“Future research is needed to identify the process,” write the authors, but it appears that pregnant women have some control over when they give birth. A study of birth incidence on Halloween and Valentine’s Day, by public health scholar Becca Levy and colleagues, showed that spontaneous births dipped on the former and rose on the latter.

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The authors suggest that this contributes to growing evidence that culture influences birth timing. Women’s bodies resist giving birth on a day associated with fright and death, but give into birth on a day associated with love. The authors recommend extra staffing on obstetric wards on Valentine’s Day and sending a few more doctors and nurses into the streets on Halloween.

Lisa Wade, PhD is an Associate Professor at Tulane University. She is the author of American Hookup, a book about college sexual culture; a textbook about gender; and a forthcoming introductory text: Terrible Magnificent Sociology. You can follow her on Twitter and Instagram.