Lean in, choose the right man, have children in your forties, have children in your twenties. Women are inundated with advice on how to “have it all” and successfully juggle career, marriage and kids.

Now a new book suggests the trick is to get up an hour before everyone else in the family and do more chores on the school run. Samantha Ettus, author of The Pie Life, has more bad news for weary working mothers: it is not enough to have a job and look after children. They need to stay interesting by keeping up with their hobbies, friends and exercise.

She has also fuelled controversy both here and in her native US by warning mothers that they will be “bored and unfulfilled” if they quit the world of work altogether.

No doubt many mothers with young children feel perfectly happy and fulfilled while their children are young — but it won’t last, she predicts.

“It might make you happy right now, but the baby years are short and the rest of life and a career are long. When the kids go to school you will want to go back to work and the stats show there are not many options when you do. You would get better odds on tossing a coin than getting the same sort of job you had before,” she told The Times.

The debate on the balanced life has been about high-flying executives who do nothing but work. Doing nothing but parenting is just as bad, she says.

“If you told me that you were spending all of your time at work I would say to you, your life is woefully imbalanced. It’s the same thing if you’re spending all of your time parenting — your life is woefully imbalanced. You will be bored and unfulfilled.”

Licia Ronzulli, an Italian MEP, takes her daughter to the European parliament

Working one way or another, even one or two days a week, when children are small will make life a lot easier and happier later on. “I am saying keep your foot in the door or there will not be any doors open.”

Ettus, 44 and a mother of three, said it was not her intention to anger or hurt the feelings of those who choose to stay at home. “I have been mistakenly accused of criticising parents when all I want to do is give women choices. We all know amazing parents who stay at home and terrible parents who stay at home, likewise great and crappy parents who work. There is no correlation between the quality of parenting and relationship with the child and whether you stay at home or work.”

The best parents are the happiest people and they have balanced lives, with hobbies and a social life, a job and time to spend at home. She reckons that there are seven slices in the pie of life including friends, hobbies, and health as well as a job, children and a relationship.

Her advice on how to pack all that in is get up an hour earlier to crack on with emails, exercise or chores and to exploit the “golden triangle” of the route between home, school drop-off and work to fit in shopping, hair appointments and the dentist.

About one in ten women in Britain is a full-time mother, although up to a third stop work when their children are very young. The statistics show they pay a high price when they seek to return. The Institute for Fiscal Studies found the pay gap between men and women widens to about 33 per cent 12 years after the birth of the first child.

Time out — or overtime?

Rachida Dati: French minister was back in work five days after giving birth

Take a break
Annabel Karmel, 59, gave up life as a professional harpist after the death of her first child. She re-entered work as a children’s cookery writer and has written more than a dozen books.

Lily Allen, 31, quit as a singer for four years to be with her young children. When she went back on tour she dubbed her return “the mumback”.

Margaret Rayman had a 17-year career break as a research scientist before going back into the lab and made breakthroughs on dementia and nutrition.

Keep going 
Rachida Dati 50, went back to work as France’s justice minister five days after giving birth.

Helen Wright was back at her desk as head of St Mary’s Calne, a girls’ boarding school, seven hours after giving birth.

Marissa Mayer, 41, The Yahoo chief executive took two weeks’ maternity leave after the birth of her first child and a month after having twins.