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13 Weeks Pregnant—Welcome to the Honeymoon of Pregnancy

Welcome to the second trimester, often referred to as the “honeymoon phase” of pregnancy. You’re feeling fewer pregnancy symptoms and may notice an increase in sex drive. Now about the size of a lemon, your baby continues to rapidly grow and develop.

How big is my baby?

Baby’s Length: 2.91 inches.

Baby’s Weight: 0.81 ounces.

How is my baby developing? 

Your baby’s intestines have been growing for the last few weeks inside the umbilical cord. This week, they will return to his belly, where they’ll continue to develop. He’s also creating urine and releasing it into the amniotic fluid. His eyes are moving closer together, his ankles and wrists have formed, and he has vocal cords, teeth, and fingerprints.  

Though some of your baby’s bones have already hardened, tissue around his head and within his arms and legs is still forming and will eventually become bone. His head is still quite big but the rest of his body is beginning to catch up. Though his legs need more time to grow, this week his arms will lengthen proportionally. He’ll even be able to suck his thumb. If your baby is a girl, she already has over two million eggs in her ovaries!

Though development has been relatively uniform up to this point, starting next week, fetuses will begin growing at different paces.

What’s happening in my body? 

As you move past the first trimester and nausea subsides, you may find yourself hungry again—and actually able to eat. Especially if you were hit hard with morning sickness, you may begin to reliably gain weight during the second trimester. Before you go all in at the eating-for-two buffet, it’s important to remember that, while gaining weight is an important part of pregnancy, that weight should be accomplished as healthily as possible. The American College of Obstetricians and Gynecologists (ACOG) suggest the following guidelines:

woman in bed

If you’re underweight (a BMI* under 18.5):

  • 28 to 40 pounds is your total recommended weight gain.
  • Aim to gain about a pound (1 to 1.3 pounds, to be exact) per week in the second and third trimesters.

If you’re average weight (a BMI of 18.5 to 24.9):

  • 25 to 35 pounds is your recommended total pregnancy weight gain.
  • Aim to gain about a pound or a little less (0.8 to 1 pound) per week in the second and third trimesters.

If you’re overweight (a BMI of 25 to 29.9):

  • 15 to 25 pounds is your recommended total pregnancy weight gain.
  • Aim to gain a little over a half pound (0.5 to 0.7 pounds) per week in the second and third trimesters.

If you’re obese (a BMI of 30 and above):

  • 11 to 20 pounds is your recommended total pregnancy weight gain.
  • Aim to gain about a half pound (0.4 to 0.6 pounds) per week in the second and third trimesters.

If you’re 13 weeks pregnant with twins:

  • 37 to 54 pounds is your recommended total pregnancy weight gain.
  • During the first half of your pregnancy, aim to gain about a pound per week. In the second half, aim to gain a little over a pound per week.

*To calculate your body mass index (BMI), multiply your weight in pounds by 703 and divide that number by your height in inches.

You may also notice an increase in your sex drive during the second trimester, though this doesn’t happen for all pregnant women. Remember that a little spotting after sex is normal because of your sensitive cervix, but if you experience heavy bleeding, contact your doctor.  

Your uterus is continuing to grow up and out of your pelvis, which means you’ll start to look pregnant around this time. Though your baby won’t be here for six more months, your breasts have already started making colostrum. This “liquid gold” is a nutrient-rich precursor to milk; your baby will only need colostrum in the first few days of life.

If you haven’t noticed visible veins yet, that may change around now. You have so much increased blood flow, your body’s veins have grown to accommodate it. This excess volume also accounts for the sudden dizziness you might feel if you stand up too quickly.  If you’re feeling clumsier than usual these days, you have another hormone to blame: relaxin. As you may be able to guess from the name, relaxin works to relax and loosen your joints and ligaments before birth. Though your pelvis is the only part of your body needing the extra stretch, relaxin works on your whole body. Since it’s active in your hands and feet, it’s likely the reason you’re dropping things or stumbling more frequently.

All of this said, don’t be alarmed if some of your pesky first-trimester pregnancy symptoms linger. The second trimester doesn’t provide a get-out-of-symptoms free card. Some women have persistent morning sickness into the fourth and fifth months of pregnancy (and some unfortunate women have to deal with nausea the whole way through).

What should I be doing?

Pay attention to how much water you’re drinking. The Institute of Medicine recommends you drink eight to twelve eight-ounce glasses per day.

While you’re eating your healthy extra calories (about 300 per day), consider adding foods rich in calcium, magnesium, and vitamin D to help sustain your baby’s rapidly growing teeth and bones.

Start a prenatal fitness class, like yoga or water aerobics. If you haven’t been active previously, check with your doctor before starting a fitness regime.

Avoid exercises like crunches or sit-ups that require abdominal twisting or lying flat on your back.

Don’t forget to keep up with your dental check-ups. About 80% of expectant moms suffer from gum bleeding or softening.


Lindsay Meisel

Lindsay Meisel is the Head of Content at Ava. She has over a decade of experience writing about science, technology, and health, with a focus on women's health and the menstrual cycle. Her work has been featured on The Fertility Hour, The Birth Hour, The Breakthrough Journal, and The Rumpus.

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