Q: I am delighted to be pregnant with our second child.

My main concern now is helping our 3-year-old daughter cope with the event.

She is bright, verbalizes well and is generally a cooperative and adaptable child. However, she always has displayed an inordinate amount of jealousy--more tears of heartbreak than of rage--toward any small child to whom I show any attention.

Because she is getting better now in such things as sharing favorite toys, we want to keep her on the positive side after the baby arrives. What can we do?

A: A child is a marvelous invention.

She has the energy of a hummingbird, the appeal of a puppy, the beauty of a daffodil--and the intuition of a mind-reader, especially where she is concerned.

You're alarmed at her rebellion?

She's going to be sassy.

You shudder at her tantrums?

She's going to throw some lulus.

You're anxious about her shyness?

She'll be even more withdrawn.

This is the way it goes in all areas and in all relationships. We give others the weapons that will hurt us most and sooner or later they're usually used. This is what you're probably doing now, and she senses your concern.

When a new baby is due, the old one is bound to get anxious and a little jealous, but the degree of her anxiety and jealousy will depend on the signals you send and how strong they are.

The more you hover around her and try to reassure her, the more she will think something is so wrong she needs reassurance. You'll do this less if you remember that another baby is obviously a good decision for you and your husband. And if it's good for you, it will be good for your daughter.

There are advantages in every kind of family, whatever the sex of the children, the number or the spacing. Consider:

* An only child is best because she doesn't have to share her parents and they aren't pulled in too many directions.

* Two children are best because they're pals to each other and a pleasure to their parents: a boy for you, a girl for me, or two girls (because they can share their clothes) or two boys (who can go fishing together).

* Three children are best because they have to be more independent and because their mother becomes so efficient (it's either sink or swim).

* And four children are super, because that's what I've got.

And so it goes.

Whatever you have is right, until you decide to have another baby. Then the rationale changes and you remember that an only child can get mighty lonely; that two children can get too competitive and that if three can be so great--and they are--then four must be even better.

And all of those reasons are right, and many more.

There is a positive side of everything, and if your family is going to get along smoothly, you have to see the best in life so you can deal with the rest.

The fine part of having another baby now is that it really is great spacing. The bonding to your firstborn is strong, you're long recovered from the fatigue of the first two years and you know what the effects of your discipline will be--most of the time.

It also is good for your daughter to have another child to love and to protect, to share toys and good times.

Right now she needs you to minimize the talk of a new baby (whether she mentions it or not, she's quite aware of it) and emphasize the joys of a 3-year-old.

You do this when you help her grow up before the big event, by following a basic law of nature. Every pregnant female automatically boosts the littlest from the nest, which you'll do best by encouraging your child to be more independent. When you praise her openly for her sense of responsibility, invite her to cook or garden with you because she's "such a help" and talk with her about your news as if she were a grown-up, she realizes that babies don't get all the breaks.

There still will be cuddling--and an extra amount of it after the baby is born--but even then she will need less if you encourage her to help you take care of the baby quickly, so you can have more time together.

Experience will help you make better use of your time: You'll learn to do the family chores quicker and also learn what kind of attention matters most. You will have many middle-of-the-night visits with the baby when you nurse and many hours in the day when your daughter is in nursery school or playing with friends. Even if you couldn't give as much time to the baby as you gave your first child, the new one wouldn't know any better.

Despite this careful orchestration, your daughter is sure to feel some sense of displacement, especially after the baby is about three months and full of attention-getting coos and goos. The only child pays a price when she becomes the older one.

Fortunately, she will be the richer for it and she'll know this, most of the time. In the process she'll learn that the best things in life aren't really free, but they sure are worth it.

Questions may be sent to Parents' Almanac, Style Plus, The Washington Post.