Women who wait to have a baby until after they have established their career are more likely to suffer from post-natal depression, scientists say。
Older mothers are more likely to 'over-prepare' for their first-born and struggle when things don't go as planned, a study suggests。
The findings are of great significance in the UK, where an increasing number of women are choosing to delay motherhood until they are more financially secure。
Research leader Silje Marie Haga, from the University of Oslo, in Norway, said: 'There are some indications that older, first-time mothers are vulnerable to postpartum depression, perhaps because they are used to being in control of their own lives: they have completed a long education and established a career before they have children。
'But you can’t control a baby; on the contrary, you have to be extremely flexible。
'Several of the women I interviewed said themselves that this contributed to the huge feeling of letdown when things did not turn out as they had planned.'
In the UK, there were 26,976 babies born to mothers of 40 and over in 2009, compared with 9,336 in 1989, according to the Office for National Statistics figures。
The latest study analysed surveys from around 350 new mothers as well as in-depth interviews with 12 first-time mothers. It found 16.5 percent reported suffering from depression for up to six months after giving birth。
Ms Haga said the interviews highlighted a number of risk factors apart from biological ones。
'It’s not the need for control in itself, but rather the failure to achieve specific expectations that can trigger a depression,' she said。
'In contrast, women who take a more relaxed approach to motherhood with more undefined expectations cope better with unexpected challenges.'
Other women struggled after the delivery left them 'feeling like a failure'。
One new mother told Ms Haga she struggled after having an unplanned caesarean section: 'That wasn’t how I was supposed to have a baby. I was so tired and so disappointed, I was so sad,' she said。
'I hadn’t been able to give birth to my baby; someone had to do it for me.'
'In my study the women who had the greatest need for control often had the strongest wish to have a natural birth,' Ms Haga noted。