As Serena Williams is finding out, breastfeeding can be a minefield. The tennis champion, who became a mother for the first time in September, asked for advice from her Twitter followers yesterday about just how long she should keep feeding her son, Alexis Jr.

"Fellow moms," she wrote, "How long did you breastfeed? Is it weird that I get emotional when I even just think about when it's time to stop."

On almost all matters to do with breastfeeding, here are hundreds of opinions out there, and every one seems to be different. When to stop? Should you do it at all? In public? Is formula better? What if you're struggling?

It means that, often, many mums have no idea what's true and what's not, when it comes to feeding their babies. They can feel pressured and even guilty.

Mumsnet poll of 1,030 mums to mark World Breastfeeding Week, this week, found that three-quarters said they believed that there was "too much emphasis on telling women why they should breastfeed, and not enough on supporting them to breastfeed".