For nine months, Jack looked forward to the arrival of a new baby in his family. After his mom told him she was pregnant, he thought about the baby often, wondering what it would be like, and thinking up things to do when his brother or sister arrived.

"I'll help teach the baby how to walk," he told his mother one morning. "And when you're making breakfast in the morning, I'll watch him to make sure he's safe."

"Why are you so sure the baby's a boy?" his mother asked.

"I have a feeling about it," Jack said. "A girl would be fine, too. Or twins!"

"The doctor told me I'm not having twins," his mom said. "Sorry."

Jack has met his mom's doctor, a special kind of physician called an obstetrician. Months before the baby was born, when his mom didn't even look all that pregnant, Jack went along on one of her appointments. The doctor asked him into the office, and let him listen to the baby's heartbeat through a stethoscope. After that, Jack felt closer to the baby.

Most of the time, the idea of having a new person in his family made Jack feel good. It would be nice to have someone to talk to, to watch TV with, and to fool around with someday. But there were times when Jack felt confused about the baby. Sometimes he felt almost mad at it, even though the baby wasn't born yet. Sometimes he worried that the baby would keep his mom so busy that she wouldn't have any time left for him. Would she still be able to be the official scorekeeper at his softball games? Would she still make cupcakes for his class at school on special occasions?

Jack wasn't quite sure how to ask his mom these questions. He didn't want her to think he wasn't excited about the baby. So for a long time he didn't say anything about his worries. But the questions kept coming up in his mind.

Jack's father noticed that his son was being a little quieter than usual. He decided to take Jack out for dinner. They had hamburgers, and talked about all sorts of things. They didn't even mention the baby until they were having dessert.

Then Jack's father said, "You know, before you were born, I was really excited. I couldn't wait to be a father. But sometimes I felt a little funny about it. I wondered if your mom would pay as much attention to me after the baby was born. But I found out that your mom had time for me and for you."

Jack felt better all of a sudden. He felt like he wasn't the only person in the world who could be jealous of a tiny baby.

"Having confused feelings about a new baby is very common," says Brenda Vallana. She runs a special program called "It's a Small Wonder" at Frederick Memorial Hospital in Maryland. At her class, families talk over their feelings about having a new baby. They watch a video called "Our family is changing in a special way." They practice baby care, and make presents for the newborns.

"Older brothers and sisters are just as important as the new baby," Vallana says.

Not so long ago, children weren't allowed to visit mothers and new babies in the hospital. But today many hospitals allow -- and encourage -- brothers and sisters to come in and get acquainted as soon as possible.

At the hospital where Jack's mother planned to deliver her baby, they invite kids to tour the maternity unit before the baby arrives. That way, they'll know what the place is like. When Jack visited the hospital, he saw the glass-walled room where all the new babies lie in their beds asleep -- or crying! He saw mothers and fathers walking the the hallways, and he saw other kids his age visiting their new brothers and sisters. Even though he felt a little nervous, he wished that he was already one of those kids looking through the window at a new brother or sister.

"There he is," one girl yelled when she first saw her brother. "He looks just like I did when I was a baby."

Jack wondered how the girl knew what she had looked like. He figured she must have seen pictures of herself. All the babies looked alike to him.

But when Jack visited the hospital again a few days later, and got his first look at his brother Luke, he thought Luke was the best-looking baby there. "All the other babies look kind of scrawny," Jack told his mom. "But Luke looks like he's going to be a great softball player."

"I'll bring him with me when I keep score at your games," his mom said. "That way he'll get an early start."

Next Week: When a baby is born too early. Tips for Parents

Brenda Vallana, an early childhood educator who runs the "It's a Small Wonder" groups at Frederick Memorial Hospital, offers these tips to help your child get involved in a new baby's arrival: * Have your child make the baby a welcome home present. Vallana's classes make bibs. * Take a picture of the older child to the hospital and put it in the baby's bed so the newborn can "see" his older sibling. * With the older child, bake a birthday cake. Freeze it, and when you bring the newborn home, defrost the cake and have a party for the baby. * Don't exaggerate the idea that the new baby will be a playmate. The older child should be aware of the newborn's limitations and the demands it will make on everyone's time.

Catherine O'Neill is a contributing editor to the Health section.