Women who postpone pregnancy until they have established their career are more likely to suffer post-natal depression, scientists warned.

Researchers suggest that this is because older mother s are more likely to ‘over-prepare’ for their fist-born and struggle when things don’t go as planned.

“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,” lead researcher Silje Marie Haga, from the University of Oslo, in Norway, said in a statement released on Monday.

The findings are significant in the United States and other developed countries, where an increasing number of younger women are postponing motherhood in much greater numbers than older women.

The average age of first-time mothers in the U.S. jumped from 21.4 in 1970 to 25 in 2006, according to a report in the August 2009 edition of National Center for Health Statistics Data Brief, and the number of first births to women aged 35 and older increased nearly eight times since 1970.

According to data released in December 2010 by the Centers for Disease Control and Prevention, in 2009, the birth rate for women aged 20 to 39 declined, while the birth rate for women aged 40 to 44 actually rose by 3 percent and the birth rate for women aged 45 to 49 remained unchanged from 2008.

The latest study analyzed surveys from around 350 new mothers as well as in-depth interviews with 12 first time mothers and found that 16.5 percent of the participants reported that they suffered depression for up to six months after giving birth.

Apart from biological risks, Haga said that the interviews underlined a number of other risk factors associated with later births.

“Having very clear expectations and a great need for control is a risk factor. Those who prepare themselves to a very high degree for how life with the child will be have a hard time when things do not go as planned,” Haga said.

“So it’s not the need for control in itself, but rather the failure to achieve specific expectations that can trigger a depression. In contrast, women who take a more relaxed approach to motherhood with more undefined expectations cope better with unexpected challenges,” she explained.

One new mother told Haga in an interview that 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 had told Haga. “I hadn’t been able to give birth to my baby; someone had to do it for me.”

Haga noted that the women in the study who had the greatest need for control typically had the strongest wish to have a natural birth.

Difficulties with breast feeding can also trigger post-natal depression because of the societal pressure to choose breast over bottle, she added.

Researchers said new mothers need understanding as well as practical and emotional support, especially from her partner.

Haga notes that it is common that women will experience postpartum blues three to four days after birth, and in some cases it can last longer, which may be a sign of postpartum depression, which is similar to other kinds of depression with feelings of hopelessness, sadness, exhaustion and sleep problems even when the child is asleep.

“These women are unable to enjoy having a baby. Being depressed at precisely this period is an extra emotional burden to bear because of expectations that you should be happy,” Haga said, and often times these women are hesitant to ask for help because they think that there is a stigma attached to depression.

Haga stresses that she is not warning women against postponing pregnancy. However she said that it is vital for women to be aware of the latest findings.

The findings are published in the Scandinavian Journal of Caring Sciences.

Researchers are currently developing a web-based program with a mental health center in Norway that will monitor pregnant and new mothers from the 22nd week of pregnancy and up to six months after the birth. Haga hopes that they program will provide support for women during this sensitive period and potentially prevent postpartum depression.