Fertility After 35 May Not Just Be About Eggs, Scientists Say

Fertility after the age of 35 is frequently associated with declining egg quality and reduced ovarian reserve. However, recent research indicates the uterus may also be a crucial factor. A study in Cell Host & Microbe reveals that changes in the uterine microbiome, the bacterial community within the womb, could impact the uterus's receptivity to an embryo.

Lead author Rong Li, a physician at Peking University Third Hospital in Beijing, China, explains that while fertility declines after 35 have traditionally been linked to a diminished ovarian reserve and poor embryo quality, the endometrium's health also plays a significant role.

The study examined endometrial samples from 149 women undergoing infertility treatment, aged 20 to 45, split into three age groups: under 30, 30 to 35, and over 35. Younger women exhibited higher levels of Lactobacillus gasseri, a specific strain of bacteria, in the endometrium compared to the older groups. Notably, L. gasseri decreased with age. The research discovered that the diversity of overall microorganisms remained consistent across age groups, but particular species, like L. gasseri, varied considerably.

One surprising finding was that pregnancy rates did not differ significantly between age groups, but women who conceived had higher endometrial levels of L. gasseri than those who did not. Laboratory tests showed that L. gasseri possesses antioxidant and anti-inflammatory properties and adheres strongly to endometrial cells. Moreover, a compound produced by the bacterium, EPS, helped safeguard human endometrial stromal cells from aging.

In experiments with older mice, treatment with EPS from L. gasseri increased embryo implantation rates.

These preliminary findings suggest that for those attempting conception after 35, the discussion may need to encompass the uterus's readiness to support implantation, not just the ovaries and eggs.