Members of the upper social classes tend to engage in INDIVIDUAL sports more frequently than members of the lower classes. The upper class people are wealthy and they like to ski, play tennis, go for boating and enjoy leisure time. They can go for golfing and spend a lot on their leisure activities.
I believe the answer is: <span>Humanize
During the childbirth, women most likely experience the most excruciating physical pain that they ever felt in their life, followed by mental stress and pretty high chance of death.
Medical workers and encouragement from a partner, would reduce all negative things above and increase the chance of successful childbirth.</span>
Diseases, Weather, and Food Sources.