Since the AAP (American Academy of Pediatrics) started recommending that mothers continue nursing for at least the first year of a baby's life, more and more mothers find that they become pregnant while they are nursing an older baby. Many babies will wean themselves during the pregnancy, especially during the later months, because the milk supply decreases and the taste changes as the breasts start producing colostrum. However, some babies don't seem to care whether they are getting a lot of milk when they nurse. That's where the emotional component of breastfeeding becomes a big factor. Babies vary in their need for oral satisfaction, physical contact, closeness to mother, and willingness to have those needs met in ways other than nursing. 

Some toddlers continue to find breastfeeding very important all the way through the pregnancy and after the birth of the new baby as well. Nursing siblings who are not twins is called "tandem nursing". In our culture, this concept is unusual, although other in many other cultures it is a common practice. 

It is not unusual to have mixed feelings about tandem nursing. Negative feelings are common, due to physical discomfort and fatigue, as well as feeling "touched out" after nursing for so many months. For the mother who finds herself resenting the older baby's demands, and has difficulty focusing enough attention on the new baby, weaning may be the best choice. She should try to wean gradually, nursing the new baby when the toddler is occupied with other things, and substituting special activities and snacks for nursings. Dads can be a big help with this process. 

When they do choose to tandem nurse, many mothers find that a unique closeness develops between their nursing siblings. Sharing at the breast can reduce the jealously and sibling rivalry that often accompanies the arrival of a new baby. 

Because the older child is receiving nourishment from foods other than breastmilk, the newborn should be allowed to nurse first, ensuring that he gets lots of colostrum. Nursing a toddler can help relieve engorgement. Because the toddler will nurse more vigorously than the infant, the mother may find that she produces an oversupply of milk. If this occurs, and the newborn chokes when attempting to nurse, she may want to let the toddler nurse briefly before putting the new baby on the breast. Within a short period of time, the milk supply will adjust to the needs of the two siblings, just as it would if the mother were nursing twins or triplets. The two nurslings can be fed at the same time, or separately - whatever works best for the mother. It is a good idea to switch breasts rather than restricting each child to one side, because nursing on both breasts promotes development of eye-hand coordination. 

There are no special concerns about hygiene. The nipple secretes an enzyme that reduces bacterial counts, and breastfed babies are born with immunities to most germs found in their home environment. Most germs involved in common illnesses are contagious for days before symptoms appear, so tandem nursers have been exposed by the time you know one of them is ill. If you are dealing with a serious illness, one that is very contagious, or thrush, you may want to limit each child to one breast temporarily. 

Sometimes a toddler who was weaned before the new baby's arrival will decide that he wants to nurse again. Often a discussion of how he used to nurse, but now he's a "big boy" and can eat grown up food, will suffice. If he is insistent about it, it is probably best to let him try. Most of the time toddlers who have weaned have forgotten how to nurse, and will lose interest quickly. Allowing him to nurse until he feels more secure about his new position in the family can be a good idea. Another possibility is offering him a taste of breastmilk in a cup to let him see if he likes it. Most toddlers who have weaned are used to drinking cold liquids, and may not like the warm milk. However, some older babies love the taste and say that it tastes like "melted ice cream"! 

Tandem nursing is not for everyone. If it is not working out well, mothers should wean the older child without feeling guilty about it. It is important to give the older baby lots of extra cuddling and attention so that he knows that although he is losing the comfort and security of the breast, he is not losing his mother's love.