Dear Editor,

Postovulatory aging would occur to impair the oocyte quality in a time-dependent manner if ovulated oocytes are not fertilized within the optimal timing in the oviduct or in the dishes (Trapphoff et al., 2016), which might result in the early pregnancy failure in vivo and adverse outcome of assisted reproductive technology (ART) in vitro (Nagy et al., 1993; Wilcox et al., 1998). However, the effective approaches to preventing the postovulatory aging-induced oocyte deterioration are still underexplored. We recently reported that supplementation of nicotinamide mononucleotide (NMN), a synthetic precursor of NAD+, which is an essential cofactor for enzymes’ functioning in almost all critical cellular metabolic reactions (Imai and Guarente, 2014; Canto et al., 2015), reverses the declining quality of maternally aged mouse oocytes (Miao et al., 2020).