No milk formula is perfect - breastfeeding is best.
If you are unable to breastfeed, then a formula is a reasonable substitute, said Dr Nancy Tan, a paediatrician from SBCC Baby and Child Clinic at Gleneagles Medical Centre.
There is no way to predict if a particular formula is best for your baby as every child has his own unique digestive system and nutritional needs.
Premature or low birth weight babies may need formulas with a higher protein or caloric content to help them grow and gain weight.
Those with severe cow's milk allergy may require soya, extensively hydrolysed or amino acid formulas.
Babies with reflux problems may need anti-reflux formulas with thickeners to help them keep the milk down better. Babies who suffer from lactose intolerance may need a lactose-free formula.
And those with a strong family history of allergies and eczema may do better on a hypoallergenic formula.
There is also no ideal time to switch from breast to milk formula.
Breastfeeding can continue as long as you are still lactating and meeting your baby's demands, according to Dr Wong Boh Boi, assistant clinical director and senior parent craft/lactation con- sul tant at Thomson Medical Centre.
You can consider switching to formula when you are put on medication or when your child has medical conditions like galactosaemia, a genetic disorder which affects the body's ability to process a simple sugar called galactose.
Other practical reasons include returning to work or when you are experiencing fatigue.
When in doubt, check with a lactation consultant or your baby's paediatrician.
And all infant formulas must meet basic nutrient standards to promote optimal growth and development.
Less expensive ones are just as good as pricey brands as they meet the nutritional requirements for infants, said Dr Wendy Sinnathamby, a paediatrician at Raffles Children Centre.
Although manufacturers vary their formula recipes, all approved formulas will contain the minimum and no more than the maximum recommended amount of nutrients babies require.
It is also not uncommon for infants to get constipated when they switch to a follow-on formula.
This is because whey, usually the main form of protein in newborn formula, is replaced by casein in follow-on formula, said Dr Sinnathamby. Casein moves through the gut more slowly than whey.
This allows more water to be re-absorbed within the gut and makes the stools harder. Follow-on formulas also have a higher iron content, which can also contribute to constipation, she added.
Stick to one brand and change only if your baby has problems with it.
Babies who are drinking soya or hypoallergenic formula generally do so for a period of either six or nine months to a year, said Dr Eugene Han, a paediatrician from Thomson Paediatric Centre.
After that, the doctor may recommend a skin prick test to determine if the child still has cow's milk protein allergy.
Most babies still rely on milk for most of their intake of calcium, which is particularly important for building strong bones, teeth and muscles.
But you can also offer plain whole-milk yogurt and pasteurised cheese after your child turns six months old, said Dr Han.
Do not opt for low-fat versions, though, as they lack the fat your baby needs for healthy growth.
•This article first appeared in Young Parents magazine. Young Parents, published by SPH Magazines, is available in both digital and print formats. Go to www.youngparents.com.sg to subscribe and for more parenting stories.