Explanations of the obstetric dilemma: evolutionary conflict exacerbates health problems in pregnancy and childbirth

This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. In excellent recent work, Webb and colleagues challenged the so-called “obstetric dilemma”—the long-standing hypothesis that human childbearing is particularly dangerous because we have a narrow pelvis but large infant heads (we are bipedal and smart). They showed that humans and chimpanzees have a comparable fetal-pelvic squeeze. What, then, causes risky childbirth in humans? Webb and colleagues describe a gradual series of physical obstetric compromises: e.g., our contorted birth canal allows bipedal movement but requires the fetus to rotate during birth. We propose an additional obstetric compromise between the evolutionary interests of mother and fetus, who experience genetic conflict over resource allocation. The fetus manipulates maternal vasculature to boost resources flowing to the placenta, benefiting itself but increasing the risk of maternal hypertension and hemorrhage. Following Haig, we suggest that maternal-fetal conflict harms human mothers more than other mammals because our cooperative infant care permits more damage to maternal health (when it grants some resource benefit to the fetus). https://doi.org/10.32942/X2KS7G Anthropology, Biological and Physical Anthropology, Ecology and Evolutionary Biology, Evolution, Genetics, Life Sciences, Maternal and Child Health, Medicine and Health Sciences, Translational Medical Research evolution, maternal-offspring conflict, obsetric dilemma, pregnancy, birth, Maternal Health Published: 2025-03-03 11:44 Last Updated: 2025-05-07 08:01 CC BY Attribution 4.0 International Conflict of interest statement: None Data and Code Availability Statement: Not applicable Language: English