At 13 weeks, you’re now entering your final days of the first trimester. You can breathe a sigh of relief, as miscarriage rates greatly decrease after the first trimester. In fact, more than 80 percent of losses happen before the 12-week mark. Still, there’s a lot going on with both your body and your baby this week. Here’s what you can expect.

Changes in your body

changes in your body
Weight Gain at Week 13
Your first trimester is coming to a close. Gaining between 1 and 4 pounds is considered normal in a healthy pregnancy. For example, if you weighed 145 pounds when you became pregnant, you should expect to weight between 146 and 149 pounds this week.

As you enter your second trimester, your hormone levels are evening out as your placenta takes over production.

Your belly continues to expand up and out of your pelvis. If you haven’t started wearing maternity clothes, you might soon feel more comfortable with the extra room and stretch that those pregnancy panels provide.

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Your baby

week 13 baby

At 13 weeks, your baby has grown to roughly the size of a peapod. Its intestines, which spent the past couple of weeks growing in the umbilical cord, are returning to the abdomen. Tissue around your baby’s head, arms, and legs is slowly fortifying into bone. Your little one has even started urinating in the amniotic fluid. That may sound gross, but most of this fluid is actually made up of your baby’s urine from now until the end of your pregnancy.

In the next few weeks (usually by 17 to 20 weeks) you’ll likely be able to identify your baby’s sex via ultrasound. If you have a prenatal appointment coming up, you should easily hear the heartbeat with the use of a Doppler machine. You can purchase a similar machine for home, but be aware that they can be difficult to use and sometimes create more anxiety than relief.

Twin development at week 13

By the end of this week, you’ll have reached the second trimester! This week, your babies measure almost 4 inches and weigh just over an ounce. Tissue that will eventually become bone around your twins’ heads and their arms and legs is forming this week. Your little ones have also started urinating in the amniotic fluid that surrounds them.

Week 13 is a major milestone with singleton pregnancies, as the rate of miscarriage significantly lowers at the start of the second trimester. With multiples, this milestone is a few more weeks away at week 20.

13 weeks pregnant symptoms


This is when you’ll notice your earlier symptoms begin to fade and may find yourself in a comfortable state before fully entering your second trimester. Those of you plagued by nausea or exhaustion can look forward to diminishing symptoms in the coming weeks.

With these changes in symptoms some things to expect at 13 weeks include:

  • diminished nausea or exhaustion
  • increased energy
  • round ligament pain
  • leaky breasts

More energy

Besides round ligament pains and lingering first trimester woes, you should start feeling more energetic. Some call the second trimester the “honeymoon period” of pregnancy because most symptoms fade away. Enjoy this time when your belly is still small. Before you know it, you’ll be in the third trimester and dealing with a host of new complaints, like swollen ankles, back pain, and restless sleep.

Round ligament pain

At this time, your uterus is continuing its rapid growth. You should be able to feel the top of it just above your pelvic bone. As a result, you may start to experience sharp lower abdominal pains called round ligament pain when you get up or shift positions too quickly. In most cases these sensations are harmless. If you have pain in combination with fever, chills, or bleeding, call your doctor.

Leaky breasts

Your breasts are also changing. As early as the second trimester, you’ll start producing colostrum, which is the precursor to breast milk. Colostrum is yellow or light orange in color and thick and sticky. You may notice your breasts leaking from time to time, but unless you have pain or discomfort, it’s just another perfectly normal, albeit annoying, part of pregnancy.

Things to do this week for a healthy pregnancy


If you’ve been feeling sick up until this part of your pregnancy, don’t fret. It’s never too late to start healthy eating habits that will nourish your body and your baby. Focus on whole foods that contain lots of vitamins, minerals, and good fats. Whole grain toast with peanut butter is a solid way to start the day. Fruits high in antioxidants, like berries, make a wonderful snack. Try incorporating lean protein from beans, eggs, and oily fish into your meals as well. Just remember to steer clear of:

  • seafood high in mercury
  • raw seafood, including sushi
  • undercooked meats
  • lunch meats, though these are generally considered safe if you heat them up before eating
  • unpasteurized foods, which includes many soft cheeses
  • unwashed fruits and vegetables
  • raw eggs
  • caffeine and alcohol
  • some herbal teas

Exercise is still recommended if it’s been cleared by your doctor. Walking, swimming, jogging, yoga, and light weights are all great options. At 13 weeks, you should start finding alternatives to abdominal exercises, like sit-ups, that require you to lie flat on your back. The increasing weight from your uterus can decrease blood flow to your heart, making you lightheaded and, in turn, slowing the delivery of oxygen to baby.

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When to call your doctor


Always contact your doctor about any pelvic or abdominal cramping, spotting, or bleeding, as these may be signs of miscarriage. Likewise, if you are experiencing anxiety, depression, or excessive stress, it’s a good idea to seek help sooner rather than later. In a review published by Current Opinion in Psychiatry, these issues are highlighted as contributing factors to low birth weight, preterm birth, and postpartum depression.

Onto the second trimester

Though some books and reports disagree over the exact start of the second trimester (between 12 and 14 weeks), rest assured that by next week you’ll be in undisputed territory. Your body and baby are continually changing, but you’re entering some of the most comfortable weeks of your pregnancy. Take full advantage. Now is a good time to schedule any last minute trips or adventures you want to embark upon before you have your baby in tow.