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13 Weeks Pregnant: Week by Week Pregnancy

Symptoms, Tips and Fetal Development


You're pregnant at 13 weeks – welcome to the second trimester, aka the Golden Age of Pregnancy! Many women feel a sense of relief now that the first trimester is over and the chance of pregnancy loss is greatly diminished. 

Over the course of this trimester, your baby’s growth will take off, and s/he will triple in size! There’s still plenty of mental development happening as well. The first half of the second trimester is when a lot of critical brain and nervous system development occurs. The second half of the trimester is a time of rapid body and limb growth. 

Here’s more on what to expect when you’re 13 weeks pregnant.

Baby at 13 weeks pregnant

Your baby is the size of a peach, 3 inches long and about 2 ounces. His/her head accounts for more than 50% of the crown to rump measurement, and that’s the way it’s going to be for a few more weeks. Starting now, your baby’s head growth is slowing down and fetal body growth is picking up. By about week 21, your baby’s body length will make up 2/3rds of your baby’s total crown to rump measurement. 

In organ development news, it’s the intestines time to shine. Your baby’s intestines, which were growing in the umbilical cord, are now making the trek to your baby’s abdomen and being drawn into the body. They’re joining the other organs, nerves, and muscles that are in their basic forms and starting to figure out how they work together. 

On your little’s sweet face, the eyes are moving closer together and the ears are also moving into place. Your baby now has a clearly defined neck and s/he’s holding the chin more upright. Hair has even sprouted on your little one’s scalp!

pregnancy week 13 embryo
Weekly development of a human fetus at 13 weeks pregnant.

As for your baby’s body, it’s moving. Your little’s muscular and nervous systems are developed enough for your baby to make jerky motions. While your baby’s legs are still on the short side proportionately, the arms are coming into their own and both the arms and legs are fully formed. Within those limbs, tissue is forming that will become bone. There’s a spinal cord already running the length of the vertebral canal in your baby’s back. Plus, tiny ribs are forming! And you’ll love this: your baby’s sex organs would be identifiable as boy/girl if seen outside of the womb.

Your body at 13 weeks pregnant

As pretty much everyone who’s ever had a baby will tell you, the second trimester of pregnancy is the ”easy” one. These are the weeks when pregnant women feel their best physically: no longer sick and not yet physically uncomfortable. You’re probably not as tired as you were, either, and might even be feeling energized and ready to take on your To Do list and get ready for baby.

Press gently on your abdomen about four inches below your belly button and you can probably feel the top of your uterus. It’s now filling your pelvis and expanding upwards. If you’ve had a baby before or if you’re on the slender side, you might be showing a bit. Even if no one else has noticed, you’re probably feeling like your regular clothes are becoming tighter. 

Expect your weight gain in the second trimester to be around a half pound a week. For some women, this is when reality begins to set in and they really feel pregnant. Other women see their small potbelly and changing body and feel fat. Remember that you’re not fat, your body is changing to grow and nurture a baby.

13 weeks pregnant ultrasound

Between 11-14 weeks, you might have an ultrasound scan to date your pregnancy and confirm your due date. Fetal measurements are most accurate during these weeks, when all babies measure the exact same crown-to-rump. In this ultrasound, you'll see that your baby at 13 weeks looks like a teeny, tiny baby. S/he’s literally just skin and bones because there’s no fat yet.

As part of this ultrasound, you also have the option of having the genetic screening known as a nuchal translucency (NT). This specialized ultrasound helps determine if your baby has Down syndrome or other chromosomal concerns like trisomy 18 or trisomy 13. In an NT, the technician measures a spot on the back of your baby’s neck called the nuchal fold, and uses that measurement to calculate the probability that your baby has a chromosomal abnormality. 

13 weeks is how many months pregnant? 

At this stage in your pregnancy, you're three months, one week (3m1w) pregnant.

Common symptoms at 13 weeks pregnant

  • Dizziness: Your body’s increased blood production means your blood pressure is lower. This might notice you feel dizzy or faint, especially in hot weather or during a hot shower which can cause your blood pressure to drop further. Something to be aware of, mama!
  • Stretch marks: With all the skin stretching that happens in pregnancy, stretch marks are inevitable for as many as nine out of 10 women. They can appear at any time during pregnancy, and are caused when the elastic fibers and collagen in the skin are pulled apart. The skin tears and the collagen breaks down and shows through as a pink, red, or purple indented streak. 
  • Round ligament pain: You could be experiencing some twinges and aches in your belly resulting from the stretching of the round ligament that tethers the uterus to the abdominal wall. It’s not harmful but it can be painful. 
  • Nose bleeds and/or bleeding gums: The extra blood in your body leads to swelling just about everywhere, including your gums and nasal passages.  
  • Congestion: Pregnancy rhinitis – stuffiness and nasal congestion as a result of your pregnancy – is a super common pregnancy symptom, and one that’s likely to stick around. Speak to your doctor before taking any over-the-counter medications for guidance on which are ok to take during pregnancy.
  • Blurred vision: Another seemingly random symptom of pregnancy is blurred vision, which you might have already begun experiencing, and may continue to experience until six weeks postpartum. It’s caused when the outer layer of your eye (the cornea) starts to thicken thanks to fluid retention.
  • Gas and Bloating: The pregnancy hormone progesterone slows digestion so your body can better absorb nutrients to nurture your growing baby, which is great, but it can also lead to gas, bloating, and constipation. Check out these tips for getting things moving and avoiding constipation in pregnancy

Pregnancy checklist at 13 weeks pregnant 

  • Share your news: Many women feel comfortable telling family and friends about their pregnancy since they've reached the second trimester. Now is also a good time to start thinking about a baby registry and researching the best baby gear, such as car seats and strollers.
  • Enjoy a treat: Hopefully, you’re feeling good and have seen an end to your morning sickness symptoms. Hooray if food is finally looking and smelling good again! 
  • Ditch the herbs: Love herbs and other natural remedies? As with any medicine, check with your doctor about their safety. Some natural remedies such as herbs can interfere with medications and some may even cause miscarriage.

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