaecol 32(2) (1992):104-106; Bhardwaj, N., J.A. Kukade, S. Patil, and S. Bhardwaj, "Randomised controlled trial on modified squatting position of delivery," Indian J Maternal and Child Health 6(2) (1995):33-39; Chen, S.Z., K. Aisaka, H. Mori, and T. Kigawa, "Effects of sitting position on uterine activity during labor," Obstet Gynecol 79 (1987):67-73; Liddell, H.S. and P.R. Fisher, "The birthing chair in the second stage of labour," Aus NZ J Obstet Gynaecol 25 (1985):65-68; Gardosi, J., S. Sylvester, and C.B. Lynch, "Alternative positions in the second stage of labour: a randomized controlled trial," Br J Obstet Gynaecol 96 (1989a):1290-1296; Gardosi, J., N. Hutson, and C.B. Lynch, "Randomised, controlled trial of squatting in the second stage of labour," Lancet 2 (1989b):74-77. See also Golay, J., et al., "The squatting position for the second stage of labor: effects on labor and maternal ad fetal well-being," Birth 20(2) (June 1993):73-78.
Pam England and Rob Horowitz write: "When a mother having back labor lies on her back, the pain becomes unbearable as the [back of the] baby's head pushes hard against her sacrum during contractions. Lying flat on her back will not only slow (or stop) cervical dilation, but may also prevent the rotation of the baby's head to a face-down position. This is one cause of "posterior arrest," which doctors may try to correct with pitocin, epidurals, forceps or a Cesarean birth. . . . Avoid the lithotomy position. This unnatural position is advantageous only to the doctor. . . . Stirrups also may cause painful cramping, numbness, or blood clots in the legs. In addition, some women experience this position as degrading, vulnerable and powerless." (Birthing from Within, 143, 145)
Janet Isaacs Ashford writes: "According to the controlled clinical trials surveyed by Enkin, Keirse, and Chalmers, lying down on the back and sitting during labor are associated with reduced blood flow to the uterus, resulting in contractions that are less effective and more frequent. Lying on the side or standing up improves blood flow and the efficiency of contractions. In addition, women who are upright or lying on their sides have shorter labors and use less narcotic analgesia, epidural anesthesia, and oxytocin augmentation than those who are supine (Roberts, 1989). Many hospitals now allow women to walk and assume comfortable positions during labor, though the use of continuous electronic fetal monitoring can restrict the mother's mobility. . . . Enkin, Keirse, and Chalmers also found that use of an upright posture when the mother is pushing shortens the length of second-stage labor. . . . Babies born to women in upright postures have fewer abnormal hear rate patterns and less chance of low Apgar scores (Sleep, Roberts, and Chalmers, 1989). Women prefer the upright posture for birth and report less pain and backache than in the supine posture. . . . The use of a squatting posture for birth has been shown to increase intra-abdominal pressure and also increase the sagittal diameter of the pelvic outlet (Davies and Renning, 1964; Borell and Fernstrom, 1967; Russell, 1982). Both factors can contribute to a shorter, more effective labor. However, researchers note that Western women are not accustomed to assuming a squatting posture (for defecation or resting, for example) and many find it difficult to assume this position for birth. Conventional maternity wards are often equipped with labor beds and delivery tables that encourage or enforce the supine posture." ("Posture for Labor and Birth," The Encyclopedia of Childbearing, Barbara K. Rothman, ed., 314). See also Golay, J., et al., "The squatting position for the second stage of labor: effects on labor and maternal ad fetal well-being," Birth 20(2) (June 1993):73-78.
For information on the squatting position for birth, see Russell, J.G., "The rationale of primitive delivery positions," Br J Obstet Gynaecol 89 (September 1982):712-715; McKay, S., "Squatting: an alternate position for the second stage of labor," The American Journal of Maternal/Child Nursing 9 (May/June 1984):181-183. See also Golay, J., et al., "The squatting position for the second stage of labor: effects on labor and maternal ad fetal well-being," Birth 20(2) (June 1993):73-78. See also Robbie E. Davis-Floyd, Birth as an American Rite of Passage, 86-87.
When you endeavor to give birth on your back, your heavy uterus compresses the major maternal blood vessels (Bienarz, J., et al., "Aortocaval compression by the uterus in late human pregnancy: II. An arteriographic study," Am J Obstet Gynecol, 100 (1968):203; Goodlin, R.C., "Aortocaval compression during cesarean section: a cause of newborn depression," Obstet Gynecol 37 (1971):702; Humphrey, M., et al., "The influence of maternal posture at birth on the fetus," J Obstet Gynaecol Br Commonwealth 80 (9173):1075 in Yvonne Brackbill, et al., Birth Trap, 13)
...interfering with circulation and decreasing blood pressure (Bienarz, J., et al., "Aortocaval compression by the uterus in late human pregnancy: II. An arteriographic study," Am J Obstet Gynecol, 100 (1968):203; Goodlin, R.C., "Aortocaval compression during cesarean section: a cause of newborn depression," Obstet Gynecol 37 (1971):702; Humphrey, M., et al., "The influence of maternal posture at birth on the fetus," J Obstet Gynaecol Br Commonwealth 80 (9173):1075 in Yvonne Brackbill, et al., Birth Trap, 13; see also Flowers, C., Obstetric Analgesia and Anesthesia (New York: Hoeber, Harper & Row, 1967); James, L.S., "The effects of pain relief for labor and delivery on the fetus and newborn," Anesthesiology 21 (1960):405-430; Blankfield, A., "The optimum position for childbirth," Med J Aust 2 (1965):666-668 in Doris Haire, The Cultural Warping of Childbirth, 17)
...increases the possibility of fetal distress (Flynn, A.M. et al., "Ambulation in labour," Br Med J 26 (1978):591; Humphrey, M., et al., "The influence of maternal posture at birth on the fetus," J Obstet Gynaecol Br Commonwealth 80 (1973):1075 in Yvonne Brackbill, et al., Birth Trap, 13. See also Laura Kaplan Shanley, Unassisted Childbirth, 24. See also Lumley, J., "Antepartum fetal heart rate tests and induction of labour," in Young, D., ed., "Obstetrical intervention and technology in the 1980s," Women's Health 7 (1982):9.)
Upright birthing positions are associated with more intense and more efficient contractions (See Marjorie Tew, Safer Childbirth? A Critical History of Maternity Care, 33; Chan, D.P.C., "Positions during labour," Br Med J 1 (1963):100-102; Flynn, A.M. et al., "Ambulation in labour," Br Med J 26 (1978):591; McManus, T.J. and A.A. Calder, "Upright posture and the efficiency of labour," Lancet 1 (1978):72-74; Diaz, A.G., R. Schwarcz, R. Fescina, and R. Caldeyro-Barcia, "Vertical position during the first stage of the course of labor, and neonatal outcome," Eur J Obstet Gynecol Reprod Biol 11 (1980):1-7; Williams, R.M., M.H. Thorn, J.W.W. Studd, "A study of the benefits and acceptability of ambulation in spontaneous labour," Br J Obstet Gynaecol 87 (1980):122-126; Hemminki, E. and S. Saarikoski, "Ambulation and delayed amniotomy in the first stage of labor," Eur J Obstet Gynecol Reprod Biol 15 (1983):129-139; Melzack, R., E. Belanger, and R. Lacroix, "Labor pain, effect of maternal position on front and back pain," J Pain symptom Manegem 6 (1991):476-480 in World Health Organization, Care in Normal Birth, 1999)
Elizabeth Noble writes: "Squatting, while uncomfortable for most people without prior practice, offers one of the most functional positions for birth. According to studies in Sweden by Dr. Christian Ehrstrom, when a mother squats the pelvic outlet is at its widest, increased by one to two centimeters. The pelvis is completely tilted to align with the spine, making the most curved passage for the baby's descent. The contraction of the abdominal muscles is very efficient in squatting as they are in a shortened, middle position of their range. Not only does gravity provide additional force from above, but there is no counterforce from below. The vagina becomes shorter and wider, and less effort is required by the mother to open up and let the baby out at her own pace. During crowning of the baby's head, there is an equal stretch all around the perineum, so that this muscular membranous "cuff" is least likely to tear . . . Women who squat for birth can generally deliver their babies without any manual assistance at all. Gravity and the free space around the perineum allow the baby's rotation maneuvers to be accomplished spontaneously." (Childbirth with Insight, 78). See also Golay, J., et al., "The squatting position for the second stage of labor: effects on labor and maternal ad fetal well-being," Birth 20(2) (June 1993):73-78.
"It was established in 1976 than an increase of 30 to 40 mmHg pressure is exerted by the fetal head on the cervix as a result of the effects of gravity, that is, standing instead of lying down. This means that, although the frequency of the contractions is the same, the effectiveness of the contractions is much greater, and hence the efficiency and rate of the dilatation of the cervix is improved. . . . In order to prove the superiority of the upright position in practice, the 1976 study alternated the posture of women volunteers every half-hour from the dorsal to the standing position. There was an abrupt fall in the intensity of the contractions when the women lay down, and the effectiveness of contractions in dilating the cervix was doubled when they stood up. The mothers also found the standing half-hour much less uncomfortable or painful; it was often difficult to persuade them to lie down again."
Sally Inch, Birthrights, 31; see Schwarcz, R., A.G. Diaz, R. Fescina, and R. Caldeyro-Barcia, Latin American Collaborative Study on Maternal Posture in Labor (1977); reported in Birth and the Family Journal 6(1)1979.