Week 16
Your baby is the size of an avocado
What's happening this week
Your baby is now the size of an avocado — about 4.6 inches (120mm) from crown to rump and weighing roughly 3.5 ounces. This is one of the most popular size comparisons of pregnancy, and for good reason — it's the week when your baby starts to feel substantial.
Your baby's head is now upright and more proportional to the body. The eyes, though still closed, can detect changes in light — if you shone a bright light on your belly, your baby might turn away. The ears have nearly reached their final position on the sides of the head, and the inner ear structures are continuing to mature.
Limb movements are becoming increasingly coordinated. Your baby can flex their arms and legs, make fists, and even grab the umbilical cord (a favorite pastime in utero). These movements are visible on ultrasound, but most people still can't feel them yet — the baby is still small enough that their kicks don't reach the uterine wall with enough force to register. Some experienced moms may begin to feel the very first flutters of movement this week, often described as 'bubbles' or 'popcorn popping' — but first-time parents usually don't feel movement until weeks 18-22.
Your baby's skin is becoming thicker, though it's still translucent. The musculoskeletal system is strengthening, and your baby's movements are becoming more purposeful rather than reflexive. The circulatory system is fully functional, pumping about 25 quarts of blood per day — a number that will increase to 300 quarts by the end of pregnancy.
The nervous system is also making important connections, allowing your baby to make more complex movements and respond to stimuli.
Your body this week
You're four months pregnant, and for many people this is when the pregnancy starts to feel fun rather than merely survivable. The nausea is likely gone, energy has returned, and your bump is growing into something you're actually proud to show off.
Some exciting physical changes this week: your breasts may start producing colostrum, the thick yellowish premilk that provides essential antibodies to your newborn. You might not notice it — some people don't produce visible colostrum until the third trimester — but the preparation is happening.
You may experience some new sensations: a fluttering or bubbling feeling in your lower abdomen that might be gas, or might be the very first fetal movements (called quickening). First-time parents often can't distinguish between the two at this stage, and that's perfectly normal. If you don't feel anything yet, there's absolutely nothing wrong — most first-time parents feel movement between weeks 18 and 22.
Your next prenatal visit will likely include a discussion about the anatomy scan, which happens around week 20. This detailed ultrasound examines your baby's organs, limbs, spine, and brain — and, if you want to know, can determine the sex with high accuracy.
You may notice that your balance feels slightly off. Your center of gravity is shifting as your uterus grows, which can make you feel less steady on your feet. Wear flat, stable shoes and be mindful of uneven surfaces.
If you're feeling well, consider planning a babymoon — a pre-baby getaway with your partner. The second trimester is generally the most comfortable time to travel.
For dads
Week 16 is a milestone that often flies under the radar: your baby is now the size of an avocado, which for some reason is the comparison that makes it click for many dads. The baby is moving, growing, and becoming more of a tiny person every day. If your partner is starting to feel flutters of movement, she may grab your hand to try to share the experience — though it'll likely be a few more weeks before you can feel anything from the outside. Practically, start thinking about the anatomy scan at week 20. This is the appointment where you'll get a detailed look at your baby — including, potentially, finding out the sex. Decide in advance whether you want to know, and plan to be at this appointment. It's one of the most memorable ultrasounds of the pregnancy.
Consider planning a babymoon — a trip with your partner before the baby arrives. The second trimester is the ideal travel window: she's feeling good, the belly isn't too large for comfortable travel, and you both could use some quality time together before life changes forever. It doesn't have to be extravagant — even a long weekend away counts. The point is intentional time together as a couple, because once the baby arrives, couple time becomes much harder to find.
Common concerns
Is it normal to feel movement at 16 weeks, or is it too early?+
Some people — especially those who've been pregnant before — can feel movement as early as 16 weeks. It's often described as flutters, bubbles, or a popcorn-popping sensation. First-time parents usually don't feel movement until weeks 18-22 because they're less familiar with the sensation. If you're not feeling anything yet, that's completely normal. The timing depends on factors like placenta position, body type, and whether this is your first pregnancy.
What happens at the anatomy scan?+
The anatomy scan is a detailed ultrasound usually performed around week 20. The technician examines your baby's brain, spine, heart, kidneys, limbs, face, and other structures to check for normal development. They also assess the placenta location, amniotic fluid levels, and may determine the baby's sex. The scan typically takes 30-60 minutes. If anything looks unusual, your provider will discuss next steps — but for the vast majority of pregnancies, the anatomy scan is reassuring.
Is it safe to travel during the second trimester?+
For most uncomplicated pregnancies, the second trimester is the safest and most comfortable time to travel. Most airlines allow pregnant travelers to fly up to 36 weeks for domestic flights (32 weeks for international). Stay hydrated, walk around regularly on flights to prevent blood clots, and carry your prenatal records. Check with your provider before planning travel if you have any complications or risk factors.
When should I worry about swelling during pregnancy?+
Mild swelling in the feet and ankles is common during pregnancy, especially later in the day, and is usually harmless. However, contact your provider if swelling is sudden, severe, affects your face or hands, or is accompanied by headache, vision changes, or upper abdominal pain. These can be signs of preeclampsia, a condition that requires medical attention. Staying hydrated, elevating your feet, and wearing supportive shoes can all help manage normal pregnancy swelling.
Product picks for week 16
We may earn a small commission if you purchase through links on this page — at no extra cost to you. Learn more.
Babymoon travel essentials kit
Second trimester is prime travel time — a kit with compression socks, neck pillow, and healthy snacks makes the trip comfortable.
Pregnancy-safe body moisturizer
Your skin is stretching and may feel tight or itchy — a rich, fragrance-free moisturizer keeps skin hydrated and comfortable.
Baby registry starter guide
It's not too early to start thinking about what you'll need — a guide helps you sort essentials from nice-to-haves before the registry overwhelm hits.
A quick note: This content is for informational purposes only and is not a substitute for professional medical advice. Always talk to your healthcare provider about any questions or concerns. Learn how we create our content.
Content based on guidance from the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), Mayo Clinic, and peer-reviewed medical literature. Learn more about how we create our content.