In December 2016, a BBC News item (Briggs, 2016) summarised an academic article by a team of Austrian theoretical biologists with the headline: ‘Caesarean births “affecting human evolution”’.
According to the biologists (Mitteroecker et al, 2016), fetopelvic disproportion—where the fetal head is too big to pass through the maternal pelvis—accounts for most cases of obstructed labour in humans. The authors note that women with narrow pelvises would not have survived birth a century ago, and suggest that the increasingly regular use of caesarean section (CS) has resulted in an evolutionary increase of fetopelvic disproportion rates by 10–20%.
Given the media impact that ensued when the story was reported, one might infer that the relationship between CS and evolution was being aired for the first time. However, a 2003 paper—citing CS rates of around 22% in England and Wales—suggested the reason for humans' poor performance during natural childbirth is that cultural evolution has surpassed biological evolution. According to Liston (2003: 560), dietary habits favouring sugar and fat over protein, less exercise and changes in reproductive behaviour have contributed to primigravid women being typically shorter, older and fatter than is ideal for first childbirth, yet ‘some audits… have ignored these factors and their importance is not widely appreciated by either the medical professions or the general public.’
Trevathan and Rosenberg (2014: 164) consider that CS rates in parts of the world of more than twice the World Health Organization's recommended rate of 15% ‘probably reflect more than medical necessity’. While acknowledging that CS has saved the lives of millions of women and infants, they also cite studies recording CS-associated risks, including sepsis and death, haemorrhage, pulmonary embolism, and compromised breastfeeding and bonding. The authors state that tocophobia (fear of birth) is often given as a reason for choosing CS, and they highlight an evolutionary perspective which argues that ‘fear and the deeply rooted need for assistance during birth can often be alleviated with emotional support such as provided by doulas, thus avoiding unnecessary risky and costly CS.’
Current evidence suggests that the continued relatively high rates of CS are contributing to an evolutionary trend towards higher rates of fetopelvic dis proportion. But it is unlikely that long-term trends in evolutionary biology weigh heavily on most pregnant women's minds when faced with concerns such as how they would prefer to give birth.
Expert opinion, as is often the case, is divided. Gee (2015: 359) states: ‘…any denial of choice, providing the woman has the capacity to make a reasonable decision is passively paternalistic.’ Meanwhile, Easter (2015: 359) argues against CS on demand— ‘we argue for tailored support and evidence-based information for women requesting a CS’ and highlights cost implications, citing the estimation that ‘every 1% reduction in CS could save the NHS ~£5 million.’
At a time of economic austerity, these cost implications of CS are valid. The extent to which cost considerations might influence the actions of individuals in a way that may be harmful was raised by Walker (2016) who, as senior coroner for the Northern District of Greater London, opened an investigation on 9 July 2015 into the death of 5-day-old Kristian Jaworski. Kristian's death was thought to have been due to asphyxia ‘as a consequence of prolonged and extended instrumental delivery.’ Despite the mother having been advised to ask for a CS because of problems in a previous pregnancy, according to Walker (2016) ‘there was a presumption in favour of vaginal delivery based partly [on] cost.’
Some contend that health professionals—by medicalising pregnancy, sidelining homebirth and engaging in practices such as episiotomies—have been, literally, instrumental in making the natural process of vaginal birth more into a medical ordeal. If that is the case, then a woman who chooses to have a CS can hardly be condemned by those same health professionals. On the other hand, it could hardly be counted as a victory if near-universal CS were to become the norm.
At a time of competing birth ideologies, it seems that evolution will have a role to play—not least in how we view CS.