Age, obesity and uterine contractility…

small_127813925During the last week, two important papers from the Birthplace team have been published. The impact of maternal obesity on intrapartum outcomes in otherwise low risk women: secondary analysis of the Birthplace national prospective cohort study, which has been available online for a few months (and discussed here), was published in print form in the BJOG (Hollowell et al 2013).  Then, just a few days later, The effect of maternal age and planned place of birth on intrapartum outcomes in healthy women with straightforward pregnancies: secondary analysis of the Birthplace national prospective cohort study (Yangmei et al 2014) was published in BMJ Open.

These papers are important for lots of reasons. I was particularly interested to read the latest paper because I have recently been thinking a lot about the issue of alleged poor uterine contractility in women who are larger and/or older than average.  I have also been discussing this with a number of other midwives, and I am particularly not as convinced as some of my esteemed colleagues that overweight women are intrinsically at risk from poor uterine contractility.

It’s just not what I (and apparently a good few of my colleagues) have seen in practice, sorry.

And yes, I know that what I’ve seen in practice is only my experience, but several aspects of national guidance relating to this area are based on the expert opinion of certain other practitioners, so I feel justified in throwing mine into the mix 😉

This is a complex issue and many possibilities exist, which are not necessarily mutually exclusive. Some possibilities to think about here include:

  • Some women have longer labours than others, and this is merely reflective of a normal range.  How boring it would be if every woman had the same labour!  If there are differences, is this actually a problem, or do we just need to adapt our thinking?
  • If there are differences, is it possible that these might be caused not by overweight and age per se, but by the differences in the environments in which we work, which (among many other elements) will include our perception of whether or not certain physical characteristics (such as age and size) are risk factors?
  • Could the kind of care – which might include, for instance, the degree of emphasis that the attendant places on the importance of creating a space that is more likely to enable women to release oxytocin – make a difference?
  • The mere act of labelling someone as ‘at risk’, let alone the increased monitoring which is offered to women who are perceived to be at increased risk, might – understandably – cause those women to feel anxious.  This might, in turn, make it harder for them to relax and release the oxytocin which promotes uterine contractility…

It might well be that, for some reason that we have yet to uncover, women who weigh more or are older have poorer uterine contractility.  But this might be iatrogenic and/or environmentally dependent.  It might be caused, in part, with the growing focus on so-called clinical complexity, and the effect that this has on practitioners’ expectations.  As far as I can see, the theory of reduced uterine contractility is just one theory supported (at the time of writing) by a small number of studies carried out in medicalised environments.  Other environments and other theories exist, and we need more data, and more discussion.

Imagine my delight, then, when the authors of the latest paper have acknowledged just that debate…

“An age-related increase in augmentation is consistent with evidence of poorer uterine function at older ages,34 longer labours34 and an increased incidence of prolonged labour,35 ,36 but the reasons for a steeper increase in augmentation with age in non-OU settings are unclear. It has been suggested that labelling of older women as ‘higher risk’ and/or heightened concern about the safety of older nulliparous women, particularly those who have required fertility treatment, may result in increased rates of caesarean section for non-medical reasons,20 ,32 ,33 ,37 and it is possible that similar factors affect midwives’ decision-making regarding transfer for failure to progress, or for other reasons. Intrapartum transfers from midwifery units in the Birthplace study have been shown to increase significantly with age in nulliparous women29 and, once transferred, women are ‘exposed’ to the higher intervention rates found in OUs.”  (Yangmei et al 2014)



Objectives To describe the relationship between maternal age and intrapartum outcomes in ‘low-risk’ women; and to evaluate whether the relationship between maternal age and intrapartum interventions and adverse outcomes differs by planned place of birth.

Design Prospective cohort study.

Setting Obstetric units (OUs), midwifery units and planned home births in England.

Participants 63 371 women aged over 16 without known medical or obstetric risk factors, with singleton pregnancies, planning vaginal birth.

Methods Log Poisson regression was used to evaluate the association between maternal age, modelled as a continuous and categorical variable, and risk of intrapartum interventions and adverse maternal and perinatal outcomes.

Main outcome measures Intrapartum caesarean section, instrumental delivery, syntocinon augmentation and a composite measure of maternal interventions/adverse outcomes requiring obstetric care encompassing augmentation, instrumental delivery, intrapartum caesarean section, general anaesthesia, blood transfusion, third-degree/fourth-degree tear, maternal admission; adverse perinatal outcome (encompassing neonatal unit admission or perinatal death).

Results Interventions and adverse maternal outcomes requiring obstetric care generally increased with age, particularly in nulliparous women. For nulliparous women aged 16–40, the risk of experiencing an intervention or adverse outcome requiring obstetric care increased more steeply with age in planned non-OU births than in planned OU births (adjusted RR 1.21 per 5-year increase in age, 95% CI 1.18 to 1.25 vs adjusted RR 1.12, 95% CI 1.10 to 1.15) but absolute risks were lower in planned non-OU births at all ages. The risk of neonatal unit admission or perinatal death was significantly raised in nulliparous women aged 40+ relative to women aged 25–29 (adjusted RR 2.29, 95% CI 1.28 to 4.09).

Conclusions At all ages, ‘low-risk’ women who plan birth in a non-OU setting tend to experience lower intervention rates than comparable women who plan birth in an OU. Younger nulliparous women appear to benefit more from this reduction than older nulliparous women.

Strengths and limitations of this study

  • The study was based on a large, nationally representative cohort of ‘low-risk’ women, with high-quality data collected prospectively.

  • The number of women aged over 40 was relatively small, so the study had limited power to explore effects in women over 40, particularly in non-obstetric unit settings.

  • Planned births in non-obstetric unit settings were combined; graphical plots indicated that this was reasonable but important differences between settings cannot be ruled out.

The paper can be read in full here

photo credit: Über Times  via photopin cc

1 comment for “Age, obesity and uterine contractility…

  1. lynette mayo
    June 16, 2014 at 4:44 am

    Hi Sara:
    I was interested in this topic because an acquaintance was induced, l am looking into this procedure done in England. I am English, naturalized US Citizen. Despite my gentle encouragement, she had this done. I was very disappointed? overall, l have read that a lot of English people know LITTLE? about the after effects of birth traumas? and being induced isn’t something routine, for the baby who suffers it? l am part of a support group for a rare illness (dercums disease). To my dismay, a lot of younger people with this are still having babies. Having been a health nut since the 1970’s, when l was treated by Alan Nitter, MD, “A New Breed of Doctor”, for Hyperglycemia, which was unknown in traditional medicine at that time. I have a strong background in Functional Medicine.

    Thanks to John Lennon, who told everyone, “Read the Primal Scream”, which l did. I did this in 1976 for a long time, it gave me a good quality of life. I went back to it when l got this diagnosis about a year ago. My point in all this, is: that a huge amount of people who did this therapy, from all over the world, where, ironically war babies?. Long story short. I got this disease, according to janov.A,
    because l was in-utero during a war. The baby gets massive amounts of stress hormones from a mother living in daily terror. I got this illness at age 69, l think because l had help dealing with psychological issues thanks to this therapy, and having a background in functional medicine. I read about this in “Life Before Birth.” , Janov won a prestigious award for this book, and he is considered to be an unsung hero of the 20th century, l would surely vouch for this. Other books on this topic, Imprints. His blog is astounding, written at age 89. “reflections on the human condition”, l think he did one on John Lennon?.He is on LinkedIn if you want to write to him? feel free to contact me.

    Lynette Mayo (age 71)

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