For the mother, the cardio helps keep the body in a state where it is more apt to move into a fat loss state after the birth. It also improves circulation and all around health.
So Id say a 60/40/20 plan would be good, and for the sake of sanity, go on out once a week and eat something fun, not smart! Hell, it actually helps stimulate your metabolism by waking it up!

I agree with monster in that pregnancy is not a time to think about weight loss. It is only nine months compared to the rest of her life. To improve her eating habits and continue to be active is VERY WISE for both mother and baby. I'm sure your friend already knows (as this is her second time around) how quickly she will become encumbered by the rapidly growing fetus and since she has not yet shed the weight gain from her first pregnancy I'm sure that her older child is probably not much older than a toddler. By eating better, getting adequate rest and continuing to be active, keeping her body strong - she will be able to get through this pregnancy with more ease and be better able to "chase after" her older child.

I'm no doctor, but I do have my own experience. I was only inactive during my third pregnancy (no $ for gym and renovating home so I was basically confined to 2 bedrooms and bathroom for 7 months - with two small children!...by the renovations were done I was too damned big and miserable to care about exercise.) and it was the time when I gained the most weight (35#) and felt the most miserable!

The better I ate, the more active I was - the better I felt - simple equation.

The article is at RenegadeBodyBuilding.com under articles--it's actually an article about insulin use, but the relevant part here is under the sub-section "One more Explanation: Insulin and Fat". Here's the most relevant part:

"The reason why some people are fatter than other's isn't the size of fat cells but the number of fat cells. Though many columnists gladly point to a sedentary society and the readily available quantities of food in today's "age of convenience" as the underlying cause of increased obesity, I won't take the easy way out. Obesity is genetic. But how could so many of us mutate in the last 40 years? If TV has been bombarding us with a high order of radiation as yet undiscovered, and mutations ran rampant, why did so many of us mutate into fat people? Why not an extra arm or mouth or something more useful for survival in this age?

Elevated insulin in the blood of the fetus causes preadipocytes to differentiate at an accelerated rate. What causes elevated insulin in the fetus? Elevated insulin levels in the mother. This encourages paired insulin antibodies to cross the placental barrier. Mother's who throw caution to the wind and eat all they want for the good of the baby really aren't doing the baby any favors, especially with a high carbohydrate (sugar/starch) diet. When the baby is born with two to three times the normal number of fat cells, its fat(e) is pretty much sealed."

I think Monster's plan is a good one, along with mild exercise. She will also need to support her milk production after the baby is born so she shouldn't plan on going on a calorie restricted diet immediately after the birth if she's planning on breast feeding. I've read that 300-500 cal add'l is about right to support milk production after the baby is born.

Wish her luck for me!

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LAte