「Pregnancy means eating for two」

Where the claim comes from

"Eating for two" sounds self-evident, and older relatives often show care through portion sizes. But the extra energy pregnancy requires is nowhere near a second helping.

What the evidence says

For women who were a healthy weight before pregnancy, the American College of Obstetricians and Gynecologists (ACOG) gives these figures: in the first trimester (the first 12 weeks) weight gain is minimal and usually no extra calories are needed; in the second trimester you need about 340 extra calories a day, and in the third about 450. As for weight, you may gain only 1 to 5 pounds (about 0.5–2.3 kg) in the first trimester, or none at all, and between half a pound and 1 pound (about 0.2–0.5 kg) a week in the second and third. How much to gain overall depends in part on your body mass index (BMI) before pregnancy.

What to do instead

• Those few hundred calories amount to roughly one extra snack, not double portions at every meal.
• Increase gradually — ACOG's phrase is that the key to healthy weight gain is to slowly increase your calories.
• Ask your prenatal care provider for a weight-gain range based on your pre-pregnancy BMI, and check against it at each visit.