Before her pregnancy, Jennifer Lucero of Mountain House, Calif., hit the gym four days a week. She'd lift weights. Ride the elliptical. But once she was expecting, Lucero, who is also a vegetarian, wondered if she'd have to adjust her workout and possibly her diet, especially according to the theories of her parents and grandparents.

"I knew I'd definitely hear it from everyone about iron and meat for the baby," says Lucero, who is nearing her due date.

But when she consulted her obstetrician, she was encouraged to change very little. She cut her gym visits by two days and replaced them with yoga and walking. Her diet - rich in yogurt, almonds and eggs - remained the same.

Smoking and alcohol are well-known no-nos. But navigating the rules of diet and exercise during pregnancy can be tricky, especially with conflicting advice from family, midwives, the medical community and the media, with images of celebrity moms-to-be, their personal trainers and barely-there bumps. While experts agree that traditional ideas such as eating for two and limiting cardiovascular exercise are passe, they encourage women to adjust the suggested guidelines of weight and nutrition to their own lives, and what they did before pregnancy.

Miyoko Sakashita of Oakland, Calif., is a lifestyle cyclist and continued biking through her 39th week. She also stuck by her other passion, surfing, until her belly was too big to lie on the board, she says.

"It's a good thing that wetsuits are stretchy," Sakashita says.

As her belly grew, Sakashita learned how to paddle on her knees, and surfed until her last trimester. Even then, she tried stand-up paddleboarding. As for eating, Sakashita kept her pre-pregnancy balanced diet and simply added breakfast.

"I almost got healthier," she says. "My midwife told me to just eat a little more of what I already ate."

That's the standard, according to clinical dietitian Nora Norback of Kaiser Permanente Richmond. Calories should increase by 100 to 300 per day, depending on the pregnancy, Norback says. The foundation is the same as any balanced diet: whole grains, fruits and vegetables, nonfat or lowfat dairy products and lean proteins. Most women gain 25 to 35 pounds during pregnancy, but some can gain as little as 15 or as much as 40 pounds.

"Obviously it depends on if you're having twins or were underweight or overweight to begin with," she says.

Together, Norback and obstetrician-gynecologist Betty Lin monitor the health of Beatriz Ramirez, a San Pablo, Calif., mother of two who is expecting her third.

In her first pregnancy, Ramirez gained 80 pounds and ate whatever she craved.

"I was going to gain the weight so I figured I might as well enjoy it," says Ramirez, adding that she consumed a lot of takeout, particularly Mexican food.

During her second pregnancy, Ramirez was calorie-conscious.

"I was very scared to gain weight so I was cautious of what I ate and how much I ate," she says.

This time around Ramirez, who is glucose-intolerant, weighed 245 pounds before her pregnancy, and was advised to gain no more than 10 pounds over the nine months. But she has already gained 30. Ramirez comes from a long line of diabetics, so the clinicians have recommended she limit her carbohydrates to ward off the disease.

Calorie restriction was suitable for Ramirez, who was considered overweight by her doctors. But for some pregnant women, excessive dieting, exercise and purging are signs of an eating disorder, often referred to as pregorexia. Norback estimates that up to 4 percent of child-bearing women may have an eating disorder, and that it is often relapse anorexia or bulimia. Calorie restriction puts the baby at risk for premature birth and low birth weight, respiratory difficulties and birth defects. It also increases the mother's risk of postpartum depression.

"We try to remind the patient that pregnancy is about health, and the health of their baby, not about body image," says Norback, who tracks patients through Kaiser's network-wide Health Connect system. Lin looks for warning signs, such as weight loss in the second trimester, which is when morning sickness usually ends. She also checks for body mass index, electrolyte abnormalities and dental problems that result from induced vomiting.