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 Historical references to the Occiput Posterior position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.
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).”
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I was interested to see what historical references to posterior position, prevalence and management could be found in the literature.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)
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
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.
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.
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.