(MONEY Magazine) – How does Mother Nature hedge her bets when the economy heads south? It could be by stocking up on baby girls. According to a new study by Ralph Catalano, professor of public health at the University of California at Berkeley, traumatic cultural events like economic downturns may result in fewer births of boys.

Catalano analyzed birth data in East and West Germany from 1946 to 1999. In 1991, a period of economic upheaval in East Germany, over 800 fewer boys were born than expected. When conditions improved in 1992, the birth ratio of boys to girls returned to normal. The fiscally happy West Germans saw no change.

Blame biology: Research shows that male fetuses are more likely to be affected by stress hormones and miscarried, or are less likely to be conceived at all due to spooked sperm. One thing's certain--stressing out your partner won't help picky parents determine the baby's sex. "This only works at the herd level," says Catalano, laughing. --ELLEN MCGIRT