TL;DR
- Your baby is the size of a lemon, about 7.4cm
- Fingerprints are forming on those tiny fingers — completely unique to your baby
- You're entering the second trimester, and energy may start to return
- Your energy may return as you enter the second trimester
Your Baby This Week
At thirteen weeks, your baby measures about 7.4cm — roughly the size of a lemon — and is developing something that will be theirs and only theirs for life: fingerprints.
The ridges and swirls that form fingerprints are taking shape on your baby's fingertips this week. These patterns are determined by a combination of genetics and the unique environment in the womb — the pressure of amniotic fluid, the way your baby touches the uterine wall, and random variations in growth. Even identical twins have different fingerprints. Your baby is literally becoming one of a kind.
Your baby's body proportions are starting to look more balanced. The head, while still the largest body part, is now about one-third of the total body length instead of half. The body and limbs are growing rapidly, and your baby is looking more and more like the newborn you'll eventually meet.
The vocal cords are forming in the larynx, though your baby won't use them until that first cry after birth. The intestines are producing meconium — the dark, tar-like substance that will be your baby's first bowel movement after delivery. The bones of the skeleton are continuing to harden, and the ribs are visible on ultrasound.
Your baby is incredibly active right now. They're stretching, kicking, turning, and even practicing breathing movements by inhaling and exhaling amniotic fluid. The movements are building muscle strength and coordination, even though you won't feel them for another several weeks.
Your Body This Week
Welcome to the gateway of the second trimester. For many people, week 13 marks a real turning point. The crushing fatigue of the first twelve weeks may begin to lift. Morning sickness, while not always gone completely, often decreases significantly. You might wake up one morning and realize you actually feel... good. Maybe even energetic.
This shift happens because hCG levels are decreasing from their first-trimester peak, and the placenta has fully taken over hormone production. Your body has adjusted to its new normal, and the intense adaptation period of the first trimester is winding down.
Your bump may be making its debut. The uterus is now clearly above the pelvic bone, and many people start to show around this time. If this is your first pregnancy, you might not have an obvious bump yet — but you'll likely notice your clothes fitting differently. If you've been pregnant before, you might already look noticeably pregnant.
Your appetite may come roaring back after weeks of food aversions and nausea. You might find yourself suddenly hungry in a way you haven't been since before pregnancy. This is normal and healthy — your baby is growing rapidly and your body needs fuel. Try to channel this renewed appetite toward nutrient-rich foods while still enjoying the things you're craving.
Some people notice changes in their libido around this time. The combination of reduced nausea, increased energy, and heightened blood flow can lead to an increase in desire. Others still feel too uncomfortable or tired. Both are normal. Intimacy during a healthy pregnancy is safe unless your provider has told you otherwise.
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Common Questions at Week 13
Is the second trimester really easier?
For many people, yes. The second trimester (weeks 14-27) is often called the "golden period" of pregnancy. Morning sickness typically improves, energy returns, and you haven't yet reached the physical discomfort of the third trimester. Of course, every pregnancy is different — some people feel great, and others continue to deal with symptoms. But statistically, the second trimester tends to be the most comfortable phase.
When will I feel the baby move?
Most first-time parents feel the first fetal movements, called quickening, between weeks 18 and 22. It often starts as a subtle fluttering or bubbling sensation that's easy to dismiss as gas. If you've been pregnant before, you might recognize the movements earlier — sometimes as early as week 16. The timing varies, and it doesn't indicate anything about your baby's health.
Should I be gaining weight now?
Most people gain between 1 and 5 pounds during the entire first trimester. In the second trimester, a general guideline is about 1 pound per week, though this varies based on your starting weight and your provider's recommendations. Focus on eating a balanced diet and let your provider track your weight at each visit. Weight gain during pregnancy isn't linear — it comes in spurts and plateaus.
Is it safe to travel during the second trimester?
The second trimester is generally considered the best time for travel during pregnancy. You're past the highest-risk period, morning sickness has usually improved, and you're not yet large enough to be physically uncomfortable during long trips. Stay hydrated, stretch your legs during long drives or flights, and check with your provider if you have any complications.
When is the anatomy scan?
The anatomy scan (also called the mid-pregnancy ultrasound or level 2 ultrasound) is typically performed between weeks 18 and 22. This detailed ultrasound examines your baby's organs, bones, brain, heart, and overall growth. It's also the appointment where many parents learn the sex of their baby, if they choose to find out.
This Week's Tip
Your energy may return as you enter the second trimester. After weeks of feeling like you could sleep at your desk, this renewed energy can feel amazing — like someone flipped a switch. Use this energy thoughtfully. It's a great time to tackle things you've been putting off: scheduling appointments, organizing your space, exercising, or starting to research baby gear. But don't feel like you need to do everything at once. The second trimester is a gift of relative calm between the intensity of the first and third trimesters. Enjoy it. Move your body, eat foods that nourish you, and take advantage of feeling more like yourself again. You've earned this reprieve.
Sources
- American College of Obstetricians and Gynecologists (ACOG). How Your Fetus Grows During Pregnancy.
- Mayo Clinic. Fetal Development: The 1st Trimester.
