Week 30 · Third trimester
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Week 30 fetal development and pregnancy guide — length about 39.9cm, weight 约1319g (about the size of a a cabbage)

Your baby is now about 39.9cm and 约1319g, about the size of a a cabbage.

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

View each day of week 30 →

Week 30 fetal development milestones: length / weight / ultrasound data

Key developmental changes during week 30:

  • The number of brain tissues and neural connections surges, and the neuron networks connect at high speed.
  • Brown fat begins to accumulate, providing energy to maintain body temperature after birth.
  • The skin begins to produce melanin, determining the baby’s final skin colour (mostly settled within 6 months after birth).
  • The lanugo (fine body hair) begins to fall off in waves and the hair keeps growing.
  • The eyes can open wide to see blurry shapes, and the head turns toward bright light shining on the belly.
  • By swallowing amniotic fluid the baby experiences the taste of the mother’s diet, and taste preferences after birth begin to form.
  • Amniotic-fluid volume is near its peak (about 800-1000ml) and gradually declines after weeks 32-34.
  • Subcutaneous fat increases, the cheeks are plump and the hands and feet grow rounder.
  • Most babies have already turned head-down (weeks 30-32 are the key period for the fetal position to settle).
  • About 39.9cm long, about the size of a big cabbage, weighing about 1319g.
Illustration of your baby about the size of a cabbage at week 30 (about 39.9cm/约1319g)
Week 30 size: about the size of a a cabbage
BPD (biparietal diameter)76mmWidth across the head; reflects brain development
AC (abdominal circumference)257.3mmAbdomen circumference; reflects nutrient absorption
FL (femur length)55.5mmThigh bone length; tracks gestational age
Ultrasound parameters at week 30: BPD 76 mm, AC 257.3 mm, FL 55.5 mm (median reference)
Week 30 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 30 daily development

Your baby quietly grows every day of week 30. Tap any day to see fetal development, maternal changes, and daily guidance for that day.

204Day 1Your baby can now clearly tell your voice apart from others’ — your pitch, rhythm and emotional tone are already the most familiar voice in its world. Today, facing your belly, tell it about your small daily things in the most ordinary tone: "I had red-bean porridge today" "It rained a little just now, the window’s open and it’s cool" — no need to read formally; just connect with your everyday voice. This familiarity turns into a sense of security after birth.205Day 2Bloated and full after a few bites? Use the "reverse-formula" rule: split the total food of your three main meals into 5-6 small portions, stop at seven-or-eight-percent fullness (you could eat a few more bites but aren’t hungry) at each; sit or stand upright for 15 minutes after meals so the uterus doesn’t squeeze the stomach further upward; don’t eat in the 2-3 hours before bed. If bloating comes with severe acid reflux and a burning feeling when swallowing, prop your upper body up 30 degrees when sleeping.206Day 3Listen to 15 minutes of soothing natural sound daily (waves, birdsong or solo piano) at no higher than 60 decibels. The point isn’t "letting the baby appreciate music to cultivate taste" — there’s no scientific evidence for that. The point is that when you relax, your body releases endorphins and lowers cortisol, helping you relax the body and mind, improve sleep and steady your mood. Play music for yourself; your baby enjoys the "knock-on benefits" of your relaxation.207Day 4This week attend a hospital or online delivery-experience class (2-3 hours) covering: a 3D animation of the delivery process, Lamaze breathing practice, delivery-position choices and birthing-ball use, the mechanism and timing of epidural analgesia, and the division of roles for dad in the labour ward. Bring a pen and notebook for key information and go with dad — he needs to know the labour ward isn’t "a place to wait and hold the baby".208Day 5Amniotic-fluid volume is near its pregnancy peak this week (about 800-1000ml), declining gradually after weeks 32-34. Your baby’s urine is the main source of amniotic-fluid circulation, and the volume is an important window on placental function and fetal health. If the small scan finds low or high amniotic fluid, the doctor will advise drinking more water and monitoring more often — don’t "down water" on your own; follow the obstetric guidance.209Day 6Tell true "broken waters" from "leaking urine": broken waters is an uncontrollable continuous flow of clear or slightly yellow fluid that you can’t stop even by clenching the perineal muscles; leaking urine is a small spray when you cough or laugh and can be paused by contracting the perineum. If you suspect broken waters but aren’t sure — lie flat immediately, use a clean sanitary pad to observe the colour, and if it stays wet treat it as real broken waters and seek care; better to go to the hospital and find it was a false alarm than to wait at home.210Day 7Small-scan day (or confirm the date): today look on the B-ultrasound screen at whether BPD (biparietal diameter), AC (abdominal circumference) and FL (femur length) are in the normal range, plus amniotic-fluid volume, placental position and umbilical blood flow. Ask the doctor three questions: "What position is the fetus in now?" "Is the placental position normal?" "Is the umbilical-blood-flow resistance value in the normal range?" — note the answers in your phone memo for comparison at the next visit.

Week 30 belly changes

Illustration of belly changes at week 30: uterine position and abdominal prominence

At week 30 (third trimester) the uterine fundus keeps rising closer to the sternum. Your belly is clearly rounded and your waistline and fundal height grow quickly, so pay more attention to balance and safety in daily movement.

Week 30 maternal body changes and common symptoms

  • The uterine fundus is about 10cm above the navel.
  • Cumulative weight gain is about 9-13kg (about 0.4-0.5kg a week in the third trimester for a standard BMI).
  • The frequency of Braxton Hicks false contractions may increase — painless and irregular.
  • Bloating, heartburn and constipation may worsen (the uterus presses up on the stomach and pregnancy hormones slow digestion).
  • Leg swelling, cramps and varicose veins may become more obvious.
  • Sleep difficulty grows (frequent urination, trouble turning over).
  • Abdominal skin stretch-itching and stretch marks may become more obvious.
  • The breasts enlarge, colostrum is secreted, and some people lightly leak urine.

Week 30 nutrition advice and recommended recipes

In the third trimester the growing uterus presses the stomach and bloating is easy, so keep eating smaller meals more often: 5-6 meals a day, seven-or-eight-percent full each, chew slowly. Daily targets: quality protein about 80-90g, iron about 27-29mg, calcium 1000mg, DHA 200-300mg, fiber 25-30g, iodine 230μg. Keep controlling sugar (strict for GDM). Avoid alcohol, raw or unpasteurised milk products, high-mercury fish, caffeine ≤200mg a day.

DHA200-300mgBrain & vision development
Recommended recipeCarrot chicken porridge

Porridge is soft, easy to digest and gentle on the stomach; chicken shreds bring quality protein and carrot brings β-carotene. You can add a little chopped greens for fiber; if blood sugar runs high, control the portion and pair it with an egg or soy product for a steadier rise.

Week 30 prenatal education guide

The core of "fetal education" is still to help the mother-to-be relax and go with the flow; there is currently no strong evidence that any specific stimulation makes the baby smarter, and there is no such thing as "cultivating musical taste". The baby’s hearing is keen and it reacts to outside sounds; listening to soothing music mainly helps you relax and steady your mood. What you can do: at a fixed time each day choose soothing classical music or natural white noise at a volume ≤60 decibels for 15-20 minutes as a relaxation ritual for you and your partner; combine with fixed gentle talking for 5-10 minutes and belly stroking. Don’t chase "which music the baby likes" — enjoying the time together is the most practical.

Week 30 partner's role

①Attend a hospital delivery-experience class or online delivery-knowledge lecture with your partner, covering the delivery process, pain-relief methods and postpartum breastfeeding. ②Help relieve her bloating: prepare healthy small meals, avoid greasy and spicy food, and walk with her after meals to aid digestion. ③Talk or sing close to the belly at a set time daily to build a father’s voice the baby recognises. ④Keep filling the hospital bag and researching baby products so that it’s basically complete before week 36.

Week 30 checkup reminders

Weeks 30-32: the small scan (anomaly-late ultrasound) to assess fetal growth, amniotic-fluid volume, placental position, umbilical blood flow and fetal position — complete it this week or next. Routine visit: weight, blood pressure, fundal height, abdominal circumference, fetal-heart auscultation and urinalysis. Since week 28, visits are every two weeks with daily fetal-movement counting. You can also learn about the 35-37-week GBS screening and the 27-36-week Tdap vaccine.

Week 30 key concerns

Complete the small scanEat smaller meals more often to relieve bloatingAttend a delivery courseWatch the fetal position (most are head-down)30 minutes of moderate exercise daily (ACOG recommends 150 minutes a week across pregnancy)

Signs that need immediate care at week 30

If any of the following occurs, contact your obstetrician or seek care promptly: ① sudden vaginal leakage of fluid (persistent, colourless, odourless — possible premature rupture of membranes) — lie flat immediately with your hips raised and seek care; ② clearly reduced fetal movement (under 10 in 2 hours or down by more than half from usual); ③ regular contractions (once every 10 minutes or more often) with lumbar heaviness/downward pressure (watch for preterm labour); ④ persistent severe headache, blurred vision or upper-abdominal pain with raised blood pressure or sudden swelling (watch for preeclampsia); ⑤ itching all over, especially palms and soles with no rash (watch for ICP); ⑥ a fever over 38℃ that does not come down; ⑦ swelling, warmth and pain in one leg or sudden breathing difficulty and chest pain (watch for a clot/pulmonary embolism); ⑧ sudden obvious swelling or persistent abdominal pain.

Week 30 frequently asked questions

What does it feel like when my waters break?
An uncontrollable continuous flow of clear fluid (colourless or slightly yellow, odourless or slightly sweet) — unlike urine, it still flows even when you hold it in. If you suspect broken waters, lie flat immediately, raise your hips and seek care as soon as possible; don’t walk around.
Is it normal for the baby to be head-down at week 30?
Yes, it’s the ideal position. Most babies turn head-down on their own between weeks 30-32. For breech or transverse position you can try the knee-chest exercise (15 minutes morning and evening); after week 34 the doctor assesses whether to do an external cephalic version (ECV). Follow your prenatal-care doctor’s advice.
When is the small scan done?
The small scan is generally arranged at weeks 30-32 — complete it this week or next. It assesses fetal growth, amniotic-fluid volume, placental position and maturity, fetal position and umbilical blood flow — an important third-trimester monitoring scan; popular hospitals need advance booking.
How much weight gain is normal at week 30?
A cumulative gain of about 9-13kg by week 30 is common. For a standard BMI, the third trimester is about 0.4-0.5kg a week and the whole pregnancy recommends about 11.5-16kg. Watch the overall trend and manage by BMI with a weight-gain calculator.
Bloated and can’t eat at week 30 — what should I do?
A growing uterus pressing the stomach and pregnancy hormones slowing digestion cause common bloating. Eat smaller meals more often (5-6 meals a day at seven-or-eight-percent fullness), chew slowly, walk after meals to aid digestion, and avoid greasy, spicy food and carbonated drinks. Consult a doctor if symptoms are severe.
Can the baby tell my voice apart at week 30?
Yes. This week the baby’s hearing is keen and it can tell the mother’s voice from strangers’, growing calmer with your familiar voice. Talking gently at a set time daily or having dad read picture books is a great way to bond, but don’t interpret it as "hearing training".
Are the fetal movements regular at week 30?
Most babies have obvious active periods (after meals, at night). Since week 28 you should count fetal movements daily: one hour in the morning, afternoon and evening each; ≥10 within 2 hours is normal. If it’s clearly under 10 in 2 hours or down by more than half from usual, seek care immediately.
How do I read the week-30 ultrasound report?
The three measurements at 30 weeks: BPD (biparietal diameter) about 76.0mm, AC (abdominal circumference) about 257.3mm, and FL (femur length) about 55.5mm, reflecting head, abdomen and leg development. If the three are in step, growth is good; a single slight deviation isn’t necessarily abnormal — go by your obstetrician’s overall assessment.
Is it normal to have many false contractions at week 30?
An increasing frequency of Braxton Hicks false contractions is common in the third trimester: brief tightening and hardening of the belly, painless and irregular, disappearing with rest or a change of position — the uterus "warming up". If they become regular, with pain or lumbar heaviness down, seek care to rule out preterm labour.
Is there a recommended exercise duration in pregnancy?
ACOG advises women without complications about 150 minutes of moderate-intensity exercise accumulated weekly (walking, prenatal yoga, swimming), split over 5 days at about 30 minutes a day. In the third trimester focus on walking and stretching; avoid intense exercise and pressure on the abdomen; stop and seek care for pain or bleeding.
Can I still get vaccines in the third trimester?
Yes. The CDC and ACOG recommend the Tdap whooping-cough vaccine at weeks 27-36 to prevent Pertussis in the baby; the inactivated flu vaccine can also be given in flu season. Both are pregnancy-safe vaccines; tell them you’re pregnant before vaccination.
Can I have sex at week 30?
If there’s no placenta praevia, bleeding, cervical insufficiency or threatened preterm labour, gentle sex is fine using positions that don’t press on the belly and with gentle movements. The closer to term, the more caution in the third trimester; pause if unwell or the doctor advises against it; seek care for post-sex bleeding, pain or leaking fluid.
What about leg cramps and swelling at week 30?
When a cramp hits, flex the foot and massage the calf; prevention relies on supplementing calcium and magnesium, drinking water and stretching before bed. For swelling, raise your legs, lie on your left side, walk to promote return flow, and moderately limit salt. If swelling suddenly worsens, spreads to the face and hands, or comes with headache or vision changes, check blood pressure to rule out preeclampsia.
What should I avoid eating at week 30?
Avoid raw or undercooked meat, fish and eggs, high-mercury large fish, unpasteurised dairy, alcohol, caffeine over 200mg a day, and excess animal liver. If you have GDM, strictly control refined sugar and sugary drinks as well.
What about heartburn at week 30?
Eat smaller meals more often and chew slowly, sit or stand for 30 minutes after meals before lying down, avoid eating in the 2-3 hours before bed, avoid spicy, greasy, overly sweet food and carbonated drinks, and prop up your upper body when sleeping. In serious cases, use a pregnancy-safe antacid under a doctor’s guidance.
What about constipation and haemorrhoids at week 30?
Eat more coarse grains and vegetables for dietary fiber, drink 1.5-2L of water daily, walk after meals, and toilet regularly without squatting long; soak in warm water for haemorrhoids. Iron supplements can worsen constipation — discuss an adjustment with your doctor; in serious cases choose a pregnancy-safe medication rather than a stimulant laxative.
What about lower-back pain at week 30?
It comes from a forward centre of gravity and ligament relaxation. Avoid long standing or sitting, wear supportive low-heeled shoes, use a belly-support belt, side-sleep with a pregnancy pillow, do prenatal yoga and pelvic-floor exercise, and apply local warmth. Sharp pain on one side or with bleeding and fever needs care.
What should go in the hospital bag?
It sorts into three: mum’s supplies (maternity pads, nursing bra, toiletries), baby’s supplies (NB nappies, swaddle, going-home outfit), and documents (ID card, social-security card, prenatal records). Prepare it in batches before week 34 and keep the list by the door so you can leave at a moment’s notice.
⚡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 30 daily focus

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

Day 1Your baby can now clearly tell your voice apart from others’ — your pitch, rhythm and emotional tone are already the most familiar voice in its world. Today, facing your belly, tell it about your small daily things in the most ordinary tone: "I had red-bean porridge today" "It rained a little just now, the window’s open and it’s cool" — no need to read formally; just connect with your everyday voice. This familiarity turns into a sense of security after birth.Day 2Bloated and full after a few bites? Use the "reverse-formula" rule: split the total food of your three main meals into 5-6 small portions, stop at seven-or-eight-percent fullness (you could eat a few more bites but aren’t hungry) at each; sit or stand upright for 15 minutes after meals so the uterus doesn’t squeeze the stomach further upward; don’t eat in the 2-3 hours before bed. If bloating comes with severe acid reflux and a burning feeling when swallowing, prop your upper body up 30 degrees when sleeping.Day 3Listen to 15 minutes of soothing natural sound daily (waves, birdsong or solo piano) at no higher than 60 decibels. The point isn’t "letting the baby appreciate music to cultivate taste" — there’s no scientific evidence for that. The point is that when you relax, your body releases endorphins and lowers cortisol, helping you relax the body and mind, improve sleep and steady your mood. Play music for yourself; your baby enjoys the "knock-on benefits" of your relaxation.Day 4This week attend a hospital or online delivery-experience class (2-3 hours) covering: a 3D animation of the delivery process, Lamaze breathing practice, delivery-position choices and birthing-ball use, the mechanism and timing of epidural analgesia, and the division of roles for dad in the labour ward. Bring a pen and notebook for key information and go with dad — he needs to know the labour ward isn’t "a place to wait and hold the baby".Day 5Amniotic-fluid volume is near its pregnancy peak this week (about 800-1000ml), declining gradually after weeks 32-34. Your baby’s urine is the main source of amniotic-fluid circulation, and the volume is an important window on placental function and fetal health. If the small scan finds low or high amniotic fluid, the doctor will advise drinking more water and monitoring more often — don’t "down water" on your own; follow the obstetric guidance.Day 6Tell true "broken waters" from "leaking urine": broken waters is an uncontrollable continuous flow of clear or slightly yellow fluid that you can’t stop even by clenching the perineal muscles; leaking urine is a small spray when you cough or laugh and can be paused by contracting the perineum. If you suspect broken waters but aren’t sure — lie flat immediately, use a clean sanitary pad to observe the colour, and if it stays wet treat it as real broken waters and seek care; better to go to the hospital and find it was a false alarm than to wait at home.Day 7Small-scan day (or confirm the date): today look on the B-ultrasound screen at whether BPD (biparietal diameter), AC (abdominal circumference) and FL (femur length) are in the normal range, plus amniotic-fluid volume, placental position and umbilical blood flow. Ask the doctor three questions: "What position is the fetus in now?" "Is the placental position normal?" "Is the umbilical-blood-flow resistance value in the normal range?" — note the answers in your phone memo for comparison at the next visit.

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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