Week 13 of Your Pregnancy

A look at your body, your baby, and more

Welcome to week 13 of your pregnancy—the last week of your first trimester. You’d think that something as basic as when a trimester begins and ends would be universally agreed upon. It’s actually not. Some experts mark this week as the start of your second trimester, while others count week 15 as the beginning. We’re taking the American College of Obstetricians and Gynecologists’ lead on this one and saying trimester number 2 starts next week.

week 13 pregnancy highlights
Illustration by Verywell

Your Trimester: First trimester

Weeks to Go: 27

You This Week

Your second trimester is just around the corner and, as a sneak peek, you may already be feeling less nauseated and exhausted, and experiencing a boon in energy. This next phase of pregnancy is generally considered the easiest. That said, don’t expect every not-so-pleasant pregnancy symptom to simply disappear at week 13. For some women, it's more of a gradual shift to feeling better. Either way, you are entering the least symptomatic phase of your pregnancy.

For some women, sexual desire returns right along with energy. If there are no extenuating circumstances (like placenta previa or vaginal bleeding), intercourse is generally considered safe throughout pregnancy. But know that you may experience some light cramping post-orgasm. This is nothing to worry about. Your uterus is simply mildly contracting.

Your Baby This Week

Baby’s head has been half the size of his or her whole body for a while now. But starting this week, things are getting a little more proportional, with baby’s head measuring about a third the size of his or her body. That said, your baby is still quite tiny at almost 3¾ inches (9.5 centimeters) long this week.

Baby’s skin is quite transparent and delicate, but now soft, fine hair called lanugo starts to cover it. (Down the road, the lanugo will help to keep a protective substance called vernix on baby’s skin, shielding it from amniotic fluid.) The tips of 10 tiny fingers now hold baby’s everlasting and unique fingerprints.

Your placenta is still growing and developing, providing your baby with oxygen and nutrients, and filtering out waste. It’ll be about five to seven weeks, however, until the placenta is fully formed.

At Your Doctor’s Office

If you did not see your healthcare provider for your second prenatal visit last week, you’ll likely be on your way this week. Here, your weight, blood pressure, and urine will all be checked. Your doctor or midwife will also use a Doppler—a handheld instrument that’s placed on your abdomen, over your uterus—to check your baby’s heart rate. With this, you’ll get to hear the precious thump-thump of your baby’s heartbeat.

Special Considerations

If you have a history of cervical insufficiency, sometimes called an incompetent or weak cervix, your healthcare provider may talk to you about getting a cervical cerclage between now and week 14 of your pregnancy. (This is considered the ideal timeframe in which to get the procedure.) Here, you’ll receive either general, spinal, or epidural anesthesia, while a surgeon stitches around the cervix to help prevent it from shortening and opening too early, causing preterm birth. The stitches can be removed in your healthcare provider’s office at 37 weeks.

Upcoming Doctor’s Visits

You’ve already had your first prenatal visit with your healthcare provider. Did you feel supported and listened to? Is your doctor or midwife responsive and respectful when you have questions or concerns? Know that if you don’t think your healthcare provider is the right fit, you have every right—even an obligation—to switch.

If you do decide to change providers, know that the process isn’t difficult. All you need to do is sign a release to transfer your medical records. If you don’t want to confront your healthcare provider face-to-face, simply have your new provider process the release.

Taking Care

You’re almost done with the first trimester—one of the biggest pregnancy hurdles. Since your nausea is very likely waning, now is a great time to start expanding your healthy eating choices. “This month is a great time to boost your intake of calcium, vitamin D, and magnesium, as each helps with baby’s rapidly developing bones and teeth,” says Dana Angelo White, M.S., R.D., assistant clinical professor at Quinnipiac University in Hamden, Connecticut and recipe developer for the book including The Whole 9 Months.

Healthy choices include:

  • Calcium: Dairy, fortified almond or soy milk, tofu, broccoli, and bok choy
  • Vitamin D: Egg yolks, fatty fish, and sardines
  • Magnesium: Raw spinach, squash, pumpkin seeds, avocados, soybeans, and lentils

For Partners

Some partners experience sympathetic pregnancy symptoms, also known as couvade syndrome, at the end of the first trimester. That’s right—you may be gaining weight or feeling queasy right along with your pregnant partner. The good news: According to a 2013 study in the journal Medical Science Monitor, the frequency of couvade symptoms is associated with empathy. So, if you’re not feeling the best, your not copy-catting for attention; you’re simply emotionally sensitive.

Verywell Checklist

  • Continue taking prenatal vitamins.
  • Continue drinking about eight to 12 glasses of water a day.
  • Take care to eat more foods containing calcium, vitamin D, and magnesium.
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