Women trying to start a family who find themselves constantly reaching for a stress ball, take heed: All that extra anxiety may be keeping you from conceiving, AFP reports.

A study carried out by researchers from the University of Louisville and published in the Annals of Epidemiology journal says that ladies who found it harder to chill out during their peak ovulation time were 40% less likely to get pregnant than in other less-stressful months—and that women who reported more stress than their counterparts were 45% less likely to conceive, per a press release.

The researchers followed 400 sexually active women no older than 40 through up to 20 of their menstrual cycles or until they conceived, while the subjects kept diaries logging everything from alcohol and caffeine use to how often they had sex and what kind of contraception they used.

The subjects also noted their daily stress levels on a scale from one to four—and the researchers found, after controlling for those other factors, that during peak ovulation time (around Day 14), women who reported the highest levels of stress registered that drop in fertility, and only during that peak ovulation time.

Perhaps not as surprisingly, women who became pregnant experienced a stress spike at the end of the month in which they conceived, with researchers guessing the extra stress was from finding out they were with child or due to the hormone changes in their bodies.

Study co-author Kira Taylor says she hopes the study will prove to be a "wake-up call," both to doctors and patients, that mental wellness is just as important as nutrition and other physical self-care for women trying to get pregnant.

This article originally appeared on Newser: Want a Baby? Take a Chill Pill