GUIDE
Your baby's skeleton is hardening from cartilage to bone, and a protective layer of fat is starting to form.
At the size of a pomegranate, your baby is building the body fat that will help regulate temperature after birth.
Be prepared from day one
Your baby is about the size of a pomegranate — roughly 5 inches long from crown to rump and weighing around 5 ounces. They are starting to fill out as a layer of body fat begins to develop beneath the skin.
This fat, called brown fat, will eventually play a crucial role in regulating your baby's body temperature after birth. Right now it is just beginning to accumulate, and your baby still looks quite thin and translucent — but that is changing week by week.
The skeleton is going through a major transformation. What was once soft, flexible cartilage is gradually hardening into bone through a process called ossification. You can actually see this change on ultrasound — the bones appear as bright white lines. Despite the hardening, the skeleton will remain somewhat flexible, which is important for navigating the birth canal when the time comes.
Your baby's sweat glands are forming, and their fingerprints are becoming unique — the patterns are set now and will remain the same for life. The umbilical cord is growing thicker and stronger, keeping up with your baby's increasing nutritional demands. Since last week, the hearing system continues to mature as well.
If round ligament pain has not visited you yet, there is a good chance it shows up around now. As your uterus expands, the ligaments that anchor it to your pelvis are being stretched like rubber bands. Quick movements — sneezing, coughing, standing up too fast, or rolling over in bed — can cause a sharp, sudden pain on one or both sides of your lower abdomen. It is startling but harmless. You can read more in our round ligament pain guide.
Your center of gravity is shifting as your belly grows, and you might notice that your balance feels slightly off. This is a normal adjustment that will continue throughout pregnancy. Be mindful on stairs and uneven surfaces, and consider swapping heels for flats if you have not already.
Many women experience vivid, sometimes bizarre dreams during the second trimester. This is likely caused by a combination of hormonal changes, disrupted sleep cycles, and the emotional processing that comes with becoming a parent. They are harmless, even if they are occasionally unsettling. You may also notice stretch marks starting to appear on your belly, breasts, or hips as your skin stretches to keep up with your growing baby.
Increased vaginal discharge is also normal at this point. Called leukorrhea, it should be thin, white or clear, and mild-smelling. It is your body's way of keeping the birth canal clean and preventing infection. If it changes color, develops a strong odor, or is accompanied by itching, let your provider know.
Every pregnancy is different. These are among the most commonly reported symptoms this week, but your experience may vary.
This is a good week to address some of the physical discomforts that come with a growing belly, and to start thinking ahead. Focusing on nutrient-dense foods can help fuel the rapid growth happening right now.
Move slowly when changing positions — especially getting out of bed or standing up from a chair. A warm (not hot) bath or a maternity support belt can help. If you feel a sneeze coming, try bending your hips slightly to reduce the pull on the ligaments.
Stretch marks are largely genetic, but keeping your skin well-hydrated can help with the itching that comes with stretching skin. Cocoa butter, coconut oil, or a fragrance-free lotion applied daily can provide relief.
Make sure your prenatal includes adequate iron, as your blood volume is increasing rapidly. Iron deficiency anemia is common in pregnancy and can leave you feeling exhausted. If your current vitamin causes nausea, ask your provider about switching brands.
The second trimester is a good time to start thinking about the financial side of a new baby — insurance coverage, parental leave, and a rough idea of what you will need to buy versus what you can borrow or receive as gifts.
When in doubt, call your provider. Round ligament pain is common, but persistent or severe abdominal pain should always be evaluated.
At 18 weeks, your baby will be the size of a sweet potato and you may feel movement more clearly. Your baby is yawning and hiccupping in there, and if you are carrying a girl, her uterus and fallopian tubes are now fully formed.
The anatomy scan is just around the corner — one of the most exciting appointments of your pregnancy.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
