Let's face it, it's a tough time to be pregnant.

We're expected to dress for success (pin-striped maternity business suits), avoid every pleasurable substance known to man (I'm sure someone is going to discover that hair mousse crosses the placenta) and stay in better shape than Mary Lou Retton.

Some expectant mothers seem to be training for the triathlon: bicycling, swimming, jogging, swinging from parallel bars and pumping more iron than Pittsburgh.

Since not enough research has been done on the effects of strenuous exercise on the fetus, and since there's no scientific proof that active mothers have it any easier in the delivery room than their sedentary sisters, most obstetricians will offer the same scant advice: pregnant women can continue most exercise programs they have already mastered, although at a reduced rate, and are cautioned against starting any new ones.

Now there's more information, thanks to the American College of Obstetricians and Gynecologists, who have produced a home exercise videotape with the help of the NBC "Today" show's Dr. Art Ulene.

Obviously designed to get a toehold on Jane Fonda's vastly successful "Workout" empire, Ulene's entry, available in VHS and Beta for about $40, is a moderate stretch and relaxation program starting with a typical aerobics warm-up and ending with a deep-breathing session.

First, I reviewed Fonda's tape, "Pregnancy, Birth and Recovery" then compared it to Ulene's. I don't know why I ended up feeling safer in the hands of a radical actress than the American College of Obstetricians and Gynecologists, but I did.

Ulene's tape is slicker than Speed-Stick, with custom-penned disco tunes like "Labor of Love" and "Something's Growing." The women wear shiny sherbet-colored leotards and are perched precariously on what look like giant Alka-Seltzer tablets. We never learn the identity of the teacher until the end (Kimberly Dashiell), and since she herself is nine months pregnant, her figure is more distracting than Fonda's, her movements often ungainly.

The pace of Ulene's warm-up seems rushed, the changes too abrupt. The waist and arm exercises are standard fare, and the leg strengtheners seem helpful (Fonda refrains from any maternity leg lifts), but the hastily demonstrated movements are never adequately explained.

The tape is interrupted several times so participants can take their pulse, a gimmick that seems to distract rather than instruct. Ulene warns that pregnant women should not allow their heart rate to exceed 140 beats per minute. As any pregnant woman past her sixth month knows, it's pretty hard to work up that much steam for anything other than jogging to the pastry cart.

Many women who exercise to videotapes say the main drawback is boredom from watching the same tape over and over. If the budget will allow, expectant mothers may find Ulene's tape and its bulging instructor a welcome addition.

If only for those times when you just can't bear to watch Fonda and her flat stomach.