Do you often come to blows with your mother or partner's mother over how best to feed your baby? You're not alone. Here's Dr Sears' advice

Q I just learned that when my mother babysits my four-month-old, she gives her a bottle of water after she is finished with her regular bottle. I'm upset that she's taken it upon herself to do this without consulting me first, and I'm also concerned because I've heard that water isn't necessary or even good for babies. How can I explain this to my mum without offending her. Does Granny know best?

A Throughout my career as a paediatrician, I have learned to greatly respect grandmothers. They usually make the best babysitters, because that blood relationship gives them an advantage in all aspects of caregiving. My wife and I have eight grandchildren ourselves, and it is such a privilege for us to take care of them. While you are very fortunate to have your child's grandmother as a babysitter, you are still your baby's mother, and you are the one to call the shots on what you believe is best for her. Here's how to gently guide your mum into your way of thinking:

Blame it on the doctor

A tip I give my patients when they are divided with family members on a sensitive health issue, and want to take the heat off of themselves, is to simply say that "the doctor said so." Many people of your mother's generation grew up in an era when it was the norm to follow medical advice without question, so it's likely she'll respect the doctor's final word.

Choose your battles wisely

Differences in childcare beliefs frequently cause friction among family members, and the last thing you want to do is alienate your mother. I suggest you focus on the bigger issues, and ignore the smaller ones. In my opinion, your mum giving your baby a bottle of water after a feeding is a small issue — as long as it doesn't lessen the amount of necessary formula or expressed breast milk that your baby takes and she's gaining weight properly, then you don't need to worry about it.

A formula-fed baby needs approximately 2- to-2.5 ounces of formula per pound of weight each day.

You might be reassured to know that if your baby is on formula, a bit of extra water is probably good for her. Since formula can be more concentrated than breast milk, we often advise that formula-fed babies get an extra four to eight ounces of water daily to help the developing kidneys function and properly process the formula. That said, if your baby is drinking expressed breast milk from her bottle, extra water is not necessary.

You can also compromise by asking your mum to give her just an ounce or so of water after her regular bottle. Finally, trust your baby's own instincts — she's not going to eat more than she needs to. If you look into it, you'll probably realise that she's taking only a small amount of water after the bottle.

Focus on the social interaction

Occasionally, watch your mother when she gives your baby a bottle. It's likely to be a high-touch social interaction between the two of them, not just a routine delivery of milk. The extra cuddle time that your baby gets from her grandma during feedings is probably worth overlooking any feeding liberties your mum may take.