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15 Weeks Pregnant: Growing Quickly, Bones and Hair Forming

Medically reviewed by

Verena Brehm, Midwife Jul 29, 2026

Line illustration of an orange: at 15 weeks pregnant your baby is about the size of an orange, roughly 9 to 12cm crown to rump

Line drawing of a 15-week foetus with a long slim body, defined neck and proportions close to a small baby

Line drawing of a woman's torso at 15 weeks pregnant, showing the uterus two thirds of the way to the navel with a visible bump

Your baby is the size of a

Orange

Between ~45g and 110g — bracketed from Mayo Clinic's weeks 14–16

~8.7–12 cm / ~3.4–4.7 in

Key Takeaways

At 15 weeks pregnant, your baby is growing quickly. According to Mayo Clinic, bone development continues and the scalp hair pattern is forming. Mayo places week 15 between week 14 (about 87mm / 45g) and week 16 (about 120mm / 110g), crown to rump.

You are settled into the second trimester now, the stretch many women find easier. Energy and appetite often return around this point, after the first-trimester fog lifts.

Your needs shift this trimester. The Society of Obstetricians and Gynaecologists of Canada (SOGC) advises about 340 extra calories per day and 27mg of iron daily, and staying active with at least 150 minutes of moderate activity each week.

Your Baby at 15 Weeks: Development & Growth

At 15 weeks pregnant, your baby is growing quickly. According to Mayo Clinic, bone development continues this week and the scalp hair pattern is forming. Mayo Clinic gives no length or weight for week 15; its nearest figures are week 14 (about 87mm / 45g) and week 16 (about 120mm / 110g) crown to rump — so week 15 sits somewhere in between.

Here is an honest note on size. Mayo Clinic does not publish a length or weight for week 15 — it gives figures for week 14 and week 16 instead. Mayo Clinic puts week 14 at "almost 3 1/2 inches (87 millimeters) long from the top of the head to the bottom of the tailbone, called crown to rump, and weigh about 1 1/2 ounces (45 grams)," and week 16 at "about 4 3/4 inches (120 millimeters) long from crown to rump and weigh about 4 ounces (110 grams)." Your baby this week likely falls between those two points — roughly 8.7cm to 12cm, and 45g to 110g.

The headline this week is bone. Mayo Clinic says that at 15 weeks your baby is growing quickly. Bone development continues and is becoming solid enough to show up on a scan.

Something smaller is happening too. Mayo Clinic notes that at 15 weeks "your baby's scalp hair pattern also is forming" — the map of where hair will grow is being drawn now, long before there is any hair to see.

Inside, things are shifting into place. Cleveland Clinic notes that around week 15 "some organs, like intestines and ears, are moving to their permanent location," and that the baby "still uses amniotic fluid to practice breathing," with the lungs beginning to develop. Your baby is also making more purposeful movements — though they are still too small for you to feel.

Your Body at 15 Weeks: Symptoms & Changes

At 15 weeks pregnant, many women feel the first-trimester fog has lifted, with energy and appetite returning. Other symptoms — tender breasts, constipation, backache, headaches, mood swings, leg cramps — can carry on. The Society of Obstetricians and Gynaecologists of Canada (SOGC) is clear that every pregnancy is different.

The most welcome change this week is often about energy. For many women the nausea of early pregnancy has eased, and the appetite that went missing starts to come back — which is well-timed, because your body needs a little more fuel now.

Other symptoms don't vanish overnight. The Society of Obstetricians and Gynaecologists of Canada (SOGC) lists tender or swollen breasts, constipation, gas and bloating, backaches, headaches, mood swings and leg cramps among the common discomforts of pregnancy. Any of these can still be part of your week 15.

Your body is also carrying more than the baby. SOGC explains that weight gain isn't just the baby — "your placenta, increased blood volume, larger breasts, and fat stores to support breastfeeding, also contribute." A little rounding through the middle is your body doing its work.

Mood is part of the picture. Fortunately, many women tend to feel more positive around this time, as their energy levels and general sense of well-being begin to return. However, the SOGC notes that while mild mood swings are common and not usually severe, "depression or disruptive mood swings are not normal and it is important to seek help for these more serious concerns." If your low mood is persistent, that is a reason to talk to your health care provider, not to wait it out.

If you sail through this week with barely a symptom, that is normal as well. SOGC puts it simply: "Every pregnant woman is different. Some will sail through pregnancy with very few symptoms, and others will be dogged with multiple discomforts throughout the 9 months."

What to Do at 15 Weeks Pregnant

NUTRITION AT 15 WEEKS PREGNANT

Add about 340 extra calories a day. The Society of Obstetricians and Gynaecologists of Canada (SOGC) states: "In the second trimester you need about 340 extra calories per day." It notes this "generally equates to 2 or 3 additional servings from any of Canada’s Food Guide’s food groups" — for example a piece of toast and a cup of milk, or an apple and ¾ cup of yogurt.
Get enough iron now. SOGC advises increasing "your daily iron intake to 27mg daily during the final six+ months of pregnancy to support an increase in red blood cells and fetal tissues" — and notes that, like most women, "you may need a good supplement to meet this need."
Build meals around a varied, nutrient-dense diet. SOGC points to Canada’s Food Guide, noting that "a varied, nutrient-dense diet" helps meet the needs of both you and your baby — with attention to fibre (aim for 28g daily), omega-3 DHA (aim for 1.4g daily) and iodine (aim for 250mcg daily). As your appetite returns, quality counts as much as quantity.
Include folate-rich foods and foods fortified with folic acid. Note that folate-rich foods don’t replace supplements. The Public Health Agency of Canada lists corn, oranges, beans, lentils and dark green vegetables like peas, spinach, broccoli and brussels sprouts as sources of folate — while stressing that "dietary sources on their own are not enough" to protect against neural tube defects.

WHAT SUPPLEMENTS TO TAKE AT 15 WEEKS PREGNANT

Keep taking 400mcg of folic acid daily. The Public Health Agency of Canada recommends "a daily multivitamin with 400 mcg (0.4 mg) of folic acid" for anyone who could become pregnant, and advises: "Continue taking folic acid throughout your pregnancy and while breastfeeding."
Don’t increase folic acid on your own. The Public Health Agency of Canada advises: "You should not increase your dose of folic acid beyond 1 mg per day without talking to your health care provider."
Use a prenatal that covers iron. SOGC notes that, like most women, "you may need a good supplement" to reach 27mg of iron a day — the second and third trimesters are when this matters most.
Consider your supplement combinations carefully. Because all-in-one prenatal products contain varying concentrations of different vitamins and minerals, it is important to always discuss specific formulations and daily dosages with a doctor to ensure they safely meet your individual health needs.

LIFESTYLE TIPS AT 15 WEEKS PREGNANT

Aim for at least 150 minutes of activity a week. The Society of Obstetricians and Gynaecologists of Canada (SOGC) advises that "pregnant women should accumulate at least 150 minutes of moderate intensity physical activity each week," spread across "at least 3 days a week, and up to 7 days a week." Walking, swimming and stationary cycling are all good options.
Keep the intensity comfortable. SOGC suggests you "keep the intensity in the zone where you can still hold a conversation and never exercise to exhaustion" — the returning second-trimester energy is best spent building a steady habit, not pushing hard.
Keep caffeine to 300mg a day. Health Canada recommends a maximum daily caffeine intake of 300 mg for people who are pregnant. Health Canada puts one 8oz (237ml) cup of brewed coffee at about 135mg — so roughly two cups is the ceiling, and that total includes tea, cola and chocolate.
Check any medication with your provider. SOGC advises that "ideally, you should not take any medication during pregnancy unless you and your health care provider determine that it is necessary" — and that natural or herbal products can also carry risks and should be discussed first.

When to Contact Your Doctor or Midwife

Most of week 15 is uneventful, and that is the point. But some symptoms should always be checked. Contact your doctor, midwife or other health care provider if you experience:

Any vaginal bleeding. The Society of Obstetricians and Gynaecologists of Canada (SOGC) advises: "It's important for you to take any vaginal bleeding seriously. Contact your health care provider as soon as you notice any bleeding." It notes that about one-third of pregnancies have some bleeding before the 20th week, and about half of these continue without further issues — but it should always be assessed.
Signs of infection, or heavy bleeding. SOGC advises that if you have "signs of infection like fever or heavy bleeding, you should see your care provider right away." If bleeding is heavy or you feel very unwell, seek emergency medical care immediately.
Persistent low mood or disruptive mood swings. SOGC advises that "depression or disruptive mood swings are not normal and it is important to seek help for these more serious concerns."
Nausea or vomiting so severe you cannot keep food down. If nausea lingers to the point where you are missing meals or losing weight, that is not something to push through — see your health care provider, as other treatments can help.
Severe abdominal pain, or any symptom that frightens you. Sudden, severe pain warrants urgent assessment — seek emergency medical care immediately if it is intense or you feel faint. For anything that simply worries you, your health care provider is there for exactly that.

Frequently Asked Questions

How big is my baby at 15 weeks pregnant?

Mayo Clinic does not give a length or weight for week 15 specifically. Its nearest figures are week 14 — "almost 3 1/2 inches (87 millimeters)" and "about 1 1/2 ounces (45 grams)" — and week 16, "about 4 3/4 inches (120 millimeters)" and "about 4 ounces (110 grams)," both crown to rump. So at 15 weeks your baby sits between those points: roughly 8.7cm to 12cm, and 45g to 110g. Length is measured crown to rump at this stage because the legs are still curled.

What is my baby doing at 15 weeks pregnant?

According to Mayo Clinic, at 15 weeks "your baby is growing quickly. Bone development continues," and "your baby’s scalp hair pattern also is forming." Mayo Clinic adds that soon the bones will be visible on ultrasound images. Cleveland Clinic notes that around now some organs, like the intestines and ears, are moving to their permanent location.

What symptoms are normal at 15 weeks pregnant?

Many women find energy and appetite returning as first-trimester nausea eases. The Society of Obstetricians and Gynaecologists of Canada (SOGC) lists tender breasts, constipation, backaches, headaches, mood swings and leg cramps among common pregnancy symptoms, any of which can continue. SOGC also notes that some women have very few symptoms, which is equally normal. Any vaginal bleeding, however, is not routine — SOGC advises contacting your health care provider as soon as you notice any bleeding.

How much should I be eating at 15 weeks pregnant?

The Society of Obstetricians and Gynaecologists of Canada (SOGC) states that "in the second trimester you need about 340 extra calories per day." It notes this generally equals 2 or 3 additional servings from Canada’s Food Guide’s food groups — such as a piece of toast and a cup of milk. It’s a modest, quality-focused increase, not eating for two.

How much caffeine is safe at 15 weeks pregnant?

Health Canada recommends a maximum daily caffeine intake of 300 mg for people who are pregnant. Health Canada puts one 8oz (237ml) cup of brewed coffee at about 135mg, so roughly two cups a day is the ceiling — and that total should include tea, cola and chocolate, which also contain caffeine.

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Sources & References

Public Health Agency of Canada — Folic acid, healthy pregnancy and neural tube defect prevention
Health Canada — Caffeine in Foods (recommended maximum daily intake)
SOGC — Healthy eating
SOGC — Exercise during pregnancy
SOGC — Symptoms of pregnancy
SOGC — Weight gain during pregnancy
SOGC — Medications and drugs during pregnancy
SOGC — Pregnancy Loss
Mayo Clinic — Fetal development: The 2nd trimester (Week 15, with Week 14 and Week 16 for size)
Cleveland Clinic — Fetal Development: Week-by-Week Stages of Pregnancy

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