Week 15 · Second trimester
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Week 15 fetal development and pregnancy guide — length about 10.1cm, weight 约70g (about the size of a an apple)

Your baby is now about 10.1cm and 约70g, about the size of a an apple.

Medical references: WHO INTERGROWTH-21st · China Prenatal & Pregnancy Care Guide · ACOG

View each day of week 15 →

Week 15 fetal development milestones: length / weight / ultrasound data

Key developmental changes during week 15:

  • Bones keep ossifying, and the skeleton of the limbs and spine is clearly visible on ultrasound
  • Hair and eyebrows begin to sprout, with active scalp hair follicles
  • The ears move up from the neck to the correct position on both sides of the head; the auditory system begins to develop (but still can’t hear yet)
  • The legs are longer than the arms, and body proportions are closer to a newborn’s
  • The skin is thin and semi-transparent, with subcutaneous vessels clearly visible
  • Sweat glands begin forming, laying the groundwork for temperature regulation after birth
  • It begins swallowing amniotic fluid and doing sucking movements; the breathing muscles (diaphragm) keep developing, preparing for breathing after birth
  • The eyes have moved to the front of the face and iris pigment begins to deposit, but the eyelids remain closed
  • More coordinated movements: stretching the limbs, clenching fists, turning around
  • About 10.1cm — the size of an apple — weighing about 70g
Illustration of your baby about the size of an apple at week 15 (about 10.1cm/约70g)
Week 15 size: about the size of a an apple
BPD (biparietal diameter)30.1mmWidth across the head; reflects brain development
AC (abdominal circumference)90.4mmAbdomen circumference; reflects nutrient absorption
FL (femur length)15.7mmThigh bone length; tracks gestational age
Ultrasound parameters at week 15: BPD 30.1 mm, AC 90.4 mm, FL 15.7 mm (median reference)
Week 15 three core ultrasound parameters (median; varies by individual)

* Values are medians from WHO/China standards; individual variation is normal. References: WHO INTERGROWTH-21st, China Prenatal & Pregnancy Care Guide, ACOG guidelines.

Week 15 daily development

Your baby quietly grows every day of week 15. Tap any day to see fetal development, maternal changes, and daily guidance for that day.

99Day 1The baby’s hair and eyebrows are sprouting from the follicles, and its little ears have moved steadily up to the correct position on both sides of the head — the whole outline is looking more and more like a complete newborn. If today’s ultrasound angle is right, you may see it resting a hand on its cheek, quiet like a little philosopher in thought. Send a photo to the father-to-be so he can share this faraway surprise.100Day 2Swap today’s white rice for multigrain rice — a handful each of brown rice, millet and quinoa mixed and soaked half an hour before cooking; soft and chewy, with several times the fiber of white rice. Pregnancy hormones slow the gut; from mid-pregnancy mixing coarse and fine grains at every meal visibly improves bowel regularity. If your gut is sensitive and bloats easily, use a smaller brown-rice ratio, cook 10 minutes longer, and gradually increase after it softens.101Day 3Pick a set time each day (a quiet moment after a meal) to gently talk to the belly for 5 minutes — “Baby, mommy ate fish today” / “Dad just called to ask how you are” — in an ordinary conversational way, without chasing volume or “educational meaning.” Your baby’s hearing isn’t fully built yet, but you’re building the parent-child bond and relaxing yourself.102Day 4Pregnancy rhinitis acting up? Estrogen swelling the nasal lining causes congestion in about 20-30% of pregnant women. Have your partner run a humidifier (keep humidity at 40-60%), use saline spray or drops before bed, and prop your head slightly with two pillows at night. When symptoms are bad, don’t use compound cold medicines containing “pseudoephedrine” — see an ENT doctor to rule out infection and choose a pregnancy-safe plan.103Day 5If you haven’t booked the mid-term screen or NIPT yet, call today. The mid-term window is weeks 16-18; NIPT can be done from week 12. Choose either: the mid-term screen is lower-cost with about 70-80% detection, NIPT above 99% but pricier. Older mothers (≥35), NT abnormalities and a family history of chromosome problems prioritize NIPT.104Day 6Weigh yourself on a fixed day each week (say Saturday morning, on an empty stomach and after a bowel movement) and record it. In mid-pregnancy a standard weight gains about 0.4-0.5kg a week; a cumulative gain of about 2-5kg by week 15 is normal. A plain electronic scale is enough — the key isn’t any single week but the smooth trend over 4-5 weeks. If the gain exceeds 0.8kg for two straight weeks, review diet and exercise and mention it at your prenatal visit.105Day 7Start researching the three big items — stroller, car seat and crib. No need to buy today but do the homework. For the stroller look at folded size (whether it fits your trunk), suspension and adjustable seat depth; the car seat must be new (used ones may have been crashed or expired), check for the national approval mark and newborn-fit notes; and crib rail gaps shouldn’t exceed 6cm. Make a “three-big-items comparison table” to record budget and pros/cons.

Week 15 belly changes

Illustration of belly changes at week 15: uterine position and abdominal prominence

At week 15 (second trimester) the uterus rises from the pelvis into the abdomen and most mums start to "show" — a gentle bump. First-time mums usually show a little later than mums who've been pregnant before; the fundal height sits between the navel and pubic bone.

Week 15 maternal body changes and common symptoms

  • The fundal height sits about between the pubic bone and the navel, and the belly begins to protrude slightly
  • Weight rises steadily; about 0.4-0.5kg a week for a standard BMI in the second trimester
  • Nasal congestion or sinus fullness may occur (pregnancy rhinitis), affecting about 20-30% of women — estrogen makes the nasal lining swell; a humidifier and saline drops help
  • Gums may bleed or swell (pregnancy gingivitis), affecting about 60-75% of women — hormones make the gums more sensitive to plaque; keep up the soft-bristle brush + floss and book a dental visit
  • Energy returns and fatigue eases — entering the relatively comfortable second trimester
  • Appetite increases; watch total intake to avoid gaining too fast
  • The breasts keep enlarging; a little colostrum may ooze (normal — don’t squeeze)
  • Skin may become oilier or break out; pigmentation (areolas, abdominal midline) begins to darken

Week 15 nutrition advice and recommended recipes

This week’s focus: dietary fiber + keep covering key nutrients. Per authorities, mid-pregnancy needs about 340 extra kcal a day (ACOG, ≈ a glass of milk + an egg + a small handful of nuts); daily targets: ①fiber 25-30g — replace refined grains with whole grains, plus legumes, potatoes and produce; ②calcium 1000mg (ACOG) — milk, soy products, sesame paste; ③iron 27mg (ACOG) — red meat, liver (≤50g/week) and spinach paired with vitamin C; ④DHA 200-300mg — low-mercury fish 2-3 times a week or algae oil; ⑤folic acid 400-800μg, ideally continuing through the whole pregnancy; ⑥iodine 230μg — iodized salt, seaweed/kelp; ⑦quality protein about 70g. In the comfortable phase after morning sickness has passed, still don’t overeat — keep it balanced. Avoid alcohol, cold-raw unpasteurized milk and high-mercury fish; caffeine ≤200mg/day.

DHA200-300mgBrain & vision development
Recommended recipeMultigrain rice

White rice + brown rice + millet + quinoa, rich in fiber and B vitamins; replacing refined white rice helps prevent constipation and steady blood sugar. Soak in advance for a softer cook; if your gut is sensitive, keep the brown-rice ratio lower to avoid bloating.

Week 15 prenatal education guide

First, to be clear: there is currently no strong evidence that specific stimulation makes a baby smarter; the core of prenatal care is helping the mother relax, feel good and go with the flow. This week the baby’s auditory system is just starting to develop and still can’t hear, so “playing music for the baby to remember” doesn’t apply yet. More reliable approaches — language: gently talk to the belly 5-10 minutes at a fixed time daily, reading picture books or recounting your day; it helps the mother relax and builds the bond. Music: choose soothing classical music or natural white noise, volume under 60 decibels, 15-20 minutes a day — the goal is your own relaxation. Don’t chase “the baby remembering”; enjoy the process.

Week 15 partner's role

① Make a pregnancy budget and shopping list with your partner: do homework on big items (crib, stroller, car seat) early. ② Accompany her to book a dental check — pregnancy gingivitis is common, and the second trimester is the safe treatment window. ③ Talk to the belly or sing the same song at a fixed time daily to build early parent-child connection; newborns respond more soothingly to a father’s voice heard repeatedly in pregnancy. ④ Help ease nasal congestion: prepare a humidifier and saline nasal spray, and remind her to hydrate and rest.

Week 15 checkup reminders

The NT window (weeks 11-13⁺⁶) has passed, so chromosome screening now goes one of two routes: ①NIPT (cell-free DNA, generally doable from week 12, >99% detection for trisomy 21 and about 95-99% for trisomy 18, only a maternal blood draw with no miscarriage risk); ②or book the weeks 16-18 mid-trimester screen as the alternative. What the mid-term screen checks: a maternal blood draw measuring AFP, hCG, uE3 and Inhibin A to assess the risk of trisomy 21, trisomy 18 and neural-tube defects. Which to choose combines age, NT result and your doctor’s advice. Book it from this week — don’t miss the weeks 16-18 window.

Week 15 key concerns

Increase dietary fiber to prevent constipationSupplement zinc, calcium and ironBook the mid-trimester screen / NIPTPrevent pregnancy rhinitis30 minutes of moderate-intensity exercise a day (ACOG recommends 150 minutes a week)

Signs that need immediate care at week 15

Contact your obstetrician or seek care promptly for any of the following: ①vaginal bleeding or brown discharge that doesn’t stop; ②sudden fluid gushing from the vagina (possible premature rupture of membranes); ③persistent or severe abdominal pain, with fever or regular contractions-like tightening; ④fever above 38°C that doesn’t come down; ⑤severe headache, blurred vision or severe upper-abdominal pain (be alert for pregnancy-induced hypertension — it mostly occurs after week 20 and is extremely rare at week 15, but must still be checked if it appears); ⑥painful urination, frequent/urgent urination or blood in the urine (urinary tract infection); ⑦swelling, heat or pain in one leg (be alert for a blood clot); ⑧sudden marked edema or a jump in weekly weight.

Week 15 frequently asked questions

What about nasal congestion / pregnancy rhinitis at week 15?
About 20-30% of pregnant women get nasal congestion, mostly from estrogen swelling the nasal lining. A humidifier, saline spray or drops, and sleeping with the head a little raised help; avoid compound cold medicines containing pseudoephedrine. If it’s severe or comes with thick yellow mucus and fever, see an ENT doctor first to rule out infection.
How big should my belly be at week 15? Does showing look normal?
The fundus sits between the pubic bone and the navel; first-time mothers usually just start showing faintly and it may not show in clothing; women who’ve given birth show earlier. Fundal height measured by the doctor is the gold standard for growth — no need to compare with others.
Should I do the mid-trimester screen at week 15? When?
The mid-trimester screen is generally arranged at weeks 16-18; you can book it this week. It’s a maternal blood draw measuring AFP/hCG/uE3/Inhibin A to assess chromosome and neural-tube-defect risk. If the NT window passed and you want results earlier, you can also go straight to NIPT (generally from week 12).
How do I choose between the mid-term screen and NIPT?
The mid-term screen is low-cost but detects trisomy 21 at about 70-80%; NIPT has a detection rate over 99%, no miscarriage risk, but higher cost. Older mothers (≥35), NT abnormalities, or a history of chromosome problems more warrant NIPT — combined with your doctor’s advice.
Do I still need folic acid at week 15?
ACOG recommends 400-800μg of folic acid daily from before pregnancy through the first trimester to prevent neural-tube defects, usually through week 12; after that, you can switch to a pregnancy multivitamin containing folic acid as your doctor directs — follow your prenatal checkup.
Can I feel fetal movement at week 15?
Usually not yet. First-time mothers typically first feel movement at weeks 18-22; women who’ve given birth may feel it at weeks 16-18. At week 15 the baby is active but small with plenty of cushioning, so not feeling it yet is normal.
How do I read my week-15 ultrasound report?
Week-15 ultrasound three measures: BPD about 30mm (biparietal diameter — head width), AC about 90mm (nutrition and liver development), and FL about 16mm (femur length). All three within the week’s standard range indicates coordinated development; take your obstetrician’s overall reading as authoritative — a single value slightly off isn’t necessarily abnormal.
Is there a recommended amount of exercise for pregnancy?
Yes. ACOG recommends about 150 minutes of moderate-intensity activity per week (walking, prenatal yoga, etc.) for pregnant women without complications, split over 5 days at about 30 minutes each. Entering the comfortable phase at week 15, exercise regularly; avoid strenuous activity and abdominal pressure — stop and seek care if pain or bleeding occurs.
Should I get a flu shot in pregnancy?
Yes, recommended. The CDC and ACOG both recommend the inactivated flu vaccine for pregnant women — pregnant women have a higher risk of severe outcomes, the vaccine protects both mother and baby, and it is safe at all stages. You can get it during flu season (September to April); tell the vaccinator you are pregnant.
Can I have sex at week 15?
In the second trimester the fetus is relatively stable; as long as there is no low-lying placenta, bleeding, cervical insufficiency or threatened miscarriage, gentle sex is usually fine — choose positions that don’t press the abdomen and move gently. If you feel unwell or your doctor advises avoidance, pause.
How much weight gain is normal at week 15?
From week 15, a standard BMI gains about 0.4-0.5kg a week, with a cumulative gain of about 2-5kg by week 15 being common. Watch the overall trend rather than any single week; talk to your doctor if too fast or slow, and you can manage by BMI with a pregnancy weight-gain calculator.
What about constipation at week 15?
Pregnancy hormones slow intestinal movement and the growing uterus presses the bowel, so constipation is common. Drink 1.5-2L of water a day, eat more whole grains, fruit and vegetables for fiber, walk after meals, and use the toilet regularly without sitting long. If severe, don’t buy medicine on your own — ask a doctor for a pregnancy-safe laxative.
What should I watch with sleep position at week 15?
From mid-pregnancy you can practice left-side sleeping — it increases uterine-placental blood flow and improves oxygen to the baby. A pregnancy pillow helps support the abdomen and legs; you don’t have to stay on the left all night — comfort and good sleep matter. Avoid face-down pressure on the belly.
What foods should I avoid at week 15?
Avoid raw/undercooked meat, fish and eggs (toxoplasmosis, Listeria), high-mercury large fish (shark, swordfish, etc.), unpasteurized dairy, alcohol (no amount is safe), caffeine ≤200mg a day, and excess liver (vitamin A overdose). Well-cooked food and thorough heating are safer.
Can I fly at week 15?
The second trimester is a better flying window; most airlines don’t require a doctor’s note before week 32 and request one after (mostly banning after week 36). Choose an aisle seat to move around, hydrate, and wear compression socks to prevent clots. If you have bleeding, pain or placental problems, consult your doctor before traveling.
Is back pain at week 15 normal?
In mid-pregnancy the center of gravity shifts forward and relaxin loosens ligaments, so back ache gradually grows. Avoid long standing or sitting, wear supportive low-heeled shoes, place a pregnancy pillow between the legs when side-lying, and do prenatal yoga and pelvic-floor exercises. Severe one-sided pain or pain with bleeding/fever warrants care.
Is more discharge at week 15 normal?
Higher estrogen increases discharge; milky-white or clear with no odor is normal. Watch for yellow-green color, fishy smell or itching (infection), or a sudden large gush of watery fluid (premature rupture of membranes) — seek care if these occur. Wear cotton underwear, keep clean, and don’t do vaginal douching.
Do I need calcium and iron at week 15?
ACOG recommends about 1000mg of calcium and 27mg of iron a day in mid-pregnancy. For calcium prioritize milk, soy products and sesame paste; for iron prioritize red meat, liver (≤50g/week) and spinach paired with vitamin C. Whether to add supplements depends on diet and checks; taking iron and calcium separately absorbs better.
Should I book the anatomy scan at week 15?
The anatomy scan (systematic scan) is at weeks 20-24, and popular hospitals have tight slots often needing booking weeks ahead. Though this week is early, start paying attention and book it around the 16-18-week screen to avoid missing the best week range.
⚡The gestational-development data on this tool is compiled from the WHO INTERGROWTH-21st fetal growth standards, ACOG (American College of Obstetricians and Gynecologists), and the Chinese Medical Association's Guidelines for Pre-conception and Prenatal Care, and is reviewed for consistency by obstetrics consultants against those authoritative standards. Daily developmental tips, maternal changes, and nutrition advice follow an evidence-based approach. Note that fetal length is measured differently by week: crown–rump length (CRL) at or before week 20, and crown–heel length (CHL) from week 21 — values either side of week 21 are not directly comparable, which is a normal measurement change.

Data sources & notes

This tool provides algorithm-based estimates from the authoritative standards above for pregnancy time planning and general reference. It does not replace a doctor's diagnosis or individualized medical advice; follow your obstetrician for all prenatal care decisions.

Week 15 daily focus

Key daily tips for this week; tap any item to view the full development and guidance for that day.

Day 1The baby’s hair and eyebrows are sprouting from the follicles, and its little ears have moved steadily up to the correct position on both sides of the head — the whole outline is looking more and more like a complete newborn. If today’s ultrasound angle is right, you may see it resting a hand on its cheek, quiet like a little philosopher in thought. Send a photo to the father-to-be so he can share this faraway surprise.Day 2Swap today’s white rice for multigrain rice — a handful each of brown rice, millet and quinoa mixed and soaked half an hour before cooking; soft and chewy, with several times the fiber of white rice. Pregnancy hormones slow the gut; from mid-pregnancy mixing coarse and fine grains at every meal visibly improves bowel regularity. If your gut is sensitive and bloats easily, use a smaller brown-rice ratio, cook 10 minutes longer, and gradually increase after it softens.Day 3Pick a set time each day (a quiet moment after a meal) to gently talk to the belly for 5 minutes — “Baby, mommy ate fish today” / “Dad just called to ask how you are” — in an ordinary conversational way, without chasing volume or “educational meaning.” Your baby’s hearing isn’t fully built yet, but you’re building the parent-child bond and relaxing yourself.Day 4Pregnancy rhinitis acting up? Estrogen swelling the nasal lining causes congestion in about 20-30% of pregnant women. Have your partner run a humidifier (keep humidity at 40-60%), use saline spray or drops before bed, and prop your head slightly with two pillows at night. When symptoms are bad, don’t use compound cold medicines containing “pseudoephedrine” — see an ENT doctor to rule out infection and choose a pregnancy-safe plan.Day 5If you haven’t booked the mid-term screen or NIPT yet, call today. The mid-term window is weeks 16-18; NIPT can be done from week 12. Choose either: the mid-term screen is lower-cost with about 70-80% detection, NIPT above 99% but pricier. Older mothers (≥35), NT abnormalities and a family history of chromosome problems prioritize NIPT.Day 6Weigh yourself on a fixed day each week (say Saturday morning, on an empty stomach and after a bowel movement) and record it. In mid-pregnancy a standard weight gains about 0.4-0.5kg a week; a cumulative gain of about 2-5kg by week 15 is normal. A plain electronic scale is enough — the key isn’t any single week but the smooth trend over 4-5 weeks. If the gain exceeds 0.8kg for two straight weeks, review diet and exercise and mention it at your prenatal visit.Day 7Start researching the three big items — stroller, car seat and crib. No need to buy today but do the homework. For the stroller look at folded size (whether it fits your trunk), suspension and adjustable seat depth; the car seat must be new (used ones may have been crashed or expired), check for the national approval mark and newborn-fit notes; and crib rail gaps shouldn’t exceed 6cm. Make a “three-big-items comparison table” to record budget and pros/cons.

Content sources & notes

This guide references WHO INTERGROWTH-21st standards, the China Prenatal & Pregnancy Care Guide, ACOG clinical guidelines and BabyCenter (medically reviewed).

This page is educational pregnancy information for general reference and does not replace the diagnosis or advice of a licensed healthcare provider.

View the full fetal BPD/AC/FL reference table (weeks 14–42) →

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