You know the saying "don't worry, be happy"? It could be one of the best advice out there for women who are trying to conceive.

Women may have a more difficult time becoming pregnant when they're feeling stressed, according to a new study by researchers at Oxford University and the US National Institutes of Health, who were looking into how stress factors into the chances of pregnancy for normal, healthy women trying for a baby.

For this study, 274 healthy women, aged 18 to 40 who were trying to conceive, had their ovulation cycle charted and provided saliva samples to test for levels of alpha-amylase (a biomarker for stress associated with the body's 'fight or flight' reflex).

The results showed that women with high alpha-amylase levels were less likely to conceive than those with low levels: Women with the highest levels of alpha-amylase had an estimated 12 percent lower chance in getting pregnant each cycle compared to women with the lowest concentrations.

This is the first time any study has seen a difference in chances of pregnancy associated with a biological measure of stress. And the conclusion is pretty clear: If you're trying to conceive, learning to de-stress can't hurt. "The findings support the idea that couples should aim to stay as relaxed as they can about trying for a baby," says Dr Cecilia Pyper of the National Perinatal Epidemiology Unit at the University of Oxford.

Here are some ways to keep stress away:

Calm down

When tension heats up, find ways to wind down: Play soothing music, run hot water and have a long soak in the tub, call a close friend and vent. "In some people's cases, it might be relevant to look at relaxation techniques, counselling and even approaches like yoga and meditation," says Dr Pyper.

Walk it off

Yes, exercise burns off stress. "Exercise can provide an outlet for negative energy such as anger and hostility, explains Stephanie McClellan, M.D., co-author of So Stressed, "releasing negative emotions in a healthy way." Take a brisk walk around your block, ride the stationary bike, swim a few laps, any activity that gets you moving for 30 minutes everyday.

Breathe

"Deep breathing has a calming and centering effect, and you can do it anyplace, anytime for a quick fix for acute stress," says McClellan. When you encounter a stressful situation, try this technique: Close your eyes and take slow, deep breaths and count to 100 to calm down.

Don't sweat the small stuff

Try not to get worked up over life's little annoyances, like the cab driver who cut you off, or the woman in front of you who hogged the ATM machine. They're not worth spoiling your mood for, really.