While all of this may sound overwhelming, in most cases there’s a lot you can do to keep your weight gain under control (plus, of course, your doctor will be there to guide you). Here’s some important info to keep in mind to gain a healthy amount of weight during pregnancy.

Understanding your BMI

You may have heard the often-repeated 25 to 35 pounds as the suggested weight gain goal range for women during their pregnancy, but that’s directed at women whose Body Mass Index, or BMI, falls into the “normal weight” category. Your BMI is calculated by your height and weight. The first step to determining your personal weight gain goal is to determine your BMI.

How much weight to gain and when

Unlike the equation used to calculate your BMI, the process of putting on pounds is not an exact science. Your rate of weight gain will depend on a variety of factors, such as your metabolism, your activity level and your genetics — just another reason why it’s important to keep up your doctor appointments throughout your pregnancy. That said, the American College of Obstetricians and Gynecologists (ACOG) offers general weight gain guidelines based on various BMI ranges (see chart below), which vary by trimester:

• During your first trimester, your baby is still tiny, which means you don’t need to gain more than a total of three to four pounds. However, if you’re suffering from morning sickness, you might not gain an ounce (or might even lose a little). That’s OK, as long as your appetite picks up and you make up for those pounds in the second trimester.
• In your second trimester, your baby starts to grow in earnest. Your weight gain should pick up so that, if you started your pregnancy at a normal weight, you’d gain a total of about 14 pounds.
• In your third trimester, baby’s weight gain will pick up steam, but yours may start to taper off for a net gain of about 10 pounds. Some women find their weight holds steady or even drops a pound or two during the ninth month, when ever-tighter abdominal quarters can make finding room for food a struggle.

Gradual weight gain is as important as the number of pounds you gain, since your baby needs a steady supply of nutrients and calories to grow during his or her stay in the womb. The amount of weight you should gain each week in trimesters two and three differs depending on your BMI: If you’re carrying twins, the weight gain recommendations for women of an average weight is 37 to 54 pounds. Overweight women should gain 31 to 50 pounds, and obese women should gain 25 to 42 pounds.

How closely will you be able to follow this formula? Realistically, not that closely. There will be weeks when your self-control will waver and it’ll be a rocky road (by the half gallon) to your weight gain total. And there will be weeks when eating will seem like too much of an effort. Try not to stress over the scale. As long as your overall gain is on target and your rate averages out to the above, you’re right on track.

Where’s the weight going?

Ever wonder how your pregnancy weight is distributed in your body? It may feel like it’s all in your belly, but that’s not actually the case. For a 30-pound weight gain, here’s the approximate breakdown:

• Baby: 7.5 pounds
• Placenta: 1.5 pounds
• Amniotic fluid: 2 pounds
• Uterine enlargement: 2 pounds
• Maternal breast tissue: 2 pounds
• Maternal blood volume: 4 pounds
• Fluids in maternal tissue: 4 pounds
• Maternal fat stores: 7 pounds

You need weight in all these areas in order to have a healthy baby and to get your body ready for motherhood (including preparing your body for nursing).

Weighing yourself

For the best weight gain results, keep an eye on the scale — what you don’t know can throw your weight way off-target. Try to weigh yourself:

• At the same time of day
• Wearing the same amount of clothes (or none at all)
• On the same scale
• Once a week (more often and you’ll drive yourself crazy with day-to-day fluid fluctuations; if you’re scale-phobic, try weighing yourself twice a month)

Waiting until your monthly prenatal checkup to check your weight is fine, too — though keep in mind that a lot can happen in a month (as in 10 pounds) or not happen (as in no pounds), which can make it harder for you to stay on track.

How many calories should you eat?

The key to healthy pregnancy weight gain is eating a well-balanced pregnancy diet. That means some not-so-fun news: The expression “eating for two” is a myth — or at least an exaggeration. (Sorry!) Instead of doubling your caloric intake, you likely won’t need any more calories in the first trimester. In the second trimester you should add about an additional 300 calories per day, and in the final trimester of your pregnancy you’ll need about 500 calories more per day than you were eating before you conceived. As a rule, instead of just eating more, focus on eating nutrient-rich foods that will give you energy, help keep morning sickness at bay and fuel all of the incredible fetal development going on inside of you, from fetal bone growth to cognitive development to the formation of your baby’s skin, eyes and digestive system.

Keep in mind, too, that if you have a fast metabolism are very physically active or are carrying multiples, you may gain weight more slowly and will need to eat more calories. And if you were overweight or obese before you got pregnant, you may not need as many calories. As always, it’s important to check with your practitioner to get a personalized recommendation on your caloric and weight gain goals.

Weight gain red flags

If you gain more than three pounds in any one week in the second trimester, or if you gain more than two pounds in any week in the third trimester — especially if it doesn’t seem to be related to overeating or excessive intake of sodium — check with your practitioner, as it could be a symptom of preeclampsia. Check, too, if you gain no weight for more than two weeks in a row during the fourth to eighth months.

Will all that weight ever come off?

Many women fear that they won’t be able to lose the weight they gain during pregnancy once baby is born, but there’s no need to stress about it. There are lots of healthy ways to lose weight after pregnancy — and many of them are also great ways to meet other new moms (like stroller walking groups or baby-and-me yoga classes). Many gyms offer childcare for babies as young as 3 months old, which is a great way for you to boost endorphins and get a break from your little one — both of which can help keep the baby blues at bay. On top of that, many women are shocked at how quickly they are able to lose the pounds by breastfeeding alone (women who breastfeed for even a few months tend to lose weight faster than those moms who don’t at all). Just remember, gaining the right amount of weight (and not too much) during pregnancy makes it a whole lot easier to shed the pounds once baby arrives.