I don’t know that many successful working mothers in investment banking – I’d like to think I was one once, before I opted out.

What discourages women from entering the profession – and then sticking with it? The most obvious answer is the hours.

All junior bankers – male and female alike – tend to put in “face time”, working hard and long, simply to show that they can do it. Under-promising and over-delivering are the watchwords.

Years ago, when I was an analyst, my father came down to my office building at 3am trying to find me as I wasn’t answering my office phone. He (and a security guard) finally unearthed me huddled with another female analyst in a conference room. I hadn’t had dinner and had just worked straight through. My deadline wasn’t until lunchtime, but I wanted to make sure the presentation draft was on my associate’s desk when he arrived in the morning.

I wasn’t unusual. At the start of their careers, many women tend to work harder than their male colleagues. They need to prove that they belong to the club. Men, to my mind, don’t have the same overwhelming urge to prove themselves. They simply assume they’re in the right place.

However, once women have children, their priorities shift.

Mothers want to see their children. After work, they want to relax with a glass of wine in front of the TV, or with a good book. They also tend to bear the brunt of childcare and household chores.

Many fathers, by comparison, often continue to work all hours of the day and night. And when they’ve finished work, they might go to the pub rather than going home. This helps their careers as they’re informally networking with their peers.

But does the fact that women want to go home at 6pm (or 7pm, or 8pm) mean they’re less productive than their male counterparts? Not necessarily. A lot of women work incredibly hard to get everything done (and done well) so that they can leave when they need to.

Equally, women who work part time or flexibly, often put in additional hours at home. They feel guilty for not being in the office, so often check emails and voicemails and call into the office to check that everything is OK. And it buys loyalty. Most women are far less likely to leave their employer if they feel that they have been well treated through pregnancy, maternity leave and returning to work.

I don’t want to minimise the challenges of managing a working mother – leaving at 6pm may not suit the rest of the team, clients don’t always fit in to her schedule, children fall ill, there are endless school concerts and sports days. Someone with constraints – be it motherhood, a scheduled team sport, a theatre group, whatever – may not fit into every job description. But don’t automatically assume that mothers are less productive – because in my experience, they’re not.

Anneke de Boer is a former managing director of Morgan Stanley’s fixed income business in London. She retired in 2006.