Most moms understand that not nursing their babies often enough or supplementing with anything too frequently can compromise milk supply. But there are several "hidden" possibilities as well that should be considered:
The use of certain medications. All of the following have been associated with lowering milk supply: antihistamines and some decongestants, some weight loss medications or appetite suppressants, very high doses of vitamin B-6, diuretics, etc. There are other medications - both prescription and over-the-counter, that, although they may pose no significant risk to your baby, may adversely affect your milk supply. For this reason, it's always a good idea to check with a board certified lactation consultant (IBCLC) when beginning a drug you have never taken before.
Hormonal birth control. It's a well-established fact that birth control options containing the synthetic hormone, estrogen, can result in a diminished milk supply, sometimes quite rapidly. While most women can use the progesterone-only contraceptives, caution should be used when choosing this birth control option as well. No hormonal birth control should be started before the 6th-8th week postpartum. This allows the body plenty of time to fully establish a milk supply before any hormones are introduced that could compromise this process. Also, the baby's liver is too immature before this time to adequately metabolize the hormones in the contraceptive. After the 6th-8th week, if a hormonal birth control is desired, begin with a progesterone pill (mini-pill). This way you can quickly stop taking it if you notice a drop in milk supply. Most lactation experts advise avoiding the Depo-Provera injection while breastfeeding since it lasts three months and thus cannot be stopped if a drop in milk supply is noted. Estrogen-containing contraceptives should be avoided till at least after the 6th month and once the baby is well-established on solid foods.
Low thyroid (hypothyroidism). Some women can develop this condition for the first time during pregnancy and lactation. A test to check the thyroid function is always a good idea when a low supply does not respond to the usual methods for increasing it. Other symptoms of low thyroid include excessive hair loss, dry skin, increased sensitivity to cold, loss of appetite, extreme fatigue, depression, and a swelling in the neck area. If a low thyroid is diagnosed, the medication to increase its activity is compatible with breastfeeding.
Anemia. Just as with a dysfunctional thyroid, anemia should be ruled out when a low supply does not respond to measures to increase it or if another cause cannot be found. Mothers with anemia are also at greater risk for plugged ducts and breast infections.
Smoking. Mothers who smoke more than 20 cigarettes a day often experience a lower milk supply. Their babies also tend to gain weight more slowly than the babies of mothers who smoke fewer cigarettes each day or those who do not smoke at all. See more on smoking and breastfeeding here.
Rapid weight loss. When lactating it's recommended that you not lose weight more rapidly than one pound a week or about 4 pounds a month. Losing weight more quickly than this can reduce the quantity of your milk as well as pose certain risks to your baby. Exercise wisely and try to take in at least 1800 calories a day while breastfeeding. Avoid weight loss medications, drinks, or other fads.
A history of hormonal problems. The mother who has difficulty conceiving or carrying a baby to term may experience problems with establishing a full milk supply; although this does not appear true for all moms who fall into this category.
A previous breast surgery or injury. Women who have previously had breast augmentation or breast reduction surgeries are at greater risk of never fully establishing a milk supply. This is more likely if the milk ducts were cut during the surgery and have not grown back, or "recanalized". Surgeries in which the nipple is removed and relocated tend to result in more of the milk ducts and nerves being severed. When deciding upon either of these surgeries, plan to fully discuss with your doctor preserving the possibility of future breastfeeding. Get a second opinion if your doctor says that the surgery will in no way affect breastfeeding. This is most always not true! While many mothers who have had these surgeries do go on to at least partially breastfeed, if a woman strongly wants to nurse her future babies, the decision to have either of these surgeries should not be entered into lightly.
Women who have experienced some type of breast injury (burning, trauma, through radiation therapy, congenital defect, etc.) are also at greater risk for many of the same reasons stated above. They, like those women who have had elective surgeries, should still be encouraged to breastfeed. Most are able to at least partially provide milk for their babies.
A retained placenta. If the placenta was not able to be removed intact or if postpartum bleeding occurs for more than 6 weeks, this is a possible hindrance to a healthy milk supply. Excessive postpartum bleeding (hemorrhage) has also been related to low milk supply.
Insufficient glandular development. Very rarely, a mother's breasts will not be able to produce an adequate milk supply for her baby. Simply put, the milk ducts and glands have not developed well enough to properly work. Mothers with this condition typically report that their breasts did not change in size or shape during pregnancy. There may also be a marked difference in the size or shape of the breasts. There is no note of the "milk coming in" during the early days postpartum and the breasts never feel full or engorged. These mothers should still be encouraged to breastfeed. While their babies will need to be supplemented in order to receive enough milk, the amount of mother's milk received will still be invaluable.
Overuse of the pacifier. Babies all need to suck and it is this desire that often ensures that the baby is at mother's breast frequently enough to maintain her supply. Avoid using a pacifier if possible. Along with compromising milk supply, pacifiers have also been linked to greater incidence of ear infections and thrush and premature weaning. If you choose to use one, use it only after a feeding and watch your baby for signs that he is loving his pacifier too much. Limiting pacifier use is one effective way of increasing milk supply if needed.
Early introduction of solids. When babies are introduced to anything other than mother's milk before the 6th month or later, there is an increased risk that the mother's supply will drop. There are other risks as well. Solids displace the breastmilk in the baby's diet. He in turn nurses less frequently; thus reducing the amount of stimulation his mother receives. Delay introducing any solids (cereal included) before the 6th month and breastfeed BEFORE offering the solids until closer to the end of your baby's first year. This will ensure that he nurses frequently and that the bulk of his calories still come from your milk as they should for most of the first year. Continue feeding on baby's cue even after solids have been introduced. Limit water and juice intake to mealtime and from a cup. Limit overall juice intake to 3-4 ounces.
Encouraging the baby to sleep through the night. Often babies are encouraged or "trained" to sleep through the night too early. This can often compromise the mother's milk supply. If your baby decides to sleep through the night on his own and your milk supply is adequate then let him sleep. But avoid the temptation to sleep "train", especially if your supply is of concern. Night feedings are the most beneficial for increasing milk supply.
Faulty latch or suck problem in the baby. Both of these can adversely affect milk supply since the milk will not be removed from the breast well. Inadequate milk removal tells the body to reduce the supply over time. If either of these are a concern, an assessment by a board-certified lactation consultant is in order.
Limiting the baby's time at the breast or failing to offer both breasts at each feeding. Allow your baby to completely finish one side before you offer the other by waiting until he falls asleep, pulls off himself, or stops actively sucking and swallowing. Always offer both breasts at each feeding. Your baby may not always want or need the second side, but it should always be offered. Start each feeding on the side the baby finished with (or took the shortest period of time at the last feeding) or the breast he did not take at all. Nursing in this way will ensure that both breasts receive adequate stimulation.
Use of a nipple shield. Using a nipple shield decreases the amount of stimulation to the breast and the amount of milk transferred. Both can adversely affect supply. If a nipple shield is required, choose a silicone one that will allow for more stimulation and use only under the direction of a board certified lactation consultant.
Pregnancy. Most mothers notice a drop in milk supply about halfway through their pregnancy. This is due to changing hormone levels.
Returning to work, especially before the 6th-8th week. Delay your return to work as long as possible to give your body time to adequately establish your milk supply. Once back at work, arrange to pump for missed feedings regularly, using an effective pump. Both not pumping regularly and using an ineffective pump can cause your supply to quickly decrease. When home with baby make it a rule to only nurse. No bottles during the evenings and on weekends. Even allowing your baby to comfort nurse at your breast - instead of using a pacifier - will help maintain your milk supply with more ease.
Additionally, both excessive caffeine and alcohol use have been attributed to letdown difficulties. While not directly related to supply, a delayed or inhibited letdown can lead to supply problems. Try to limit your caffeine consumption to less than that contained in 4-5 cups of coffee a day. Limit alcohol use to one drink or less a day on average. Extreme stress and fatigue have also been noted as hindrances to a fully functioning letdown response.