Pregnancy › Week by Week › Week 13
At 13 weeks your baby is about the size of a lemon. This is the final week of the first trimester, and fingerprints, vocal cords, and more coordinated movement are all coming along.
Size
A lemon
crown to rump
Length
2.9 in
about 7.4 cm
Weight
0.81 oz
about 23 g
Your baby at 13 weeks
Fingerprints are forming, vocal cords are developing, and movement is getting more coordinated.
Your baby has grown a great deal in a short time and is looking more proportioned, with the body catching up to that large early head. This is the last week of the first trimester, and the fine detail work is well underway.
Hands and voice. Tiny, unique fingerprints are forming on those little fingertips, and the vocal cords are developing, laying the groundwork for the very first cry months from now.
Inside. The intestines, which spent the early weeks growing inside the umbilical cord, have moved into the abdomen where they belong. The kidneys are making urine, and the digestive system keeps maturing.
Movement. Your baby’s movements are becoming smoother and more coordinated, with stretching, curling, and even thumb finding on the way. You still will not feel it for a while yet, but the practice is happening every day.
How big is your baby at 13 weeks?
About 2.9 inches (7.4 cm) crown to rump and around 0.81 ounces (23 g).
Measurements this early are taken crown to rump, from the top of the head to the bottom, because the legs are usually curled up. Your baby has roughly tripled in length since the start of the first trimester.
Your body at 13 weeks
Many people feel the nausea lift and energy return this week, and the miscarriage risk drops noticeably after the first trimester.
Reaching the end of the first trimester is a real milestone. For many people this is when the fog begins to lift: nausea eases, appetite returns, and that bone deep tiredness starts to loosen as the placenta takes over hormone production. It does not happen for everyone on the same schedule, but if you have been counting down, this is often where relief begins.
It is also worth knowing that the chance of miscarriage drops noticeably once you are past the first trimester, which is part of why many people feel ready to share their news around now. You may notice a small bump starting to show, especially if this is not your first pregnancy, and your uterus is rising up out of your pelvis, which some people feel as stretching sensations low in your belly. Enjoy the returning energy while it lasts.
What is normal, and when to call your provider
Mild cramping and light spotting can be normal in early pregnancy, but call your doctor or midwife the same day if you have any of these:
- Heavy bleeding, especially soaking a pad, or passing clots
- Severe or persistent abdominal or pelvic pain, or strong one sided pain
- A fever over 100.4°F (38°C)
- Severe vomiting where you cannot keep any fluids down, which can be more than ordinary morning sickness and is worth treating
- Fainting, or dizziness that does not pass
Your week 13 checklist
- Have your NT scan if you have not yet; the window closes around 14 weeks
- Keep taking your prenatal vitamin with folate every day
- Use any returning energy for gentle movement you enjoy, a daily walk counts
- Think about how and when you would like to share your news
- Start reading up on what the second trimester has in store
Appointments and tests around 13 weeks
If you want the NT scan and have not had it, this is close to the end of the window.
The nuchal translucency (NT) scan window runs from 11 to 14 weeks, so if you would like this screening and have not had it yet, week 13 is the time to book it before the window closes. Combined with a first trimester blood test, it estimates the chance of certain chromosomal conditions. Remember that it is a screen, not a diagnosis, and it is optional. If you have already had your screening, or chosen to skip it, the rest of your care around now is likely routine: checking in with your provider, monitoring your health, and looking ahead to the anatomy scan in the second trimester. There are no wrong choices here.
A few things worth having on hand now
A note for your partner
The end of the first trimester can bring a wave of relief for both of you. If you have been holding your breath, this is a nice moment to celebrate in whatever small way feels right. It is also a good time to plan any news you want to share together, so you are on the same page about who hears what and when.
You are not alone this week
Thirteen weeks marks the close of a chapter that can feel very long. If the nausea is finally easing, savor it, and if it is taking its time, hang in there, because relief is often just ahead. However you arrive at this point, reaching the end of the first trimester is genuinely worth marking.
13 weeks pregnant, common questions
Is 13 weeks the second trimester?
It is right on the line. Week 13 is usually counted as the last week of the first trimester, with the second trimester beginning around week 14. Either way, you are at the doorstep of a new phase.
Does the miscarriage risk really drop now?
Yes. The chance of miscarriage falls noticeably once you are past the first trimester. That reassurance is part of why many people feel ready to share their news around this time.
Will my energy come back this week?
For many people it starts to. As the placenta takes over hormone production, nausea often eases and energy returns around 13 to 14 weeks. It does not happen for everyone on the same schedule, so be patient if you are not there yet.
Is it too late for the NT scan?
Not yet, but close. The NT scan window runs from 11 to 14 weeks, so if you want it and have not had it, book it soon. After the window closes, other screening options are still available; ask your provider.
Sources
- American College of Obstetricians and Gynecologists (ACOG), first trimester care and screening guidance.
- Mayo Clinic, Fetal development: the 1st trimester.
- MedlinePlus, National Library of Medicine (NIH), Fetal development and prenatal care.
Medical disclaimer: This page is for information and education only and is not a substitute for professional medical advice. Every pregnancy is different. Always follow the guidance of your doctor, midwife, or qualified provider, and contact them with any concerns.