My friends Dave and Patricia have two kids, Xavier and Declan. They're what are technically known as "beautiful" boys: huge eyes, long lashes, button noses, and mischievous grins. Both are sociable and cuddly, but while six-year-old Xavier speaks like an adult, two-year-old Declan doesn't talk yet.

In fact, until a month ago Declan had not even begun to babble or imitate the outside world. He laughed, cried, and screamed with gusto, but the critical aspect of language development was missing. Fortunately, Patricia is trained to help kids with special needs, and she and Dave have been able to get Declan the help that he needed. Chances are if your child is developmentally delayed, you and your pediatrician will pick up on milestones that just aren't being met.

Checking Developmental Milestones The first step in recognizing possible delays in development is to compare your child's abilities with the expectations for the average child at his or her age. The following milestones for social interaction and language skills come from First Signs, Inc., a national non-profit organization dedicated to educating parents and pediatric professionals about the early warning signs of autism and other developmental disorders.   Four months: Follows and reacts to bright colors, movement, and objects. Turns toward sounds. Shows interest in watching faces. Returns smiles. Seven to eight months: Sits unsupported. Imitates sounds. Crawls. Claps, points, waves. Bangs two objects together. Understands "no" from your tone of voice. 12 months: Uses a few gestures to get needs met and likes using hands to communicate, share, or point. Will turn to a person speaking or when his name is called. Plays peek-a-boo or other social games. Makes rudimentary mono-syllabic sounds such as "ma," "ba," "da," and "ga." 15 months: Exchanges smiles, vocalizations, and gestures with you. Uses pointing and other motions to draw attention to something, uses voice to get needs met or garner attention. May be able to speak and understand three or four words, such as "momma," "poppa," "bottle," or "bye-bye." 18 months: Uses lots of gestures as well as words to get needs met, like pointing or taking you by the hand and directing you to something. Uses at least four different consonants in babbling or words, shows that he knows the names of familiar people or body parts by pointing to or looking at them when named, and plays simple pretend games (like feeding a doll). 24 months: Engages in complex pretend play (such as feeding a doll then putting it to sleep). Uses and understands at least 50 words and can string words together. Enjoys being with children of the same age and is interested in playing with them and/or sharing toys. Looks for a familiar object out of sight when asked about its whereabouts. 36 months: Enjoys pretend play with different characters and with a story line, enjoys playing with other children, uses thoughts/actions together with speech to communicate and play. Will answer simple "who," "what," and "where" questions easily and talks about things in the past and the future.

It's important for parents to remember that a chart of milestones can't take the place of a screening test performed by a specialist. Rather, the milestones chart will only help parents know whether they should raise their concerns—and also how they can explain those concerns to the doctor.

For parents who want more specific resources before consulting with a doctor, there are screening tools available for order online. The medical testing company Forepath (www.forepath.org) offers its PEDS Child Development Screening Test over the Internet for a small fee. The online test also includes the M-CHAT (Modified Checklist for Autism in Toddlers) for parents whose children are over 18 months but younger than five.

Talking to Your Child's Doctor Once you've identified areas of suspected delay in your child's development, make an appointment with your general practitioner or pediatrician. While these doctors rarely get involved in the diagnosis and treatment of developmental disorders, it is generally necessary to get a referral from them for a consultation with the appropriate specialists.

To confirm her suspicion that Declan was undergoing a developmental delay in language, Patricia checked a range of milestone charts. She saw that Declan's problem-solving, cognitive, and motor skills were all normal; however, he was several months overdue for milestones in receptive language (understanding what is spoken to him) as well as expressive language (speaking to others). She took him to the family practitioner, who referred her to a speech pathologist and an audiologist.

Visiting the Specialists As in Declan's case, the referral from a general practitioner or pediatrician will usually include more than one specialist. The audiologist found that Declan's hearing was at the lowest level of the normal range; due to repeated ear infections, he has fluid in his middle ear that will require tubes to drain. Hearing plays a significant role in children's development of language, especially in children up to three years, who fall into what the National Institute on Deafness and Other Communicative Disorders has termed the critical period for language development. The expectation is that Declan's language abilities will jump once his hearing improves; if they don't, however, there may be other problems preventing his development and further tests by other specialists (such as psychologists and neurologists) would be undertaken.

After the audiologist's testing, the speech pathologist did a developmental assessment on Declan and determined that his receptive language development was six-months delayed and his expressive speech was twelve-months delayed. The specialist recommended speech therapy every two weeks. After two months of therapy, Declan's vocabulary increased from two to 25 words.

Declan's story is turning out well so far, thanks to early and rapid intervention. His mother knew exactly what kind of assessments to expect and which treatments would be recommended depending on the results. However, for concerned parents who feel overwhelmed by a lack of understanding about their child's problems, specialist visits can be intimidating. The National Center for Infants, Toddlers, and Families has a website of information about young children's development, which includes a comprehensive guide for understanding and working with developmental assessments.

Managing Problems While some developmental delays can be overcome through treatment, as in Declan's case, often the assessment of these delays can lead to the diagnosis of one of a range of Pervasive Developmental Disorders (PDDs), the most commonly known of which is autism. PDDs are often called Autism Spectrum Disorders because they are classified by the severity of the symptoms present. For example, autistic children have significant deficits in social interaction and communication and they tend to engage in repetitive behaviors such as rocking and stroking or tapping themselves. By comparison, children with Asperger's can use language much more effectively, although one symptom of Asperger's is a fixation on an object to the extent that the person speaks to others mainly about that object, regardless of social situation.

According to the National Institute of Mental Health, symptoms of PDDs can be detected in children as early as from birth to one year. In terms of assessment and treatment, doctors will generally refer to a child psychologist or psychiatrist if a PDD is suspected. Treatment can help alleviate symptoms of PDDs (for the child as well as the child's family), but as the term "pervasive" suggests, these disorders cannot be outgrown or cured.

Finally, a word on recognizing, testing, and treating sensory integration problems. The concept behind these problems has been around since the late 1970s, when occupational therapist A. Jane Ayres presented a theory unifying some children's highly exaggerated sensory responses—of touch, taste, sight, smell, and sound—under the term Sensory Integration Dysfunction (SID). For example: A child with auditory defensiveness may cover his ears and throw a tantrum if his kindergarten class sings a song together. A child with tactile defensiveness may violently resist wearing shoes or may be agitated by the inside tags in her clothing. More detailed descriptions of children with SID can be found on the website for Carol Kranowitz's benchmark book on SID, The Out-of-Sync Child.

Perhaps because SID has been largely studied and treated by occupational therapists rather than psychologists, and because its definitions are still being clarified, SID does not appear in the DSM-IV, the official manual of mental disorders. Diagnosis and treatment of SID, then, must usually be undertaken by an occupational therapist certified to administer the Sensory Integration and Praxis Tests (SIPT).

While not categorized as an Autism Spectrum Disorder, SID presents parents with the similar challenge of early detection and intervention—not because SID can be cured, but so that the child and his family know how best to minimize and adjust to the symptoms.

Related Content: Ask the Experts: Is Back Arching a Sign of Developmental Delay? Is My Child Developing Properly?

About the Author Kevin Klein and his wife, Leah, have begun to use their biological clocks as stopwatches. They have toddler daughter, Alexis, a baby son named Tyler, and they plan (for now) on having one or two more kids just as quickly. Kevin teaches and writes; Leah maintains a small private mental health practice. For now.