Many times moms use other criteria to evaluate the adequacy of supply. Some of these other measures may evaluate other characteristics of milk, such as quality, but these are NOT good criteria for measuring milk supply:
If your pediatrician notices an inability of your baby to regain her birth weight in the first few weeks, he may recommend supplementing your breastfed baby's diet with formula to prevent failure to thrive. Failure to thrive is a treatable condition, classified as an inability to take in, retain, or utilize the calories needed to gain weight and grow as expected.
In the absence of failure to thrive concerns, supplementing with formula in the first month can put you and your baby at serious risk of not developing a complete breastfeeding relationship, which can induce failure to thrive in later months. Bottle nursing requires less effort from your baby to draw milk out (whether formula or breast milk), so it is best to avoid bottles for the first 4- 6 weeks-until baby has developed a good, strong suck at the breast that can adequately draw the fat-rich hindmilk, which provides calories for weight gain and satiety.
When You Do Have Low Milk Supply
If you have determined (with the help of your healthcare provider and lactation consultant) that you do have a low milk supply (characterized by slow weight gain and not enough soppy wet and dirty diapers), the most common cause is usually inefficient calorie and fluid intake for mom.
In the first days and weeks of breastfeeding a new baby, your focus is oftentimes on feeding your baby, recovering from delivery, catching sleep when possible, and adjusting to life with an expanded family. In the midst of all this transition, you may nibble on food throughout the day but not really eat the way you should. You may even feel that you are eating, but when you take a closer look, you may notice that your caloric intake is not near your body's increased needs. Breastfeeding is very energy demanding, so without adequate calories and water, your body cannot produce the milk that your baby needs-regardless of how hard baby is trying or how frequently she is at the breast.