Restraint stress prolongs Diestrus phase of mouse Estrous cycle.

Globally, stress levels among women of reproductive age are rising, while fertility rates continue to decline. Despite this correlation, a causal link between stress and reduced fertility remains unclear. Experimental studies have shown that severe chronic stress can disrupt reproductive function, but the effects of mild stress, more representative of the daily stress experienced by most women, are still poorly understood. This study aims to identify how mild stress affects the mouse estrous cycle. Nineteen mice were vaginally lavaged daily one week before stress, during 3-day stress, and one week after stress. The mild stress paradigm consisted of two hours of repeated restraint stress each day for three days. Restraint stress disrupted the estrous cycle causing a longer cycle length in stressed mice, characterized by an extended duration in the diestrus phase. These findings suggest that even moderate stress perturbs normal reproductive cycling, potentially contributing to reduced fertility. This work highlights the need to further explore how everyday stressors may subtly impair reproductive health.