Shift work and your reproductive health

A 2023 meta-analysis (Li et al, Heliyon) confirmed what the Nurses' Health Study II (Lawson et al 2011, Epidemiology) had already shown: rotating and night-shift workers have measurably higher rates of irregular cycles, longer time-to-pregnancy, and increased risk of early miscarriage.

This is especially relevant for many South Asian women working in NHS nursing and care, retail and hospitality, late-evening family business hours, or roles that do not respect a 9-to-5. It is not a moral issue, it is circadian biology.

Your internal clock regulates the timing of LH and FSH release from the pituitary, which drives ovulation. Sleep-wake cycles control when melatonin rises and falls, and melatonin itself accumulates in the follicular fluid around developing eggs, where it provides antioxidant protection. Repeated disruption scrambles these signals.

Women sleeping fewer than 6 hours per night have significantly higher odds of abnormal cycle length (OR 2.1, 95% CI 1.2 to 3.7) (Lim et al, 2016). This does not mean every shift-worker will struggle, but if your cycles are already irregular, shift work is a relevant modifiable factor.

Protect sleep opportunities whenever you have them, blackout curtains or a good eye mask, earplugs, cool room, phone on do-not-disturb. On rest days, try to keep a consistent sleep window rather than oscillating wildly.

Request fixed shifts rather than rotating where your employer allows, fixed-pattern shift work is less disruptive than rotation. Morning exposure to daylight on days you can (a short walk first thing) helps re-anchor your circadian rhythm.

Note on melatonin: melatonin above 1 mg is prescription-only (POM) in the UK. Do not self-medicate with high-dose melatonin bought online. Your doctor can discuss options if sleep is significantly disrupted.