Maternal wellbeing could be boosted by understanding postpartum sex through ‘evolutionary lens’

The pressure some new mothers feel to resume sex after childbirth could be eased through an understanding of evolutionary theory. 

Postpartum sexual dysfunction, which includes lower libido, arousal or struggle to orgasm as well as dyspareunia – pain during intercourse – affects the majority of sexually active women, with 85.7% having experienced dyspareunia when first resuming postpartum sex.

For many, this is a cause of distress borne of multiple factors such as depression, stress, exhaustion, feeling unattractive, negative childbirth experiences, perineal damage incurred during labour and the hormonal changes associated with breastfeeding.

However, researchers argue that it could be a form of adaptive evolution that helps reduce the probability of further conception and extends the intervals between births, leading to better health outcomes for both mothers and children.

Writing in the journal, Evolution, Medicine, and Public Health, they note there are multiple barriers to conception postpartum, with diminished libido coupled with painful intercourse reducing the likelihood that postpartum women resume sex, with suppressed ovulation and vaginal dryness, reducing the chance of fertilisation should sex occur.

The researchers say that having multiple barriers to sex and fertilization could reflect the phenomenon known as ‘sexual conflict’, when the evolutionary interests of males and females do not align.

Reproductive frequency is described as a major arena for sexual conflict, with optimal mating rates for males tending to be higher than for females.

The researchers say this reflects the evolutionary idea that males maximise their reproductive fitness (number of offspring) by having more sex, while females maximise their fitness by investing more in each reproductive event.

In the postpartum period, this potentially sets up an evolutionary conflict, with selection favouring males who can bias sexual interactions in their favour (and resume postpartum sex earlier), while selection on females favours those who evolve to counter male interests (and extend inter-birth intervals).

Previous studies have reported that women feel pressure to have sex postpartum, and data shows an increased risk of sexual violence during this period, which could be linked to the lower libido of new mothers.

Professor David Hosken, an evolutionary biologist at the University of Exeter, said: “Reports that new mothers are under pressure to resume sex, and may be more vulnerable to sexual violence, is consistent with sexual conflict over postpartum sex at some point in our evolutionary history.

“But even if sexual conflict does not help drive postpartum changes to sexual function, it seems likely that postpartum sexual disruption could be adaptive.”

Dr Ruth Archer, a lead author of the study from the University of Ulm in Germany, added: “Understanding sexual dysfunction through an evolutionary lens could, we argue, promote help-seeking behaviours, ease feelings of ‘guilt and failure’ due to libido declines and adjust new parents’ expectations about resuming sex.

“This is a discussion that could adjust wider societal expectations, promote maternal well-being and relationship satisfaction as well as ease some of the pressure on new mothers, wherever that pressure might come from.”

“Sexual Conflict over Sex – An Underappreciated Consequence of Childbirth?” is published in the journal Evolution, Medicine and Public Health.