For Mammals, Difficult Childbirth Is the Norm

Human childbirth has long been considered especially risky, owing to upright bodies with large brains moving through narrow birth canals, but it turns out we're no outliers: difficult births are widespread among placental mammals, according to a new study. The review from Nicole Grunstra of the University of Vienna finds similar birth complications and maternal deaths in wild and domestic species ranging from cows and elephants to seals and deer—in some cases, at rates on par with humans living without modern medical care, per a release. They occur among non-bipedal animals and those with small brains. Even whales and dolphins can face stuck calves, despite their lack of a bony pelvis.

The research, published in Biological Reviews, signals that this is a broad biological pattern that evolution hasn't fixed because there are tradeoffs. Larger newborns often fare better after birth, but they're harder to deliver, leaving a narrow margin between being too small to thrive and too big to safely pass through the birth canal. Species that have litters, like dogs and pigs, face a different balancing act: very small litters mean larger, harder-to-birth animals, while very large litters increase the risk of fetuses blocking each other's exit. The study concludes that, as challenging as it is, "human childbirth is not extreme in a biological sense," per Earth.com, and that we share risks with other mammals, including for first-time and smaller mothers.