is birth necessary, the kinsey institute
© Olesia Bilkei

Dr. Sue Carter, Distinguished University Scientist and former Director of the Kinsey Institute, asks if birth is necessary, and if so, why?

Brave New World, Aldous Huxley’s 1932 dystopian novel, predicted a future in which humans would be created in test tubes, gestated in jars and “decanted” into independent existence. However, in the 21st-century foetuses created either in vivo or in vitro still must grow in utero, and be “delivered” through the process known as “birth.”

To this day birth remains both essential and mysterious. As Western medicine emerged over the last century, there has been interest in improving on “mother nature.” In the short-term, medically-managed births seemed more predictable and less dangerous. However, science is gradually discovering that avoiding or manipulating birth holds hidden risks for both mother and child.

Epidemiological studies show that surgical births are statistically associated with a host of maternal health risks, including maternal death and later sub-fertility in some women (1, 2). Postpartum depression and anxiety, which can occur in 15 to 20% or more of new mothers, is significantly more likely after a caesarean birth (3). It is estimated that the benefits of caesarean section outweigh the risks only in roughly 10 to 19% of births (4, 5). Despite recognition of the health advantages of vaginal births, caesarean section rates have almost tripled in the last three decades.

In the United States, roughly one in three babies are born by caesarean section with rates around 27% in the UK and Canada. Even higher rates are reported in China and Latin America. In private hospitals in Brazil, the rates of surgical birth reached a staggering 80-90%. What was intended as a method for dealing with birth emergencies, became increasingly “elective,” with consequences that are only now being appreciated.

Benefits of birth

Uterine contractions are facilitated by hormones, including the neuropeptide oxytocin. These contractions clear the infant’s lungs of amniotic fluid and facilitate breathing.

is birth necessary, the kinsey institute

Children born by caesarean section also are at risk for asthma and obesity, two epidemic disorders in modern life (6). The digestive system of a newborn mammal is sterile and requires colonization by friendly bacteria. Bacteria are acquired from the mother during passage through the vagina. Healthy bacteria also can be transmitted in colostrum and maternal milk, helping to prepare the baby to deal with the microbial environment it encounters at the time of birth.

As one example, Lactobacillus reuteri, a powerful probiotic bacteria found in human milk, has a variety of beneficial effects, including facilitating normal digestive function, wound healing and sociality. The health benefits of probiotic bacteria involve several systems, including the autonomic nervous system (vagus nerve), and are mediated in part by the neurohormone, oxytocin (7).

Cocktails for birth

Other interventions often accompany birth. Synthetic oxytocin (Pitocin or Syntocinon), may be used to induce or augment labour. However, these treatments, which increase the intensity of uterine contractions, also lead to increased pain. Pain medications, in turn, can inhibit the release of endogenous oxytocin and delay labour, eventually requiring more interventions, including additional exogenous oxytocin, and eventually a caesarean section. Opiates given to the mother can be detected in the infant’s urine 24 hours after birth. Some mothers given opiates during birth become drug-dependent. Furthermore, often added to the maternal cocktail are commercial antibiotics, which may disrupt healthy bacteria in the mother and child.


Oxytocin is a molecule best known for its role in female reproduction, as well as social behaviour and stress-coping. This same hormone stimulates oxytocin receptors in the intestine with direct consequences for neonatal digestion. In mouse models considered to be relevant to autism, animals genetically predisposed to show low levels of social behaviour and deficits in oxytocin pathways also have abnormal gut functions. These mice are especially vulnerable to disruptions in the microbiome, although normal behavioural and digestive functions can be restored with oxytocin (8).

The oxytocin system and the digestive biome may be especially important in explaining the benefits for the child of vaginal versus caesarean birth. Healthy bacteria and oxytocin can spare the baby from detrimental effects of birth-related hypoxia, reduce pain and stimulate maturation of the developing nervous system and lungs (9,10). Oxytocin also primes oxytocin receptors and facilitates social behaviour, especially in the face of stress.

Although most often studied in the context of birth and lactation, there is increasing evidence that oxytocin is a powerful anti-inflammatory and anti-oxidant (11), with the capacity to “educate” the developing immune system, protect against cancer, and support the functions of the microbiome. Under optimal conditions, oxytocin benefits virtually every tissue in the body. When oxytocin is absent, or when given in excess, these functions are disrupted, with effects that are not yet well understood.

“Now is the time to understand more”

Under conditions when a caesarean section is necessary, breastfeeding may be one natural way to partially compensate for the effects of surgery. Human milk supplies ideal nutrition, healthy bacteria, direct transfer of oxytocin and other vital hormones. For the mother, lactation encourages mother-infant interactions, helps protect against over-reactivity to the stress of child-rearing, and reduces the later risk of maternal breast cancer. Although the benefits are well accepted, lactation is more difficult after a surgical birth, and all postpartum mothers, and especially those who are nursing need support and knowledge.

An increasingly medicalised perspective on human life and especially fear of birth have encouraged the use of elective caesarean sections and other invasive birth interventions. Caesarean sections, in particular, can save lives, can appear to reduce uncertainty and may be financially profitable to health providers. However, there is also increasing evidence that vaginal birth has direct benefits for later physical and mental health in mother and child.

To quote the twice-honoured Nobel Laurate, Madam Marie Curie, “Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.” A deeper understanding of the biology of birth is necessary if we are to adequately evaluate alternatives, avoid mistakes and reduce fear.


Support for the research described here came from the National Institutes of Health, NICHD (P01 HD 07575) and the Fetzer Foundation.




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Director, Emerita and Distinquished University Research Scientist
The Kinsey Institute
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