At 15 weeks pregnant you are about 3 1/2 months along, in the second trimester, with about 25 weeks to go until your estimated due date.
At 15 weeks pregnant many people start to feel more like themselves: Mayo Clinic says the worst of the nausea often is gone in the second trimester. Meanwhile your baby is growing fast, and the window for second trimester screening opens this week.
This guide covers development, size, symptoms, your belly, tests, sleep and when to call. Every clinical detail was read in October 2026 on the primary sources named in the text, and where sources disagree, we print both.
Key Takeaways
15 weeks pregnant is about 3 1/2 months, or 13 weeks after conception (Mayo Clinic), with about 25 weeks to go.
Mayo Clinic puts the baby at almost 3 1/2 inches crown to rump at week 14 and about 4 3/4 inches and 4 ounces at week 16.
Many people have more energy now; a stuffy nose, bleeding gums, round ligament pain and heartburn are common.
The optional quad screen runs from week 15 to 22, and amniocentesis, an optional diagnostic test, is usually done from week 15 to 20.
Call right away for bleeding, severe belly pain, a fever above 100.4 F, a severe headache or a swollen, red leg.
Table of Contents
15 Weeks Pregnant at a Glance
Quick Answer
At 15 weeks pregnant you are about 3 1/2 months along, in your 4th month, with about 25 weeks to go. You are in the second trimester by every definition we checked. Mayo Clinic says your baby is growing quickly and bones may now show on ultrasound, and the window for the optional quad screen opens this week (UPMC, MedlinePlus).
15 weeks pregnant
What to know
Trimester
Second. UPMC, using the American College of Obstetricians and Gynecologists (ACOG) definition, says it runs from 14 weeks, 0 days until after 27 weeks, 6 days. MedlinePlus counts week 14 through week 28.
Month
About 3 1/2 months, so your 4th month, counting 4 weeks and a few days per month. Months are a convention, not a medical unit.
Weeks to go
About 25 (40 minus 15, counted from the first day of your last menstrual period).
Baby’s size
Between Mayo Clinic’s week 14 figure (almost 3 1/2 inches crown to rump, about 1 1/2 ounces) and its week 16 figure (about 4 3/4 inches, about 4 ounces).
Common symptoms
More energy for many, a stuffy nose or nosebleeds, bleeding gums, round ligament pain, heartburn.
This week’s care focus
Deciding about second trimester screening (the quad screen runs from week 15 to 22).
15 weeks pregnant: quick facts with sources.
How the weeks are counted. Cleveland Clinic explains that pregnancy is dated from the first day of your last menstrual period (LMP), about two weeks ahead of conception, which is why Mayo Clinic calls week 15 13 weeks after conception. If an early ultrasound changed your due date, use the adjusted dates.
15 weeks pregnant in months. Cleveland Clinic’s guide, which uses four-week months, places weeks 13 through 16 in month 4.
Your Baby’s Development at 15 Weeks
Source and timing
What it says is happening
Mayo Clinic, week 15
The baby is growing quickly and bone development continues. Bones may become visible on ultrasound. The scalp hair pattern is forming.
Cleveland Clinic, week 15
Some organs, like the intestines and ears, are moving to their permanent places. The fetus practices breathing with amniotic fluid as the lungs begin to develop, and makes more purposeful movements, like sucking a thumb.
Cleveland Clinic, week 14
The skin starts to thicken and fine hair begins to grow. The external genitals are fully developed, and fingerprints begin to form.
Mayo Clinic, week 16
The head is upright and the eyes can move slowly. Arm and leg movements can be seen on ultrasound, but they are likely too small to feel.
Cleveland Clinic, week 16
The ears are developed enough to hear you talk.
Fetal development around week 15, by source.
Can you feel the baby move at 15 weeks? Probably not yet, and that is expected. UPMC says most people start to feel movement around 20 weeks, some as early as 16 weeks. Cleveland Clinic calls the first movements quickening, says they can feel like a flutter, and says most people begin to feel kicks around week 19.
How Big Is Your Baby at 15 Weeks?
None of the primary sources we read gives a measurement for week 15 itself, so here are the nearest figures on each side, exactly as each source states them. A baby at 15 weeks sits between the week 14 and week 16 rows.
Source
Week
Length
Weight
Mayo Clinic
14
Almost 3 1/2 inches (87 mm), crown to rump
About 1 1/2 ounces (45 g)
UPMC
Start of second trimester
“About the size of a peach”
Not given
Mayo Clinic
16
About 4 3/4 inches (120 mm), crown to rump
About 4 ounces (110 g)
Cleveland Clinic
16 (end of month 4)
About 5 inches, “about as big as an avocado”
About 4 ounces
Baby size near 15 weeks. Sources differ, so each is printed.
Mayo Clinic measures crown to rump (head to tailbone), leaving out the legs. Cleveland Clinic does not say how it measured. These are typical figures, not targets.
A 15 week ultrasound? A routine scan is not usually due this week. MedlinePlus says the anatomy ultrasound is done around 20 weeks. Mayo Clinic says the sex likely becomes clearer around week 14, but no source we read promises it can be seen at 15 weeks.
15 Weeks Pregnant Symptoms
Mayo Clinic says that in the second trimester the worst of the nausea often is gone, and you may feel less tired and have more energy. That is common, not guaranteed: if nausea is not easing, tell your provider.
Symptom
What the sources say
What may help
Stuffy nose and nosebleeds
Pregnancy can make the inside of your nose swell and bleed easily (Mayo Clinic).
Saline drops or rinses, a humidifier, fluids and a little petroleum jelly around the nostrils (Mayo Clinic).
Bleeding gums
Brushing and flossing can make your gums bleed (Mayo Clinic).
Rinse with salt water, use a softer toothbrush and keep brushing and flossing (Mayo Clinic).
Round ligament pain
Usually occurs in the second trimester, weeks 14 through 27. An ache, cramp, or sharp, stabbing or pulling feeling, usually with sudden movement, lasting seconds to minutes (Cleveland Clinic).
Rest, gentle stretching, a belly band, a warm (not hot) bath, and holding your belly or flexing your hips when you sneeze, cough or laugh (Cleveland Clinic).
Heartburn
The growing uterus presses on the stomach and hormones relax the esophagus muscles (UPMC). Often worse at night (MedlinePlus).
No big meal within a few hours of bedtime (MedlinePlus).
Dizziness
Changes in blood flow might leave you dizzy (Mayo Clinic).
Fluids and slow position changes. If dizzy, lie down on your side (Mayo Clinic).
Common symptoms at 15 weeks pregnant.
Other changes. Mayo Clinic says urinary tract infections are common in pregnancy: call about burning, urgency, cloudy urine, fever or backache, or about discharge with a strong smell or odd color.
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Your 15 weeks pregnant belly. Mayo Clinic says your belly grows as your uterus makes room for the baby, and UPMC lists a visible baby bump among second trimester changes. None of our sources names a week by which you should be showing, so a small bump or no obvious bump at 15 weeks tells you little on its own. Our pregnant belly by month guide shows the usual progression.
Breasts: Mayo Clinic suggests a bra with wide straps or a supportive sports bra as they grow.
Hips and back: UPMC says ligaments stretch to widen the pelvis, which can cause hip and back pain.
Braxton Hicks: Mayo Clinic describes a slight tightness that comes and goes, and says to call if tightenings become regular and keep getting stronger.
Appetite: UPMC says you need about 340 more calories a day in the second trimester.
Prenatal Care, Tests and Appointments Around Week 15
UPMC says second trimester visits are usually every four weeks. MedlinePlus says your provider will weigh you, measure your abdomen, check your blood pressure and make sure certain vaccinations are given.
Test
Window
What it is
Source
Quad screen (optional)
Weeks 15 to 22; most accurate at weeks 16 to 18 (MedlinePlus)
A screening blood test. It does not diagnose: it helps decide whether more testing is needed
UPMC, MedlinePlus
Amniocentesis (optional)
Usually weeks 15 to 20 (UPMC, MedlinePlus lab tests page); weeks 14 to 20 on MedlinePlus’s prenatal care page
A diagnostic test of a small sample of amniotic fluid
UPMC, MedlinePlus
Anatomy ultrasound
Around 20 weeks (coming up)
Checks the baby’s organs, size and movement, the placenta and fluid; about 45 minutes
MedlinePlus, UPMC
Tests around 15 weeks, as read in October 2026.
Screening versus diagnosis. MedlinePlus explains that screening tests have no risks but do not diagnose problems; they show whether a baby might have one. A result suggesting a higher chance may lead to a diagnostic test such as amniocentesis. The choice is yours.
About amniocentesis. MedlinePlus says it diagnoses certain conditions, such as Down syndrome, some genetic disorders and neural tube defects, and that having it is your choice. It says serious complications are extremely rare, with a very slight risk (less than 1 percent) of miscarriage.
Learning the sex. MedlinePlus says the ultrasound around 20 weeks can determine the sex if you want to know. Planning to share it? See our gender reveal ideas.
What to Do This Week: A Simple Checklist
Decide about the quad screen: the window opens now and accuracy is best at weeks 16 to 18 (MedlinePlus).
Ask when your anatomy scan will be, and decide whether you want to learn the sex.
Switch to a softer toothbrush and keep flossing (Mayo Clinic).
Get a supportive bra and wear sunscreen outdoors (Mayo Clinic).
Walk or swim most days if your provider agrees (UPMC).
Save your provider’s daytime and after-hours numbers in your phone.
Sleep at 15 Weeks Pregnant
MedlinePlus says you may sleep well in the first trimester and that sleep can get harder later in pregnancy, without describing the second trimester separately. Its reasons include bathroom trips, heartburn that is often worse at night and aches.
Sleep position. MedlinePlus’s general advice for pregnancy, not tied to a particular week, is that sleeping on your side with knees bent is likely the most comfortable, and keeps the baby from pressing on the large vein that returns blood from your legs to your heart. It says many providers recommend the left side, the right side is fine if your left hip gets sore, and sleeping flat on your back is not recommended. Ask your provider what they suggest.
Keep a schedule: same bedtime and wake time each day (MedlinePlus).
Watch the evening: limit caffeine and skip big meals right before bed (MedlinePlus).
Leg cramps: stretch your calves before bed (Mayo Clinic), or press your feet against the wall (MedlinePlus).
MedlinePlus says not to take any sleep aid, including over-the-counter and herbal products, without talking to your provider. Read can you take melatonin while pregnant for questions to ask.
For Partners: How to Help at 15 Weeks
Read the testing section together and come to the appointment if you can.
Take on chores that strain a sore back, like laundry baskets and grocery bags.
Learn the warning signs below so you can make the call if she is unsure.
Looking Ahead: What Comes Next
Week 16: about 4 3/4 inches crown to rump and 4 ounces (Mayo Clinic). UPMC says some people feel movement as early as now.
Week 17: toenails start developing, and the baby rolls and flips (Mayo Clinic).
Week 18: about 5 1/2 inches crown to rump and 7 ounces, and the baby might begin to hear sounds (Mayo Clinic). See 18 weeks pregnant.
Weeks 19 to 20: most people begin to feel kicks around week 19 (Cleveland Clinic), and the anatomy ultrasound comes around 20 weeks (MedlinePlus). See 20 weeks pregnant.
Call any time something worries you. MedlinePlus says to call your doctor or midwife in the second trimester for any bleeding, more or odorous vaginal discharge, a fever, chills or pain when urinating, or moderate or severe cramping or low belly pain.
Seek care right away. UPMC says preterm labor, preeclampsia and blood clots need emergency care, and lists these warning signs:
A severe headache that will not go away, or one with blurred vision or swelling of the face and hands, which UPMC says could indicate preeclampsia.
Trouble breathing, a racing heartbeat or chest pain.
A fever above 100.4 F.
Severe stomach pain, which could be contractions or preterm labor.
Swelling, redness and warmth in one leg, which could be a blood clot.
Vaginal bleeding, which could signal a problem with the placenta.
Thoughts of harming yourself.
Cleveland Clinic adds that belly pain with bleeding, contractions, fever or vomiting needs care right away. If you cannot reach your provider, go to the emergency room or call 911, and say how many weeks pregnant you are. This article is general education, not medical advice.
Frequently Asked Questions
How many months is 15 weeks pregnant?
About 3 1/2 months, which puts you in your 4th month, counting 4 weeks and a few days per month. Cleveland Clinic’s guide groups weeks 13 through 16 as month 4. You have about 25 weeks to go, and your provider will count in weeks.
How big is my baby at 15 weeks?
Our sources give no figure for week 15 itself. Mayo Clinic lists almost 3 1/2 inches crown to rump and about 1 1/2 ounces at week 14, and about 4 3/4 inches and 4 ounces at week 16. Cleveland Clinic compares the baby at the end of month 4 to an avocado.
What are common 15 weeks pregnant symptoms?
Mayo Clinic says nausea often eases and energy often returns in the second trimester, and describes a stuffy nose, nosebleeds, bleeding gums and dizziness. Cleveland Clinic says round ligament pain usually occurs from week 14 through 27, and UPMC lists heartburn. Call about bleeding, fever or severe pain.
Can you feel the baby move at 15 weeks?
Usually not yet. Mayo Clinic says movements can be seen on ultrasound around week 16 but are likely too small to feel. UPMC says most people feel movement around 20 weeks, some as early as 16, and Cleveland Clinic says most feel kicks around week 19.
Can you find out the gender at 15 weeks?
Not usually from a routine scan this week. Mayo Clinic says the sex likely becomes clearer around week 14, but MedlinePlus says the ultrasound that can determine it is done around 20 weeks. UPMC says the baby’s position can hide it, so tell the sonographer if you want a surprise.
How do I know if I need an amniocentesis?
It is your choice. MedlinePlus says you may want it if you are 35 or older, a screening result suggested a possible problem, or there is a family history of a genetic disorder. It is usually done between weeks 15 and 20. Talk it through with your provider before deciding.
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