I don't believe there is any compelling reason to avoid pacifier use for infants, particularly after the first 4 weeks (although earlier might be okay, too; see below). Ultimately, the decision may be influenced by your child's preference. My son had absolutely no interest in pacifiers by the time he was about 2 months old.
In truth, there actually is some compelling evidence in favor of pacifier use (if your child will use them): there is some evidence that pacifier use in the first year can reduce the likelihood of SIDS.
The potential negatives, particularly in the first year or two, are relatively few.
One of the primary concerns for artificial nipples/pacifiers is related to breastfeeding. Nipple confusion is the term commonly used to describe a child developing a preference for a specific type of nipple that conflicts with their normal feeding method (usually the undesired preference is for an artificial nipple, although a preference for breastfeeding in a child who, for whatever reason, will not typically be breastfed, could also fall into this category).
There is some debate over whether pacifier use can interfere with breastfeeding. Marie's very good answer to that question references some research that found no correlation between pacifier use and reductions in breastfeeding. However, she raises the issue of infants preferring the easiest route, and if breastfeeding is difficult for the child, it seems possible that use of a pacifier could complicate the process of learning to breastfeed further.
Another concern is the potential of dental problems. However, according to the Mayo Clinic this is not an issue during the first few years of a baby's life.
The Mayo Clinic also provides a nice Pro/Con list for pacifier use:
Pro
- A pacifier might soothe a fussy baby. Some babies are happiest when
they're sucking on something.
- A pacifier offers temporary distraction.
A pacifier might come in handy during shots, blood tests or other
procedures.
- A pacifier might help your baby fall asleep. If your baby
has trouble settling down, a pacifier might do the trick.
- A pacifier
might ease discomfort during flights. Babies can't intentionally "pop"
their ears by swallowing or yawning to relieve ear pain caused by air
pressure changes. Sucking on a pacifier might help.
- Pacifiers might help reduce the risk of sudden infant death syndrome (SIDS).
Researchers have found an association between pacifier use during
sleep and a reduced risk of SIDS.
- Pacifiers are disposable. When it's
time to stop using pacifiers, you can throw them away. If your child
prefers to suck on his or her thumb or fingers, it might be more
difficult to break the habit.
Con
- Early pacifier use might interfere with breast-feeding. Sucking on a breast is different from sucking on a pacifier or bottle, and some babies are sensitive to those differences. Research suggests that early use of artificial nipples is associated with decreased exclusive breast-feeding and duration of breast-feeding — although it's not clear if artificial nipples cause breast-feeding problems or serve as a solution to an existing problem.
- Your baby might become dependent on the pacifier. If your baby uses a pacifier to sleep, you might face frequent middle-of-the-night crying spells when the pacifier falls out of your baby's mouth.
- Pacifier use might increase the risk of middle ear infections. However, rates of middle ear infections are generally lowest from birth to age 6 months — when the risk of SIDS is the highest and your baby might be most interested in a pacifier.
- Prolonged pacifier use might lead to dental problems. Normal pacifier use during the first few years of life doesn't cause long-term dental problems. However, prolonged pacifier use might cause a child's top front teeth to slant outward or not come in properly.