18 Weeks Pregnant: Exciting Changes in Your Baby's Senses!

Now that you’re 18 weeks pregnant, your baby’s hearing is developing, and they can finally start to hear sounds from inside your body. This milestone marks an exciting point in your fifth month. You might also be feeling your belly grow heavier or noticing those tiny flutters of movement.  

Here’s a closer look at how your baby’s growing and what pregnancy symptoms to expect at this stage. 

Your Baby’s Development at 18 Weeks 

When you’re 18 weeks pregnant, your baby’s size is about 14 cm (5.5 in) long from crown to rump and weighs around 200 g (7 oz), according to the Mayo Clinic. But the most exciting development is happening with their senses! 

Your baby’s hearing is developing! 

Your baby's hearing is beginning to develop at this time, notes the American Academy of Pediatrics (AAP). They may even be able to hear the first sounds from inside your body, like your heartbeat. However, they can't quite hear your singing or reading from outside the belly just yet (expect that to start around Week 27 to Week 29)!

They're practicing for the outside world. 

The part of the brain that controls motor movements is now fully formed, according to the American College of Obstetricians and Gynecologists (ACOG). This allows your baby to practice yawning, hiccupping, and making facial expressions.  

You might even feel those hiccups as tiny, rhythmic taps—sensations you may have first noticed in Week 17.

Your baby is covered in a fuzzy layer. 

This week, your baby's skin is covered in lanugo, which is a very fine, fuzz-like hair. This downy layer helps keep your baby warm in the womb, notes the Cleveland Clinic. 

Your baby’s movements are getting stronger. 

When you’re 18 weeks pregnant, your baby’s movements become strong. If this is your first pregnancy, you may start to feel these movements, known as quickening. If you’ve been pregnant before, you probably would have felt them earlier. (See Week 16 for more on quickening.) 

Your Symptoms and Body Changes 

Your bump may be very visible now, especially if this isn’t your first pregnancy. Here are the common symptoms at this stage. 

You might feel dizzy. 

Feeling lightheaded is a common symptom during the second trimester. Your pregnancy affects your cardiovascular system, which can sometimes lead to low blood pressure, explains the American Pregnancy Association. To help manage dizziness, stand up slowly when you're moving from a sitting or lying position. 

You may start seeing stretch marks. 

As your bump grows, you might begin to see stretch marks, reddish-purple lines on your belly or hips. A 2024 review on pregnancy skin changes found that these affect up to 90% of women and are due to skin stretching, hormones, and genetics.  

There’s no proven way to prevent them but staying hydrated and moisturizing can help reduce their appearance. They’ll naturally fade to a lighter, silvery color over time. 

You may notice more body aches and heaviness. 

Now that you’re 18 weeks pregnant, body aches are typical. You might have backaches or sharp, quick pains in your lower belly. This happens because your growing uterus is shifting your center of gravity, and pregnancy hormones are relaxing your ligaments. (See Week 13 for more information on backaches and round ligament pain.) 

You might be dealing with constipation. 

Feeling backed up? As your uterus grows, it puts pressure on your bowels, while pregnancy hormones slow down your digestion. You can relieve constipation by eating more fiber-rich foods. 

What to Expect at the Anatomy Scan 

You're now in the window for the mid-pregnancy ultrasound (a.k.a. the anatomy scan), which usually happens between 18 and 22 weeks. This detailed scan checks your baby's health and development from head to toe. 

You can also choose to learn about your baby’s gender at this time. Studies on second-trimester ultrasounds have found them to be highly accurate in determining gender, which you can read about in your guide to Week 19. 

What to Eat This Week 

As you eat for two, continue to focus on quality over quantity by prioritizing key nutrients like iron, calcium, omega-3s, and fiber. As always, stay hydrated to help with digestion and circulation. 

The energy and nutrients you consume help to support your baby, the placenta, and your increased blood volume. This week, you might have gained around 4 to 6 kg (10 to 14 lbs.), but this varies for every person. 

Your doctor will track your weight to make sure it's in a healthy range for you. (Learn more about weight gain in Week 17.) 

Self-Care Guide for Week 18 

This is an exciting time! Use these quick tips to help you feel your best as you head toward the halfway mark.

• Get ready for your big scan. List any questions or concerns you may have and decide if you want to know the gender.
• Keep moving gently. Ask your doctor about safe and light exercises that can help ease backaches and boost your mood.
• Sleep on your side. Start looking for a body pillow that you can use to support your belly and back as you get used to sleeping on your left side.
• Get plenty of extra rest, as you'll likely feel more tired, especially if you're 18 weeks pregnant with twins. 

When to Call Your Doctor 

Be sure to check in with your ob-gyn if you experience: 

• Persistent or severe pain, especially in your back or belly
• Any vaginal bleeding or spotting at 18 weeks pregnant
• A sudden gush or constant leak of fluid from your vagina
• Feeling very dizzy, not just a little lightheaded
• A fever or chills 

You’re Almost Halfway There! 

There’s a lot to look forward to when you’re 18 weeks pregnant. You might be feeling your baby move for the first time, your bump is growing, and you may soon find out your baby’s gender. Enjoy this exciting time and take care of yourself as you prepare for all the changes ahead.  

Looking to connect with like-minded parents? Join the ParentTeam Moms and Dads Facebook group and share what it’s like being 18 weeks pregnant.