Fathers invest more and harder hours in the workplace when their first child is born and then longer still on the arrival of their second.

The jury is out on whether this is the hunter-gatherer instinct kicking in or a way of avoiding the demands of a new baby in the home.

Fathers need to resist this instinct and spend more time at home, not less, advises the Parent Talk Guide to the First Six Weeks (Hodder and Stoughton, £5.99) . Fathers should not work late unless it is absolutely necessary and should keep work-related socialising to an absolute minimum, advises author Tim Mungeam, chief executive of Parent Talk, a British parenting organisation.

"Many successful businessmen and captains of industry have reached positions of influence without compromising their role as fathers," he writes.

Fathers need to be aware that having a baby can break a relationship, rather than bringing parents closer. The new mother is recovering from the birth and is wrapped up in her baby's needs.

The father is trying to look after the mother, while also carrying out all his usual roles. He may feel left out, especially when sleepless nights make the couple so tired that when the baby falls asleep, they do too.

Mother and baby may end up sleeping in one bed (especially if mother is breast-feeding) and father in another bed. That can turn into a permanent situation.

Contented couples usually end up with better-adjusted children and "easier" babies, so new parents need to find time to talk and to listen to each other while the baby is asleep. That means turning off the TV instead of lying on the sofa with a glazed expression and channel-surfing, suggests Mungeam.

Yes, Dad, that means you.