When I was pregnant, I was always told to think happy thoughts, banish negativity and surround myself with cheerful vibes. If I did, they said I'll have a happy baby.

Rubbish old wives tale? Not entirely.

According to a new study, a mom's mood during her pregnancy greatly affects her baby's behavior. In particular, they found that the mother's emotional state had an effect on her baby's regular sleeping and waking patterns, known as circadian rhythms.

Babies whose mothers experienced depression any time before they became pregnant, or developed mood problems while they were pregnant, are much more prone to having chaotic sleep patterns in the first half-year of life than babies born to non-depressed moms, the team has found.

For instance, infants born to depressed moms nap more during the day, take much longer to settle down to sleep at night, and wake up more often during the night. It's a baby form of the insomnia that millions of adults know all too well.

Not only does this add to parents' sleepless nights, but it may help set these children up for their own depression later in life.

In my experience, it doesn't seem like this was the case at all. I was definitely more positive, more bubbling, more excited, more cheerful during my first pregnancy, but it's my second-born who had a splendid sleeping patterns. Since she was two weeks old, she would sleep for 11 hours almost through the night, just waking for a feed once or twice, but going right back to sleep after feeds.

While I do believe in fetal programming, i.e., the conditions in utero has a big impact on the physiology of the baby later on in life, I'm sure that a mother's emotional state during pregnancy is only one of the factors influencing a baby's sleeping patterns.