Arline Geronimus, a professor at the University of Michigan School of Public Health, coined the term “weathering” for how this continuous stress wears away at the body. Weathering “causes a lot of different health vulnerabilities and increases susceptibility to infection,” she said, “but also early onset of chronic diseases, in particular, hypertension and diabetes” — conditions that disproportionately affect blacks at much younger ages than whites. It accelerates aging at the cellular level; in a 2010 study, Geronimus and colleagues found that the telomeres (chromosomal markers of aging) of black women in their 40s and 50s appeared 7 1/2 years older on average than those of whites. Weathering can have particularly serious repercussions in pregnancy and childbirth, the most physiologically complex time in a woman’s life. Stress has been linked to one of the most common and consequential pregnancy complications, preterm birth. Black women are 49 percent more likely than whites to deliver prematurely (and, closely related, black infants are twice as likely as white babies to die before their first birthday). Here again, income and education aren’t protective.