Q: How risky is it to travel by air with a 2- to 4-month-old? Are there reliable statistics on infections? — Via e-mail 

A: Airplanes confine large numbers of people in a small space. Along for the ride are airborne infections — usually mild ones resulting in coughs, colds and sore throats.

Statistics on babies’ on-board risk are hard to gather. An infant may have picked up a common infection before or after flying. Sometimes a rare infection can be traced to a fellow passenger.

Babies aren’t defenseless. Newborns’ blood contains antibodies transferred from their mothers’ blood through the placenta. These antibodies, persisting for roughly the first three months, help babies fight back. So until 3 or 4 months of age, babies may be better protected than during the next few months, when their bodies are developing their own defenses against infection.

Breast-fed babies receive another shield: Breast milk contains the mother’s antibodies. Vaccinations also safeguard babies.

Although no parent wants to expose a baby unnecessarily to risk, a healthy baby should be able to fight off a mild infection and recover rapidly.

Parents of babies with risk factors will want to take extra precautions. Babies with immune system deficiencies or cystic fibrosis, and babies born prematurely, are likely to be more vulnerable to respiratory infections. Ask your pediatrician for advice.

In certain seasons, airborne, respiratory infections circulate at higher rates than usual. Flu season runs from autumn through winter. For young babies, respiratory synctial virus is a frequent cause of lung and bronchial infections during winter months.

If you must travel by air, be sure your baby drinks plenty of fluid during the trip. Pack extra diapers. Breast-feeding mothers need to drink plenty of water too.

Be sure to let your baby nurse or suck from a bottle during takeoff and landing. This will help open up the tiny Eustachian tubes from the middle ear to the back of the mouth that equalize the pressure in the middle ear.

Often when babies cry during takeoff and landing it is because the pressure in their middle ears is building up. Sucking and swallowing can help.

Avoid contact with anyone who is sneezing or coughing. A baby pouch — with the baby facing you, and a thin blanket loosely arranged for adequate air circulation — can help protect airspace from others’ coughs and sneezes.

Before you fly, find out how to reach your pediatrician’s office after hours. It’s also a good idea to tell a pediatrician where you are traveling — just in case a disease alert is in the offing. Your pediatrician may be able to make a referral. And bring a baby first-aid kit, including a thermometer and infant acetaminophen or ibuprofen to use at the pediatrician’s direction.

Send questions to The New York Times Syndicate, 620 Eighth Ave., 5th Floor, New York, N.Y. 10018 or by e-mail to:

[email protected]