At 15 weeks pregnant, you’re about three and a half months into your pregnancy and just entering the second trimester. You have roughly 25 weeks, or a little under six months, left until your due date. If you’ve been counting weeks and wondering where that puts you on the calendar, you’re not alone. Pregnancy math is genuinely confusing because months and weeks don’t divide evenly.
Weeks, Months, and Trimester at 15 Weeks
A full-term pregnancy lasts about 40 weeks, which works out to roughly nine calendar months (or ten lunar months of four weeks each). Because most months have 30 or 31 days rather than a neat 28, the week-to-month conversion never lines up perfectly. At 15 weeks, you’re working your way through your third month and crossing into your fourth. The second trimester spans weeks 14 through 28, so you’ve just entered it.
This trimester is often called the “honeymoon phase” of pregnancy for a reason. Many of the first-trimester symptoms like nausea and extreme fatigue start to fade, and you likely have more energy than you did a few weeks ago. You still have about 175 days to go.
How Big Your Baby Is at 15 Weeks
Your baby is about the size of an apple, measuring roughly 6.5 inches from head to heel and weighing just over 4 ounces. That’s a significant jump from just a few weeks earlier, when your baby was closer to the size of a lime. Growth accelerates noticeably during the second trimester.
Bone development is a major milestone at this stage. The skeleton is hardening enough that bones will soon be visible on ultrasound images. Your baby’s scalp hair pattern is also forming right now, laying the groundwork for whatever head of hair (or lack of it) they’ll be born with. The baby is growing quickly, and by 15 weeks after your last period, the actual time since conception is about 13 weeks.
What You Might Be Feeling
One of the most common new symptoms around 15 weeks is round ligament pain. Two rope-like bands of tissue, each about 4 to 5 inches long, connect your uterus to your lower abdominal wall through your groin. As your uterus grows, these ligaments stretch and pull, which can cause sharp, stabbing sensations in your abdomen, hips, or groin, especially when you move suddenly, sneeze, or change positions quickly.
Women often describe it as aching, cramping, or a pulling sensation on one or both sides. It typically shows up in the second trimester, right around now, and for some people it eases by the third trimester. For others, it lingers until after delivery. Rest and gentle movement help, along with avoiding sudden position changes. A warm (not hot) bath can ease the discomfort, and staying off your feet for long stretches reduces the strain. Avoiding heavy lifting also makes a difference.
You may also notice your pants fitting tighter even if you’re not obviously “showing” yet. Some women start to feel tiny flutters of movement around this time, though it’s more common to notice those a few weeks later, especially in a first pregnancy. Nasal congestion is another surprisingly common second-trimester symptom, caused by increased blood flow to your mucous membranes.
Nutrition and Weight Gain
Now that you’re in the second trimester, your calorie needs increase, but not by as much as you might expect. The American College of Obstetricians and Gynecologists recommends an extra 340 calories per day during the second trimester. That’s roughly a large banana with a couple tablespoons of peanut butter, not the “eating for two” free-for-all that the old saying suggests.
If first-trimester nausea kept you from eating well, this is a good time to focus on nutrient-dense foods. Iron, calcium, and protein demands all rise in the second trimester as your baby’s bones develop and blood volume increases.
Screening Tests Around 15 Weeks
Week 15 is the earliest point in the window for the quadruple screen, a blood test that checks for markers associated with certain chromosomal conditions and neural tube differences. The test can be done between weeks 15 and 22, but it’s most accurate between weeks 16 and 18. If your provider hasn’t already discussed this with you, it will likely come up at your next appointment. The test is a simple blood draw, and results typically come back within a week or two.
If you had first-trimester screening (like a nuchal translucency ultrasound or cell-free DNA test), your provider may use those results alongside the quad screen or may skip it entirely depending on your situation.
Counting Down From Here
At 15 weeks, you’re 37.5% of the way through a typical 40-week pregnancy. The second trimester runs through week 28, giving you another 13 weeks before entering the third trimester. Most women find this middle stretch the most comfortable, with more energy and fewer disruptive symptoms than either end of pregnancy. It’s a good window for travel, exercise, and preparing your space for the baby, since the third trimester brings its own set of physical limitations.