Logically it may be assumed that the more children a mother has, the more stressed out she will be, but a new study has revealed that this is not the case.

In fact, mothers who have three children are the most stressed out - even more so than those who have four, according to a Today.com survey of 7,164 U.S. mothers.

The study found that while transitioning from two to three children is overwhelming for parents because it means they are outnumbered, mothers tend to 'let go' once they reach four children.

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Overwhelming: A study has found that three children is the most stressful number to raise, since the jump from two to three - which sees parents suddenly outnumbered - is a struggle to cope with

New York-based psychiatrist Dr Janet Taylor - whose own four children, including a set of twins, range in age from 19 to 25 - explained why four kids are easier to handle than three.

As far as perfectionism is concerned, 'there's just not enough space in your head' once you have at least four children, claims Dr Taylor.

Plus, she asserts: 'The more children you have, the more confident you become in your parenting abilities. You have to let go.'

Obsessively making the house baby-proof, for example, becomes less of a priority after the third child. 'It just gets to be survival!' she joked.

Baltimore, Maryland mother Jill Smokler, 35, a blogger and the author of Motherhood Comes Naturally (And Other Vicious Lies), has three children aged five, seven and nine, and agrees with the findings.

'Going from one to two was an easy, breezy transition,' she explained. 'Two to three, everything was turned upside-down.'

The reason? 'You only have two hands!' she exclaimed, noting that not having enough hands to hold onto each of them while crossing the street was a cause of extreme stress.

' Going from two to three children, everything was turned upside-down!'

Indeed, when mothers were asked to rate their stress level on a scale of one to ten, the average number was a whopping 8.5.

While children are a lot to handle, it would appear that a large part of the stress mothers experience is self-induced.

According to the survey, 75per cent of moms stress more about the pressure they put on themselves than the pressure felt from others.

What's more, 72per cent admitted they often get stressed out about stress itself.

For 50-year-old Karen Hobert Flynn, from Middletown, Connecticut, going from three to four children taught her to find ways to unwind by herself, something moms often don't make time for.

Perks of four: Karen Hobert Flynn (second left), who has four boys aged 11 to 16, says that an even number is easier to handle, since each child automatically has a playmate

'Instead of making the perfect lunch for your kids, go for a walk by yourself,' she advises. 'Even if it's just ten minutes, take some deep breaths and focus on what you need.'

Another way to decompress, the mother-of-four says, is to remember that it's important to be able to say no sometimes.

When her boys - now aged 11 to 16 - were growing up, she maintained her sanity by allowing only one after-school activity per child.

' The more children you have, the more confident you become in your parenting abilities'

'You can do Boy Scouts or a sport. We didn't do five sports,' she said, adding that this restriction didn't seem to limit her sons, since they all play competitive team sports now.

She also explained that having four children has its particular perks, such as the fact that with an even number, each child has an automatic playmate.

What's more, with a big family, the household is always exciting. 'We have a critical mass,' she said. 'Kids in the neighborhood would want to come here because it's an immediate party.'