Is night shift work safe during pregnancy?

What does the evidence say about night shift work during pregnancy?

1. Among 4,970 births to Swedish healthcare employees, more than 25 night shifts in the first trimester was linked to higher odds of preterm birth (odds ratio 1.62), and working three or more consecutive nights more than eight times raised it further (odds ratio 3.01). 1
2. A large register-based cohort of 16,501 pregnancies found no elevated preterm birth risk among night workers at all, with preterm birth at 5.2 percent in night workers versus 5.1 percent in day workers, and no relationship to the number, duration or spacing of shifts. 2
3. Pooling the wider literature, shift or night work carried an odds ratio of 1.63 for preterm birth, rated as moderate evidence of a positive association, alongside long working hours at 1.44. 3
4. An earlier meta-analysis put the shift work estimate lower, at a relative risk of 1.14 for preterm delivery, and found no meaningful association with a small-for-gestational-age baby. 4
5. Quick returns, meaning less than 28 hours between the end of a night shift and the start of the next, showed raised odds of preterm birth when they happened more than 18 times (odds ratio 2.42), which points at recovery time as the modifiable piece. 1

Is night shift work safe in each trimester?

• First trimester. The Swedish healthcare cohort found its clearest signals in the first trimester, specifically for more than 25 night shifts and for runs of three or more consecutive nights. If your rota is negotiable, this is the quarter to spread the nights out.
• Second trimester. Nausea usually eases and sleep is often at its best, which makes this the most workable stretch for night work. Protect the daytime sleep block rather than trying to run errands on it.
• Third trimester. Long weeks carry more weight now: working over 40 hours in the third trimester was linked to roughly double the odds of preterm birth in the Swedish cohort. Cutting hours may matter more than cutting nights.