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Posts tagged “posterior

Does baby’s position matter in labour and can we do anything about it?

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Reply to Catie Mehl of Columbus Birth & Parenting and Angela Horn from Tuscon doulas recently published blog posts about malposition.

http://tucsondoulas.com/does-babys-position-matter-pt2/

Prevalence of OP prior to labour

Up to approx. 30% of babies are OP before labour begins.[1]

Some studies have found that fetal position before labour does not affect birth outcome[2] but others have found the opposite, in one study occipital position was found to be a factor in predicting successful induction[3] with cervical length being longer in OP positions prior to induction.

Around 80% of babies that are OP before labour begins, will rotate in labour[1]

But the longer a baby stays OP in labour, the more likely they are to stay that way.[4]

The deflexion associated with OP may be more important than the fetal position.[3]

Malposition effects labour progress

Persistent OP is associated with prolonged first and second stages of labor and augmentation [5-7]

Malpositioned labours significantly more often cross the partogram action line[8]

Malposition effects maternal and fetal outcomes

Women whose babies that are malpositioned during labour and birth are more likely to have obstetric interventions, including assisted delivery and operative birth [6 9 10]

The incidence of persistent occiput posterior position was associated with significantly higher incidences of induction of labor, oxytocin augmentation of labor, epidural use, and prolonged labor[5]

Maternal movement in labour improves birth outcomes

Can maternal position changes in labour effect rotation from OP to OA?

Most intervention studies using maternal position to try to rotate babies from OP to OA have been unsuccessful[9 11]  although studies have tended to be for short durations (-10 minutes), and include participants that have an epidural (approx. 90%)

One study has been successful in effecting rotation from OP to OA using maternal movement. The authors conducted an observational cohort study of women in Padua, Italy having their first baby. They grouped women into Group-A when they spent more than 50% of their labour in recumbent position (supine or lateral) and in Group-B when they preferred an alternative position (upright, squatting, sitting on the ball, or “on all fours” position) the OP rate at the start of labour was comparable in two groups with 40.6% in Group-A and 36.5% in Group-B.

A strong significant difference was found in terms of delivery outcome.

CS was necessary in 27 patients: 46.4% in Group-A compared to the 12.3% in Group-B.

Significant differences in terms of OP persistence at delivery were also found in those delivering vaginally: in Group-A patients, OP persisted till birth in 39.6% of the cases while in Group-B only in 28% of the cases[12]

Other evidence for benefits of maternal movement in the first stage

Upright positions increase contraction strength. Women labouring in upright, non-recumbent positions have fewer POP deliveries, shorter labours and lower rates of assisted deliveries and CS[12]

Sims’ posture on the same side as the fetal spine has been recommended to enhance rotation from posterior to anterior[13]

Prince of Songkla University Cat (leaning over back of bed at 60 degree angle on knees)and upright positions together with music reduced the duration of active phase of labour and labour pain in primiparous women compared to oxytocin[14]

Cochrane review: Maternal positions and mobility during first stage labour-“Walking and upright positions in the first stage of labour reduces the duration of labour, the risk of caesarean birth, the need for epidural, and does not seem to be associated with increased intervention or negative effects on mothers’ and babies’ wellbeing.”[15]

Other evidence for benefits of maternal movement in the Second stage

Any upright or lateral birth positions compared with supine or lithotomy positions have been associated with reduced duration of second stage of labour, reduction in operative delivery, reduction in episiotomies, reduced reporting of severe pain in the second stage, fewer abnormal fetal heart patterns[16]

“Use of the supine position is associated with negative maternal, fetal, and neonatal hemodynamic outcomes. Despite the persistence of the use of recumbent positions for birth, the evidence supports the merit of upright positions. “

Kneeling squat position significantly increases the bony transverse and anteroposterior dimension in the mid pelvic plane and the pelvic outlet[17]

In a study using MR obstetric pelvimetry an upright birthing position significantly expands female pelvic bony dimensions, suggesting facilitation of labor and delivery[18]

Epidural use

Women with epidurals that change position[19] (every half hour from hands and knees, sitting etc in the passive part of second stage (giving time for the head to come down) and push in a lateral position with the upper hip abducted had greatly reduced assisted delivery rates (19.8% vs 42.1%) higher rates of intact perineum ( (40.3% vs 12.2%), lower episiotomy rate (s (21.0% in vs 51.4%) and time actively pushing, without incurring any other adverse maternal or fetal outcomes[20]. Peanut balls have also been found to improve outcomes for women with an epidural. [21]

Squatting

The use of the squatting position in managing the second stage of labor results in less instrumental delivery, extension of episiotomy and perineal tearing compared with the supine position[22 23]

Women prefer freedom to move in labour

Freedom to change positions in labour has been identified as integral to a feeling of control and the management of pain in labour, due to the physical and psychological benefits[24]

Women have described being in more control over their pushing in the second stage when they were in an upright position compared to a supine position[25]

 

Is operative birth necessary?

CPD

In a review of >225 thousand birth records in the United states (2002-08) half of Caesarean Deliveries for dystocia in induced labor were performed before 6 cm of cervical dilation. Among intrapartum CDs, approximately half were performed for ‘failure to progress’ or ‘cephalopelvic disproportion’.[26]

It has been reported that most cases of reported cephalopelvic disproportion (CPD) result from malposition of the fetal head within the pelvis (asynclitism) or from ineffective uterine contractions. True disproportion is an unlikely diagnosis because two thirds or more of women undergoing cesarean delivery for this reason subsequently deliver even larger newborns vaginally[27]

https://www.youtube.com/watch?v=roFVkDV45MM

Could we reduce intervention for dystocia and malposition with more time?

A review of the evidence relating to dystocia found that current understandings rest on outdated definitions of active first stage of labour, its progress and on treatments without a strong evidence base. These include the cervical dilatation threshold for active first stage, uncertainty over whether a reduced rate of dilatation and reduced strength of uterine contractions always represent pathology and the effectiveness of amniotomy/oxytocin for treating dystocia[28]

It has been suggested that one of the ways to safely prevent primary caesarean deliveries is to increase the active phase of labour start to 6cm and the safe duration of the second stage to at least 2 hours for women having a second or subsequent baby and 3 hours for women having their first baby.[29] or longer with an epidural although the safety of this is contested by some. [30]

International findings

Obstructed labour mostly caused by malposition (and often labelled as CPD) is common in lower income countries and has a high rate or maternal and fetal mortality and morbidity. More needs to be done to prevent and resolve malposition in situations where safe obstetric intervention may not be feasible to save mothers and babies lives and futures[31]

Women in Low and middle income countries (LMIC) are described as having three delay to obstetric care. (1) deciding to seek appropriate medical help for an obstetric emergency; (2) reaching an appropriate obstetric facility; and (3) receiving adequate care when a facility is reached[32]

http://blogs.msf.org/en/staff/blogs/may-the-forceps-be-with-you/one-foot-in

Maternal and fetal morbidity and mortality is often due to this delayed treatment.

Prolonged obstructed labor can result in fistulas. Because obstetric fistulas are caused by tissue compression, the time interval from obstruction to delivery is critical. Women may not deliver in health care facilities if they do not meet their needs. (this includes the need to move around in labour and use upright positions to birth in, which may be discouraged in the hospital setting) There may be transport and cost implications or Beliefs that problems in labor arise from disturbances in the social environment (and may be caused by actions of the mother) rather than as simple problems of obstetrical mechanics [33]

Even after arrival at a health facility mean waiting time for women admitted with complications was as much as 24 h before treatment.[34]

http://blogs.msf.org/en/staff/blogs/may-the-forceps-be-with-you/before-the-beginning

Barriers and facilitators maternal movement in labour

Barriers to maternal movement in labour include: (1) lack of space, (2) inadequate support, (3) use of unwarranted debilitating technology, and (4) movement restricting pain relief[35]

Difficulty in conducting research relating to maternal movement in labour, which is often dynamic and needs to be directed by the woman, means that amassing strong evidence of the efficacy of maternal movement to resolve malposition is complicated. Cultural influences and provider influences also effect choice of maternal position. [36 37]

Use of a pool in labour has been suggested to increase maternal ability to change position[38] and also mobile telemetry for high risk women to allow greater mobilisation and use of the pool.[39]

Fathers with a partner having an upright birth position were more likely to have had a positive birth experience, to have felt comfortable and powerful compared to spontaneous vaginal births where women adopting a horizontal birth position[40]

SUMMARY

Malposition’s are the root cause for much of the morbidity and mortality and unexpected intervention in labours worldwide. There is a body of evidence that maternal mobility in labour improves outcomes and may aid rotation. More research is needed that can adequately measure maternal mobility in labour and interventions that match the multifaceted practices that midwives and doulas use to support women with prolonged labour or suspected malposition.

Women may want to mobilise in labour but feel restricted by social/cultural expectations (for example the use of the bed in the maternity room[41]) or restricted by the technology being used (CFM, drip).

Doulas and midwives can help to facilitate women’s choices by:

  • Antenatal education that provide women and their partners practical experience of maternal positions that can facilitate labour and birth
  • Discussing the barriers and enablers of maternal movement
  • Practical support in labour if technology is needed (suggesting mobile telemetry as a possibility if available, holding monitors in place while women use birth balls or change position with CFM)
  • Suggesting movement changes in labour that might aid women’s comfort or rotation
  • Suggesting the use of a peanut ball if women have an epidural or need to rest in a recumbent position
  • Suggesting position changes in the second stage (particularly if there is a delay or little change in descent)
  • Rebozo can be a useful tool when women have difficulty moving (due to exhaustion, pain, pain relief or technology that restricts movement)42]

 

  1. Verhoeven CJ, Mulders LG, Oei SG, et al. Does ultrasonographic foetal head position prior to induction of labour predict the outcome of delivery? European Journal of Obstetrics & Gynecology and Reproductive Biology 2012;164(2):133-37
  2. Ahmad A, Webb S, Early B, et al. Association between fetal position at onset of labor and mode of delivery: a prospective cohort study. Ultrasound in Obstetrics & Gynecology 2014;43(2):176-82
  3. Ashour ASA, ABDELLA RM, GHAREEB HO, et al. Preinduction ultrasonographic measurements as a predictor of successful induction of labor in prolonged pregnancy in primigravidas. 2013
  4. Vitner D, Paltieli Y, Haberman S, et al. Prospective multicenter study of ultrasound‐based measurements of fetal head station and position throughout labor. Ultrasound in Obstetrics & Gynecology 2015;46(5):611-15
  5. Fitzpatrick M, McQuillan K, O’Herlihy C. Influence of persistent occiput posterior position on delivery outcome. Obstetrics & Gynecology 2001;98(6):1027-31
  6. Ponkey SE, Cohen AP, Heffner LJ, et al. Persistent fetal occiput posterior position: obstetric outcomes. Obstetrics & Gynecology 2003;101(5, Part 1):915-20
  7. Senécal J, Xiong X, Fraser WD, et al. Effect of fetal position on second-stage duration and labor outcome. Obstetrics & gynecology 2005;105(4):763-72
  8. Mathisen M, Olsen RV, Andreasen S, et al. Is it possible to detect malposition of the vertex at an early stage in labour? A case-control study. Sexual & Reproductive Healthcare 2014;5(4):185-87
  9. Desbriere R, Blanc J, Le Dû R, et al. Is maternal posturing during labor efficient in preventing persistent occiput posterior position? A randomized controlled trial. American journal of obstetrics and gynecology 2013;208(1):60. e1-60. e8
  10. Gardberg M, Leonova Y, Laakkonen E. Malpresentations–impact on mode of delivery. Acta obstetricia et gynecologica Scandinavica 2011;90(5):540-42
  11. Guittier M, Othenin‐Girard V, Gasquet B, et al. Maternal positioning to correct occiput posterior fetal position during the first stage of labour: a randomised controlled trial. BJOG: An International Journal of Obstetrics & Gynaecology 2016
  12. Gizzo S, Di Gangi S, Noventa M, et al. Women’s choice of positions during labour: return to the past or a modern way to give birth? A cohort study in Italy. BioMed research international 2014;2014
  13. Ridley RT. Diagnosis and intervention for occiput posterior malposition. Journal of Obstetric, Gynecologic, & Neonatal Nursing 2007;36(2):135-43
  14. Phumdoung S, Youngwanichsetha S, Mahattanan S, et al. Prince of Songkla University Cat and upright positions together with music reduces the duration of active phase of labour and labour pain in primiparous women compared to oxytocin. Focus on Alternative and Complementary Therapies 2014;19(2):70-77
  15. Lawrence A, Lewis L, Hofmeyr GJ, et al. Maternal positions and mobility during first stage labour. Cochrane Database Syst Rev 2013;8:Cd003934
  16. Gupta JK, Hofmeyr GJ, Shehmar M. Position in the second stage of labour for women without epidural anaesthesia. The Cochrane Library 2012
  17. Reitter A, Daviss B-A, Bisits A, et al. Does pregnancy and/or shifting positions create more room in a woman’s pelvis? American journal of obstetrics and gynecology 2014;211(6):662. e1-62. e9
  18. Michel SC, Rake A, Treiber K, et al. MR obstetric pelvimetry: effect of birthing position on pelvic bony dimensions. American Journal of Roentgenology 2002;179(4):1063-67
  19. Lape LA. The relationship between the incidence of occiput posterior fetal position at birth to maternal labor positions in patients with epidurals: Northern Kentucky University, 2011.
  20. Walker C, Rodríguez T, Herranz A, et al. Alternative model of birth to reduce the risk of assisted vaginal delivery and perineal trauma. International urogynecology journal 2012;23(9):1249-56
  21. Tussey CM, Botsios E, Gerkin RD, et al. Reducing length of labor and cesarean surgery rate using a peanut ball for women laboring with an epidural. The Journal of Perinatal Education 2015;24(1):16-24
  22. Ahmed MA-GS, Youssef M. Comparison between squatting versus supine (lithotomy) positions during the passive second stage of labor without epidural anesthesia in nulliparous women: a prospective cohort study. Journal of Evidence-Based Women’s Health Journal Society 2015;5(3):140-42
  23. Dani A, Badhwar V, Sawant G, et al. COMPARATIVE STUDY OF SQUATTING POSITION VS DORSAL RECUMBENT POSITION DURING SECOND STAGE OF LABOUR.
  24. Johansson M, Thies-Lagergren L. Swedish fathers’ experiences of childbirth in relation to maternal birth position: a mixed method study. Women and Birth 2015;28(4):e140-e47
  25. De Jonge A, Lagro-Janssen A. Birthing positions. A qualitative study into the views of women about various birthing positions. Journal of Psychosomatic Obstetrics & Gynecology 2004;25(1):47-55
  26. Epidemiology of cesarean delivery: the scope of the problem. Seminars in perinatology; 2012. Elsevier.
  27. Horsager R, Roberts S, Rogers V, et al. Williams Obstetrics, Study Guide: McGraw Hill Professional, 2014.
  28. Karaçam Z, Walsh D, Bugg GJ. Evolving understanding and treatment of labour dystocia. European Journal of Obstetrics & Gynecology and Reproductive Biology 2014;182:123-27
  29. Caughey AB, Cahill AG, Guise J-M, et al. Safe prevention of the primary cesarean delivery. American journal of obstetrics and gynecology 2014;210(3):179-93
  30. Leveno KJ, Nelson DB, McIntire DD. Second-stage labor: how long is too long? American journal of obstetrics and gynecology 2015
  31. Higashi H, Barendregt J, Kassebaum N, et al. Surgically avertable burden of obstetric conditions in low‐and middle‐income regions: a modelled analysis. BJOG: An International Journal of Obstetrics & Gynaecology 2015;122(2):228-36
  32. Barnes-Josiah D, Myntti C, Augustin A. The “three delays” as a framework for examining maternal mortality in Haiti. Social science & medicine 1998;46(8):981-93
  33. Wall LL. Overcoming phase 1 delays: the critical component of obstetric fistula prevention programs in resource-poor countries. BMC pregnancy and childbirth 2012;12(1):68
  34. Cavallaro FL, Marchant TJ. Responsiveness of emergency obstetric care systems in low‐and middle‐income countries: a critical review of the “third delay”. Acta obstetricia et gynecologica Scandinavica 2013;92(5):496-507
  35. Hollins Martin CJ, Martin CR. A narrative review of maternal physical activity during labour and its effects upon length of first stage. Complementary therapies in clinical practice 2013;19(1):44-49
  36. Martin CJH, Kenney L, Pratt T, et al. The Development and Validation of An Activity Monitoring System for Use in Measurement of Posture of Childbearing Women During First Stage of Labor. Journal of Midwifery & Women’s Health 2015;60(2):182-86
  37. Nieuwenhuijze MJ, Low LK, Korstjens I, et al. The Role of Maternity Care Providers in Promoting Shared Decision Making Regarding Birthing Positions During the Second Stage of Labor. Journal of Midwifery & Women’s Health 2014;59(3):277-85
  38. Hall E. The use of water immersion in the facilitation of ‘normal labour’. Diffusion-The UCLan Journal of Undergraduate Research 2014;7(1)
  39. Jackson R. The use of water during the first stage of labour: Is this a safe choice for women undergoing VBAC? British Journal of Midwifery 2013;21(6)
  40. Hasman K, Kjaergaard H, Esbensen BA. Fathers’ experience of childbirth when non-progressive labour occurs and augmentation is established. A qualitative study. Sexual & Reproductive Healthcare 2014;5(2):69-73
  41. Townsend B, Fenwick J, Thomson V, et al. The birth bed: A qualitative study on the views of midwives regarding the use of the bed in the birth space. Women and Birth 2015
  42. Cohen SR, Thomas CR. Rebozo technique for fetal malposition in labor. Journal of Midwifery & Women’s Health 2015;60(4):445-51

 

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Are the numbers of women having posterior babies increasing? Historical references to the Occiput Posterior position

It has been suggested that malposition (and occiput posterior presentation) has been increasing in incidence and also that one cause of this may be our sedentary lifestyle.
In Jean Sutton and childbirth educator Pauline Scot’s book, ‘Understanding and Teaching Optimal Foetal Positioning’ they theorise that our tendency to sit back and relax on soft, semi-reclining furniture like sofas and armchairs as we watch television, and spend more time driving ( in “bucket” car seats), rather than walking, may contribute to the incidence of posterior babies. It is also suggested that historically ‘women’s work’ in the home like, scrubbing floors on hands and knees and also a ladylike posture and good deportment promoted proper alignment of the fetus in the pelvis during the last few months of pregnancy.
http://midwifeinsight.com/articles/the-dreaded-persistent-occiput-posterior/
Gail Tully at ‘Spinning babies’ agrees that the modern lifestyle is to blame; and also that research studies prior to ten years ago saw a lower incidence of posterior position.
“There is a rising incidence of posterior babies at the time of birth. The high numbers of posterior babies at the end of pregnancy and the early phase of labor is a change from what was seen in studies over ten years old. Perhaps this is from our cultural habits of sitting at desks, sitting in bucket seats (cars), and leaning back on the couch (slouching).”
http://spinningbabies.com/baby-positions/posterior

The current estimates of posterior presentation range from 12-40% prior to labour, 15-50% in the first stage of labour, 19-25% at 10cm dilation and approximately 20% of babies that are OP at 10cm are still OP at delivery (with a range of 3.8 to 12.2% (mean = 7.6%) (Blasi et al 2010, Malvasi et al 2013, Verhoeven et al 2012)

Historical prevalence of OP position

I was interested to see what historical references to posterior position, prevalence and management could be found in the literature. The earliest reference e to OP position I could find was by WILLIAM D. PORTER, M.D. who published a paper in 1929 in the American medical association journal titled ‘POPULAR FALLACIES CONCERNING OCCIPITOPOSTERIOR POSITIONS OF VERTEX’ this described the wok of Smellie in a book of Midwifery from 1744. He was called by a midwife to a case of dystocia, which he decided was caused by posterior presentation and applied forceps (the outcome here is not known)

A study in 1929 found the incidence of OP to be 29.8 (assuming this was detected by vaginal exam or palpation this may not be entirely accurate) but suggests that the prevalence at that time was similar to now and not significantly lower. (Dodek 1931, Torpin 1945). I would assume most women in that era would not have had the labour saving devices that we have now, so that suggests that posterior position may not be caused by a sedentary lifestyle (probably reassuring to women whose babies posterior and may feel it is there fault for not doing enough activity) that’s not to say that I feel there is no point in antenatal exercise as we know that physical exercise in pregnancy reduces the CS rate (see recent review by Domenjov et al 2014)

Historical OP outcomes

Dodek also states that “It often has been said that the vertex occipitoposterior position is the obstetric complication taking the greatest toll of fetal and maternal life and predisposing toward the greatest morbidity and permanent damage among surviving mothers” and TS Wells in 1891 reported that ‘statistics show that the mortality among infants in occiput posterior
cases is 1 in 5’ (TS Wells – British medical journal, 1891 – ncbi.nlm.nih.gov)

http://jama.jamanetwork.com/article.aspx?articleid=256047

Historical OP management

Babies were often delivered by forceps and this contributed to the high fetal mortality. Hoever it appears that obstetricians from the 18th and 19th century know almost as much as we do now about posterior position, its consequences and resulting negative outcomes (although thankfully we no longer expect posterior position to result in fetal mortality)

Gilbert Strachan in 1939 described the signs of a posterior labour as ‘Slow progress with good pains and a roomy pelvis or ‘Primary inertia with early rupture of the membranes’. He also stated that:

“The prognosis of these cases depend almost entirely on the judgement and patience with which they are treated and the greatest virtue is patience.
In cases that rotate the prognosis for mother and child should be but little influenced, it is in those that persist posterior that damage will be done to both parties, with foetal mortality in this series of 26.6% “

The Walchers position (to avoid the use of forceps or facilitate an easier forces birth) was taught from 1838 in England and doctors found that If the legs hung down freely from the conjugate, increases diameter by 1cm (Fothergill 1898)

• What can we learn from this exploration of the historical references of occiput posterior position?

• The incidence of women having babies in a posterior position appears to be similar in the 18th and 19th century

• Obstetricians were aware that it was persistent OP caused a large proportion of maternal and neonatal morbidity and mortality

• Babies that were unable to be birthed were often delivered by forceps, which had a high mortality and injury risk

• Historically obstetricians were aware that the most important management technique in an OP labour was patience (it may be that we see more persistent OP babies because of a lack of patience, and that women may also be less fit going into labour and spend more of labour lying down than would have been common historically)

Into the future

Obstetricians have been aware of the importance of posterior position to the outcomes of mothers and babies for over 200 years, yet very little progress has been made in reducing the incidence or changing management to improve outcomes, considering the large numbers of women that are effected by malposition, very little research is being conducted to look at effective pre labour or in labour interventions to improve rotation

References

Verhoeven, C. J. M., Rückert, M. E. P. F., Opmeer, B. C., Pajkrt, E., &Mol, B. W. J. (2012). Ultrasonographic fetal head position to predict mode of delivery: a systematic review and bivariate meta‐analysis. Ultrasound in Obstetrics &Gynecology, 40(1), 9-13.

Blasi, I., D’Amico, R., Fenu, V., Volpe, A., Fuchs, I., Henrich, W., &Mazza, V. (2010). Sonographic assessment of fetal spine and head position during the first and second stages of labor for the diagnosis of persistent occiput posterior position: a pilot study. Ultrasound in Obstetrics &Gynecology, 35(2), 210-215.

Malvasi, A., Tinelli, A., Barbera, A., Eggebø, T. M., Mynbaev, O. A., Bochicchio, M., …& Di Renzo, G. C. (2013). Occiput posterior position diagnosis: vaginal examination or intrapartum sonography? A clinical review. The Journal of Maternal-Fetal & Neonatal Medicine, 27(5), 520-526.

PORTER WD. POPULAR FALLACIES CONCERNING OCCIPITOPOSTERIOR POSITIONS OF VERTEX. JAMA. 1929;92(3):221-226. doi:10.1001/jama.1929.02700290031008.
http://jama.jamanetwork.com/article.aspx?articleid=263273

DODEK SM. THE VERTEX OCCIPITOPOSTERIOR POSITION: THE TREATMENT OF MORE THAN FIVE HUNDRED CONSECUTIVE CASES. JAMA. 1931;96(20):1660-1664. doi:10.1001/jama.1931.02720460006002.

Iris Domenjoz, Bengt Kayser, Michel Boulvain, Effect of physical activity during pregnancy on mode of delivery, American Journal of Obstetrics and Gynecology, Volume 211, Issue 4, October 2014, Pages 401.e1-401.e11, ISSN 0002-9378, http://dx.doi.org/10.1016/j.ajog.2014.03.030.
(http://www.sciencedirect.com/science/article/pii/S0002937814002403)

Wells, T. Spencer. “Practical Cure or Disastrous Failure?.” British medical journal 1.1570 (1891): 257.

TORPIN R. THE INFLUENCE OF PLACENTAL SITE ON FETAL PRESENTATION. JAMA. 1945;127(8):442-445. doi:10.1001/jama.1945.02860080014004.

Strachan GI. The Occipito-Posterior Case. Postgraduate Medical Journal 1939;15(165):263-268.

Fothergill WE. WALCHER’S POSITION IN OBSTETRICS. British Medical Journal 1898;1(1931):53.