For years, workers in hospital maternity wards have claimed an uptick in women going into labor during a full moon. Some studies have shown that correlation is possible, but other more recent ones have demonstrated no link. Overall, theories that lunar phases influence labor are still inconclusive.
Rumors exist of hospital emergency and maternity wards being busier during the full moon, but until recently, there's been no explanation as to why, or even whether this is true. Perinatal Education Associates reports that doctors, nurses, midwives and other childbirth professionals have asserted that they see a rise in volume during a full moon.
A 1986 French study published in the Journal of Obstetrics, Gynecology and Reproductive Biology studied millions of French births over several decades, and the results showed that more births tended to occur during the moon's descending phase, i.e., the period between the last quarter and the new moon. Fewer births took place in the ascending phase, in the first quarter of the moon.
An Italian study in 1994 showed the moon's influence on spontaneous deliveries is most felt on mothers who have given birth before. Deliveries studied over a three-year period showed a correlation to periods when there is a full moon present.
A 1998 study at Long Island College Hospital in Brooklyn, N.Y., showed no difference in spontaneous births that took place during the ascending phase or descending phase, and similarly no difference between the number of births that took place during the full and new moons. The study took place over the course of a year. The study's authors claimed that full-moon births are a "myth, not reality."
According to Baylor University biologist Paula Burch, Ph.D, barometric pressure may have more of an influence on labor rates than the phases of the moon. More babies are born when the barometric pressure drops, such as when a large storm passes through. Since barometric pressure, combined with the moon's gravitational pull, also changes the tides, this may explain the association with the moon and labor