Hi,

I wonder if the health professional who advised topping up the baby with formula spoke to your friend about ways she could increase her milk supply? It is important that babies gain weight. We usually expect a baby to lose up to 10% of their birthweight and then to regain it by 2 weeks or so. If this has not happened, then it is important that the causes are identified, and then a few simple measures will mean baby gets more milk, mother produces more milk and then breastfeeding goes on really well.
What the WHO growth charts will tell you is that it is normal for babies to grow quickly in the first 3 mnths - in fact, formula fed babies generally lag a bit behind the normal growthrate (breastfeeding is the norm) Then, at around 3 months, a baby's weight will plateau.
Suggest your friend ring the Australian Breastfeeding Association helpline. She will be surprised how easy it is to overcome these early difficulties

Warm Regards
Barb