Scientists at the Yale School of Public Health examined 1.8million births and found that rates dropped by 11.3% on October 31.
The New Scientist reported that the decline in deliveries on Halloween applied to natural births as well as scheduled caesarean and induced births.
The researchers also found that births on Valentine’s Day jumped by 5% compared with a week on either side.
Rebecca Levy, who led the research, said the findings were evidence that women appeared to be able to apply some control to birth timing.
She said: “The study raises the possibility that the assumption underlying the term “spontaneous birth”, namely, that births are outside the control of pregnant women, is erroneous.
“We know that hormones control birth timing, and mothers do often express a desire to give birth on a certain day but the process that allows those thoughts to potentially impact the timing, we don't know.”
The team examined almost 2m births in the US between 1996 and 2006.
She added that mothers perhaps subconsciously wanted to avoid Halloween because of its associations with death and evil.
Levy said: “It evokes fear on some level.”