Packing for Mars: The Curious Science of Life in the Void

by Mary Roach

Rats who’d spent two weeks in space had fewer, and weaker, uterine contractions. In Ronca’s view, this is a dangerous difference. Contractions play an important role in a newborn’s adjustment to life outside the womb. The compressions of vaginal birth cause a huge release of stress hormones in the fetus; these are the same fight-or-flight hormones that fuel feats of extreme strength in adults. “This hormonal surge appears to be very important for getting physiological systems moving. All of a sudden a newborn has to breathe on its own, it has to figure out how to suckle from a nipple. If there aren’t enough contractions, the hormone release is smaller and the fetus has a harder time.” Studies have shown that infants born via planned C-section, with no contractions—as compared to those delivered vaginally—have a higher risk of respiratory distress and high blood pressure, a harder time expelling lung fluids, and delayed neurodevelopment. In other words, stressing an infant appears to be part of nature’s plan. (For this reason, Ronca is also not an advocate of water births.)