Bottles

Small, 4 fl oz (118 mL) bottles are a good size to use when your baby first comes home from the hospital. As your baby starts to take more formula during a feeding, you will likely want to have bigger 8 fl oz (237 mL) bottles on hand.

Bottles are made of glass or plastic.

• Glass bottles can be cleaned by boiling them; plastic cannot.
• Wide-mouth bottles are easier to clean.
• Some plastic bottles are made for single-use plastic liners. Some people find these bottles clean, easy to use, and convenient.

Some people are concerned about bisphenol A (BPA), a chemical in some plastic (polycarbonate) bottles. Research hasn't shown that small amounts of BPA harm humans, but researchers are doing more studies. If you don't want to use this type of baby bottle (which may be marked with the number 7 or the letters "PC" near the recycle symbol), you can use glass or BPA-free plastic bottles.

Nipples

Nipples have been designed to imitate a mother's nipple. The human nipple is short and flexible, which makes it easy for a baby to grasp and suckle. However, some babies have difficulty with some bottle nipples that are too short.

General guidelines for buying bottle nipples:

• Buy more nipples than bottles. With repeated use, nipples tend to crack and leak.
• Choose nipples that are made of silicone or rubber. Silicone nipples cost more but are more flexible than rubber nipples. Silicone nipples are not damaged by heat when they are boiled.
• The nipple hole should allow liquid to drip slowly. To test the nipple drip, hold the bottle upside down without shaking it. Milk should drip about 1 drop per second.

Nipple shapes include:

• Standard nipples, which have a long rounded tip and are easy for the baby to use.
• Nubbin nipples, which have short, flattened tips and are usually used with bottles that have disposable plastic liners. The nubbin nipple is sometimes more difficult for the baby to grasp, especially if the baby is also breast-fed.
• Orthodontic-type nipples, which have a long, irregular shape that is designed to mimic the shape of the mother's nipple when it is in the baby's mouth. Babies need to suck on the wide flat part of this nipple, not the shorter tip.
• Tricut-type nipples, which are longer than the standard nipple and most closely imitate the mother's nipple. Their increased length releases milk farther back in the baby's mouth, making it easier for the baby to swallow.

You may need to experiment with a few different types of nipples until you find one that seems most natural for your baby.