At a routine checkup for my 6-month-old, Molly, I went from calm observer to tearful bundle of nerves in 30 seconds flat. The doctor told me that Molly's hips might be dislocated and that she needed an x ray. During the wait for the results, I drove myself (and my husband, mother, and sisters) nearly crazy, projecting scenarios of Molly in a wheelchair, or on crutches, or in pain. When it turned out her hips were just loose naturally, needless to say I was relieved. But I never took a routine exam for granted again.

Well-baby checkups are usually happy occasions -- you find out that your little one is thriving, that she's on-target (or ahead of the curve!) with her milestones, that she's just the cutest thing the office nurse has ever seen. But once in a while, the pediatrician will pick up on something that's not quite right. That can be freaky -- but the fact is, even the scariest-sounding symptoms rarely turn out to mean that something's seriously wrong. Here are six of the most common ones and fear-calming information about each.

Dislocated hips

It's good my doctor was so observant about Molly's hips, even if it did scare the bejesus out of me. About one in 1,000 babies has dislocated hips, or developmental dysplasia, says David Roye, Jr., M.D., chief of pediatric orthopedic surgery at the Morgan Stanley Children's Hospital of New York Presbyterian. "This can be anything from a joint that's dislocated at birth to movement that's so subtle, it won't be noticed until age fifty, when the person starts having hip pain." Risk factors include being a firstborn, female, breech, and having a family history of the disorder.

Fear-calming facts: This condition is totally treatable. If it's picked up before 3 months, the success rate of a brace or harness is 95 percent. A baby under 6 months will most likely wear a harness for 6 to 12 weeks; some may require a cast, and an older baby may need corrective surgery. But, says Dr. Roye, the outcome after any of these approaches is excellent.

Bridget Gilfeather of Pleasantville, NY, had to be fitted with a harness not long after her 6-week checkup. "I was very upset, thinking of all the things she couldn't do, like go in the baby swing," says Bridget's mom, Mary. "Plus, she had to sleep with her legs up! But she adapted easily." By 9 months old, Bridget was out of the harness; by a year, she was walking.

Not gaining weight

Although babies typically double their birth weight by 4 months and triple it by 1 year, some experience "failure to thrive." Despite the horrifying (not to mention guilt-inducing) label, this diagnosis isn't nearly as ominous as it sounds.

Fear-calming facts: A swerve off the normal growth curve can happen for a variety of temporary, treatable reasons, says Andrea McCoy, M.D., chief medical officer at Jeanes Hospital, in Philadelphia:

A skimpy diet. A baby who's exclusively breastfed may not be getting her fill at each meal, but if she's the laid-back type and doesn't fuss about it, you won't know. Most likely, Mom's milk production is at an ebb for some reason (undereating herself? overexercising? stressed out?); a lactation consultant can help. Meanwhile, check with your doctor about supplementing with formula.

Gastroesophageal reflux. It's a mouthful -- just call it GER -- but it simply means a baby spits up so much that she doesn't down enough calories. Most infants do bring up a bit of dinner after eating -- the muscle between the esophagus and the stomach is loose, plus, young babies spend most of their time in a horizontal position, which makes it easier for fluid to flow back. By around 6 months, the muscle tightens, babies sit up more, and GER goes away (although some kids still spit up at 9 months and beyond). The fix until then: frequent burping, holding a baby upright for 20 minutes after she eats, and offering her small, frequent meals.

Genetics. A baby who was hefty at birth may lose ground on the growth chart as her first birthday approaches simply because she's programmed to be a slender person. But check with your pediatrician about any growth concerns.

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