Weight Watchers and Pregnancy Don't Go Together — Here's Why

Pregnancy is an exciting time, with thoughts of a sweet baby to cuddle and adorable outfits to buy. But along with all the joy can come significant weight gain, which can lead to complicated feelings. So you may be wondering: Can you do Weight Watchers while you're pregnant?

Since the 1960s, Weight Watchers (recently rebranded as WW) has been one of the top weight-loss programs, offering tools, motivation and education to help participants make the right decisions about food and exercise. So if you're trying to reach a healthy weight ​before​ you conceive or want to drop a few pounds ​after​ delivery, Weight Watchers might be of great help.

However, if you are currently pregnant, know this: Weight Watchers is not for you. "Dieting is not recommended during pregnancy as it can compromise the integrity of mom ​and​ baby's nutritional status, which can ultimately lead to severe health conditions or long-term consequences," explains Monique Richard, RD, an integrative dietitian nutritionist and owner of Nutrition-in-Sight. Even WW states on its website that to enroll in the program, you must "not be pregnant."

Pregnancy is not the time to start restricting your caloric intake. Babies need nutrients from your diet to grow and develop. "The fetus relies on mom's nutrition to meet its growing needs — and diets are often restrictive and prohibitive, so they're not beneficial to a healthy, happy baby and resilient mom," notes Richard.

According to the American College of Obstetricians and Gynecologists (ACOG), if you have a body mass index, or BMI, in the normal range, you'll need an extra 300 calories or so a day during pregnancy (and about 600 more calories if you're carrying twins). Get these calories from nutrient-dense foods such as fruits, vegetables, whole grains, lean protein and healthy fats.

Pregnant women specifically need iron, calcium, vitamin C, folate (B9) and omega-3 fatty acids, as these nutrients are important in forming a healthy brain and spinal cord as well as making DNA and genetic material, explains Richard. "If a diet restricts whole grains and other food groups and doesn't account for variety and adequacy, these nutrients can be under-consumed or consumed at inadequate levels," she warns.

​Read more:​ What to Expect with Pregnancy, Week by Week

The most recent weight-gain guidelines for pregnancy were introduced in 2009 by the Institute of Medicine (IOM), reports the American Pregnancy Association. Recommended weight gain during pregnancy is based on your weight before pregnancy. Using this number, your doctor can calculate your pre-pregnancy BMI.

A BMI between 18.5 to 24.9 is considered normal weight. If you were at a normal weight before becoming pregnant, IOM recommends you gain 25 to 35 pounds. Any BMI less than 18.5 is classified as having underweight, so IOM recommends a gain of between 28 and 40 pounds. If you have a BMI of 25 or more, the recommendation is to gain only 11 to 20 pounds.

That said, these are only guidelines. Women and their care providers should use these numbers in the context of a larger discussion about healthy eating and exercise.

​Read more:​ 5 Ways to Tone Up During Pregnancy and Stay Fit

Women should never lose weight during pregnancy, but there's one rather unavoidable (and uncomfortable) exception: morning sickness. This very common condition, which is marked by nausea and vomiting, affects up to 80 percent of expectant moms. It may result in a little weight loss and, despite its name, can strike morning, noon and night. Morning sickness usually begins around week nine of pregnancy and lasts into the second trimester, subsiding by week 14, though some women experience it even longer, per ACOG.

Very severe morning sickness, known as hyperemesis gravidarum, can affect about 3 percent of pregnancies, according to ACOG. This condition is diagnosed when a woman has lost 5 percent of her pre-pregnancy weight and is experiencing complications due to dehydration. If the vomiting can't be controlled, fluids and vitamins may be given intravenously or medication may be prescribed. "A case like this may require medical attention due to electrolyte imbalance, changes in blood pressure or hydration status," says Richard.

Gaining weight too quickly during pregnancy may lead to problems for both you and your baby, including premature birth, labor complications and fetal macrosomia, which is when a baby is born at more than 8 pounds 13 ounces, according to the March of Dimes. A baby this large may require a C-section and could cause excess bleeding after birth.

The healthiest way to gain weight during pregnancy is the slow and steady approach. So the takeaway here is to focus on eating healthfully and staying active.

Bottom line? You should never go on a diet during pregnancy, including Weight Watchers. If you feel that you are gaining too much weight with your pregnancy, consult your doctor so you can come up with an eating and activity plan that works best for you.