Although sounds are muffled by the surrounding amniotic fluid, your baby can hear even in the womb -- and she'll probably come to know your voice quite well. Her hearing gets sharper over the first year of life, and she also learns to recognize where sounds are coming from. For the first three months, your baby will only turn toward a sound that comes from in front of her, but by 6 to 12 months she should also be able to track sounds coming from behind her or from the other side of the room.
Your infant prefers high-frequency tones like the female voice, probably because she can hear them better. Maybe that's why it's natural for adults to adopt a high-pitched singsong voice (also known as "motherese") when talking to babies. By 4 to 6 months your baby should start to repeat recognizable sounds and babble.
Some newborn hearing impairment is genetic. But a baby can be born with hearing loss even if there's no obvious family history. For example, both parents may carry a recessive gene for deafness, causing the child to inherit the trait. Other causes of congenital hearing loss are low birth weight (a baby born weighing under 3.3 pounds) and a mother's infection with certain viruses, such as rubella or cytomegalovirus (CMV) during pregnancy.
After birth, chronic and untreated ear infections can cause damage to a baby's ears, ranging from rupturing of the eardrum to, in rare cases, permanent hearing loss. The temporary hearing loss that often comes with an ear infection, due to fluid blocking the middle ear, can also be problematic if your baby is getting one infection after another. The recurrent hearing impairment can interfere with a baby's language development. After your baby is treated with antibiotics, make sure to schedule a follow-up visit so the doctor can check that your baby's ears are indeed clear.
Hearing impairment is one of the most common birth defects. Every year in the United States, 12,000 children are born with a hearing impairment, and 4,000 of them are deaf. The good news is that with early intervention, these children can achieve normal language development. Many people don't know that there are hearing aids and therapy for infants only weeks old; cochlear implants are possible once a child is 1. A University of Colorado study found that out of a group of 150 children with a hearing loss, children who were identified and fitted with hearing aids by 6 months of age had normal language development at age 3. In contrast, the language skills of kids whose hearing problem wasn't detected until after 6 months of age tested below normal at age 3.
You might assume that your doctor is evaluating your baby's hearing at well-baby visits. But while he's checking for signs of fluid and infection, he's not formally testing your child's hearing. Fortunately, thanks to recent technological advances and a greater awareness of the importance of early detection, hearing-screening programs for newborns are starting up in more and more hospitals across the country, making early diagnosis of any problem almost routine. One study showed that when babies were screened as newborns, hearing loss was identified at about 2 months of age instead of the current average, 2.5 years. The screenings involve two simple, painless tests that can be done while the child is sleeping.
Ask your pediatrician if your child's hearing was screened at birth; if it wasn't, find out about scheduling a test. Early assessment is especially important if any member of your family has a hearing problem or if your baby was premature or very ill as a newborn.
To find out if your state performs newborn hearing-screenings, visit www.hearinghealth.net.
Here's an age-by-age guide of signs to watch out for:
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