The Lunar Effect on Delivery and Other Birth Outcomes in Rural Zambia

Objective: It is a widely held belief that the period of a full moon is associated with higher birth rates compared to periods when the moon is not full. We investigated whether more births occurred during a full moon in a rural African population. Design: Data collected from 42 clinical sites in rural Zambia associated with the Better Health Outcomes through Mentoring and Assessment (BHOMA) Study were evaluated. We compared the proportion of pregnancies born during a full moon to the proportion that would be expected if there were no association. Main outcomes: Proportion of births during the full moon. Measures: Demographics and birth outcomes. Results: A total of 10,127 women delivered at a participating site between 8 December 2010 and 19 August 2015. Mean maternal age was 25.1 years (standard deviation [SD] 6.4 years), mean maternal weight 62.7 kg (SD 13.9 kg), 14.4% were HIV seropositive, and 3.7% were syphilis positive. The mean birthweight was 3032 g (SD 0.5 g); 49.6% newborns were female, and 1.48% were stillborn. There was a full moon during 70 of the 1715 days under observation. In the absence of an association, we would expect 70 / 1715 (4.08%) of births to occur on these days. We observed a total of 434 deliveries (4.29%; 95% Confidence Interval [CI]: 3.89%, 4.68%) during these 24-hour periods. Thus, an association between the full moon and higher delivery rates was not observed (p=0.87). An additional analysis, where the entire lunar cycle was divided into 8 equal bins, also yielded no association. Finally, we did not identify any other birth outcomes that were associated with lunar cycle (birthweight, stillbirth, gender, or congenital malformation). Conclusions: In this large, rural population, we found no evidence of a lunar effect on delivery or adverse birth outcomes. These results refute a common belief and should provide assurance to managers who opt to ignore lunar cycle when scheduling midwife staffing of rural clinics.