In realtà, dall'articolo originale, la differenza è tra nullipare e madri:
In this nationally representative, cross-sectional study of reproductive age US women, having had at least one live birth was associated with shorter telomere length compared with no live births. This association persisted even after adjustment for age, race/ethnicity, education level, income-to-poverty ratio, early age at menarche, BMI and smoking status. As shortened telomeres are associated with cellular aging and increased risk of several chronic diseases as well as overall mortality (Cawthon et al., 2003), further investigation is warranted.