Week 38 · Third trimester
Week 38 fetal development and pregnancy guide — length about 49.8cm, weight 约3083g (about the size of a 小冬瓜)
Your baby is now about 49.8cm and 约3083g, about the size of a 小冬瓜.
Medical references: WHO INTERGROWTH-21st · China Prenatal & Pregnancy Care Guide · ACOG
View each day of week 38 →Week 38 fetal development milestones: length / weight / ultrasound data
Key developmental changes during week 38:
- The brain and nervous system keep maturing (only basically complete around 2 years after birth).
- Most of the lanugo (fine body hair) falls off, though some babies still carry a little at birth.
- Pulmonary surfactant is fully in place and breathing is ready.
- The grasp and sucking reflexes are very skilled.
- Subcutaneous fat is ample and the body is plump and full.
- All systems are mature and can work independently.
- Hearing is highly mature; familiar parental and family voices evoke a reassuring sense of calm.
- Fetal-movement amplitude falls as space shrinks, but the count stays.
- The nails may be long and need trimming soon after birth.
- Meconium accumulates in the bowel and is passed in the first stool after birth.
- The immune system receives large amounts of maternal antibodies (IgG) for protection after birth.
- The baby has a clear sleep-wake rhythm, and the day-night difference in activity can be seen on ultrasound.
BPD (biparietal diameter)91.1mmWidth across the head; reflects brain development
AC (abdominal circumference)335.9mmAbdomen circumference; reflects nutrient absorption
FL (femur length)69.7mmThigh bone length; tracks gestational age
* Values are medians from WHO/China standards; individual variation is normal. References: WHO INTERGROWTH-21st, China Prenatal & Pregnancy Care Guide, ACOG guidelines.
Week 38 daily development
Your baby quietly grows every day of week 38. Tap any day to see fetal development, maternal changes, and daily guidance for that day.
260Day 1Do no lists today and check no items — find the sunniest hour of afternoon, sit in your usual sofa corner, turn off the phone, and rest both hands quietly on the highest point of the bump for 15 minutes. No need to speak, record or photograph — purely feel every turn, every push against your hand, every subtle vibration from its heartbeats within you. This is the last "together time"; soon it will be an independent person in your arms, no longer a secret inside the belly.261Day 2If some night you wake with insomnia and anxiety — "will something go wrong" "what if I can’t hold on" — these are the most normal thoughts of late pregnancy. Go to the kitchen, warm half a cup of milk, stir in a small handful of oats into porridge, and eat slowly in dim light, in no hurry. Then return to bed, side-sleep with the pregnancy pillow and do three rounds of deep breathing. The loneliness of the deep night usually lightens in morning light; what you need is not to make any major decisions at three in the morning.262Day 3Dad-to-be, remember — your most important role in the labour room is not "checking whether these items are all here" (she has checked that list 100 times) but being by her side. When contractions come she needs to hear your voice, feel your hand in her palm, know you can call the nurse for her, read the breathing rhythm to her and wipe the sweat from her forehead. You don’t need to be a medical expert — you are the one person she chose to accompany her in the labour room, and that alone is the strongest comfort.263Day 4If the due date passes and the baby hasn’t started — completely normal. Only about 5% of women give birth exactly on the due date; most start between weeks 38-42. After the due date, appointments may add ultrasound checks of amniotic-fluid volume, placental maturity and more frequent NST. Keep counting fetal movements at home without slackening — if movement is regular, the NST reactive and the fluid normal, the baby spending a few more days inside is usually fine; wait patiently for your body’s own signal.264Day 5Today check whether the home already creates the newborn’s first environment: is the room temperature kept at 22-24°C (buy a thermometer-hygrometer and stick it on the wall by the baby’s bed), are there blackout curtains on the windows (newborns need the "light by day, dark at night" rhythm guide), and any strongly scented perfume or air freshener in the room (a newborn’s smell sense is sensitive). The home needn’t be a show home — safe, warm and quiet is the first environment a baby needs.265Day 6This week confirm delivery mode one final time with your obstetrician — if all conditions support a vaginal birth (head-down position, pelvic measurement allows a trial, moderate fetal weight, no cord-around-neck risk, normal placental position), a vaginal birth is the preferred path. If the doctor advises a cesarean for medical indications (breech, placenta praevia, macrosomia, repeated scarred uterus, etc.), understand the risks and recovery of surgery before deciding. Whichever way, safely bringing the baby into the world is the first goal.266Day 7For mums with a breech or transverse baby — if the position still hasn’t turned at week 38, this week the doctor will discuss the elective-cesarean date (around week 39) with you. The space to turn inside the uterus is now extremely limited, and the chance of natural turning drops greatly. Don’t blame yourself for "not being able to have a vaginal birth" — the position isn’t in your control, and a cesarean is an equally respectable, no less great way to give birth.
Week 38 belly changes
At week 38 (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 38 maternal body changes and common symptoms
- Psychologically you may be anxious or expectant — both are normal; no need to force "composure".
- Weight holds around 12-16kg cumulative (may plateau or dip slightly at term).
- The body may already be issuing labour-preparation signals (irregular contractions, bloody show, lightening).
- Bloating, heartburn and constipation have mostly eased; if still marked, eat small frequent meals and add fiber.
- Lower-limb swelling, cramps and varicose veins continue; adequate calcium/magnesium and raising the legs help.
- Sleep difficulty and back or pubic-bone pain are clearer as the body load peaks; heat packs and prenatal yoga help.
- Itchy abdominal skin, stretch marks and urine leaking, with frequent false contractions needing true/false distinction.
- The breasts enlarge and colostrum is secreted; breastfeeding preparation can begin.
Week 38 nutrition advice and recommended recipes
Pre-labour, focus on mood and sleep: tryptophan helps make serotonin, regulating mood and sleep — eat banana, milk, turkey, nuts and oats. A small handful of walnuts plus a carton of yoghurt daily also steadies mood. Daily targets still follow authority guidance: quality protein about 80-90g, iron about 27-29mg, calcium 1000mg, DHA 200-300mg, fiber 25-30g, iodine 230μg. Avoid alcohol, raw or unpasteurised milk products, high-mercury fish, caffeine ≤200mg a day.
DHA200-300mgBrain & vision development
Recommended recipeWarm oat porridge with milk
Milk’s tryptophan plus oats’ complex carbs — warm and sleep-promoting, soothing pre-labour tension; a small bowl before bed is just right. If lactose-intolerant, swap to sugar-free soy milk; GDM mums control the oatmeal amount and sugar.
Week 38 prenatal education guide
The core of "fetal education" is still to help the mother-to-be relax and go with the flow; there is no strong evidence that any specific stimulation makes the baby smarter. This week you can put down the "techniques" and return to the most primal mother-baby bond: sit quietly, place your hands on the belly, focus on feeling each of the baby’s movements — simply feeling, demanding nothing — this is itself a fine relaxation and parent-child bond that helps you calmly await the baby’s arrival.
Week 38 partner's role
①Be psychologically ready to leave at any time, and re-confirm all contacts and transport to hospital. ②Most important: stay calm and be present — what Mum needs most in the labour room is "you are here"; presence alone is the strongest comfort. ③Learn the labour-support process (epidural, perineal massage, birthing ball, breathing guidance). ④Talk or sing close to the belly at a set time daily to build a father’s voice the baby recognises.
Week 38 checkup reminders
Week 38: weekly prenatal visit + NST fetal-heart monitoring. If a breech or transverse position hasn’t turned, the elective-cesarean date may be set this week. Keep counting fetal movements daily. Learn the labour signals (bloody show, rupture of membranes, regular 511 contractions) and seek care as they appear.
Week 38 key concerns
Signs that need immediate care at week 38
If any of the following occurs, contact your obstetrician or seek medical help promptly: ① no fetal movement felt for over 12 hours → seek care immediately; ② any severe headache, blurred vision or severe upper-abdominal pain with raised blood pressure or sudden oedema (watch for preeclampsia); ③ rupture of membranes → lie flat immediately with hips raised and seek care; ④ regular contractions (the 511 rule) → go to hospital; ⑤ clearly reduced fetal movement (fewer than 10 in 2 hours or less than half the usual); ⑥ itching all over, especially the palms and soles with no rash (watch for ICP); ⑦ a fever over 38℃ that does not come down; ⑧ one leg swollen, hot and painful, or sudden breathlessness and chest pain (watch for a clot/pulmonary embolism).
Week 38 frequently asked questions
Past the due date but not in labour?
Normal — only about 5% of babies are born exactly on the due date; 40-41 weeks are both within the full-term normal range. Strengthen fetal-movement monitoring and attend weekly visits + NST; no need to be anxious.
Week 38 — vaginal birth or induction?
Without a medical indication, await natural onset. Week 38 is early term; it is generally more ideal to wait until after 39 weeks; if there is a medical indication (GDM, hypertension, placental factors), the doctor arranges induction or elective cesarean at 39-41 weeks. Breech, transverse or fetal distress follow the doctor’s guidance.
How much weight gain is normal at week 38?
A cumulative gain of about 12-16kg by week 38 is common. Weight may plateau or dip a little at term — normal; the recommended total gain is about 11.5-16kg (standard BMI), so watch the overall trend.
How to read the week-38 ultrasound report?
The three measurements at 38 weeks: BPD (biparietal diameter) about 91.1mm, AC (abdominal circumference) about 335.9mm, and FL (femur length) about 69.7mm. 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 fetal movement regular at week 38?
At term, space shrinks and amplitude may ease slightly, but the count should not clearly drop. Since week 28 count daily: one hour morning, noon and evening, with ≥10 in 2 hours normal; if clearly under 10 in 2 hours or less than half the usual, seek care immediately.
What labour signals does the body give at week 38?
Common signals: stronger irregular contractions, bloody show (mucus plug passing) and lightening (easier breathing, worse urination). The true signs of labour are regular contractions (511) or rupture of membranes — seek care promptly.
Has the lanugo fallen off at week 38?
By week 38 most lanugo (fine body hair) has fallen off, but some babies still have a little on the shoulders and back at birth — normal, and it fades over the weeks after birth. Nothing to worry about.
Is there a recommended exercise duration in pregnancy?
ACOG recommends about 150 minutes of moderate-intensity exercise accumulated weekly. Week 38 is still early term; favour walking, stretching and prenatal yoga, avoiding intense exercise and pressure on the abdomen; seek care immediately if regular contractions, rupture of membranes, bleeding or clearly reduced movement occur. Generally it’s more ideal to wait until after 39 weeks before considering induction.
Do I still need vaccinations at week 38?
The CDC and ACOG recommend the Tdap (pertussis) vaccine at weeks 27-36; this week is past the window, so if not yet given, ask your doctor whether a catch-up is possible. The inactivated flu vaccine can also be given in flu season.
Can I have sex at week 38?
After term, sex may trigger contractions and is generally advised against. With no contraindications and the doctor’s permission, very gentle sex could be acceptable, but most doctors advise pausing; see a doctor immediately for bleeding, pain or fluid leakage after sex.
What about leg cramps and oedema at week 38?
For a cramp, flex the foot and massage the calf; prevention centres on calcium, magnesium, water and stretching before bed. Continued oedema and cramps: raise the legs, lie on your left side, walk to promote return flow and limit salt; if the swelling suddenly worsens, spreads to the face and hands or comes with headache/vision changes, check blood pressure to rule out preeclampsia.
What should I avoid eating at week 38?
Still avoid raw or undercooked meat, fish and eggs, high-mercury large fish, unpasteurised dairy, alcohol, caffeine up to 200mg a day, and excess animal liver. GDM mums strictly control refined sugar; don’t try castor oil or other "labour-inducing" foods because you want to start — the risk outweighs the benefit, and induction is done properly in hospital.
What about heartburn and bloating at week 38?
At term the stomach space frees up and heartburn mostly eases, but one overfull meal still brings reflux. Eat small frequent meals, chew slowly, stay sitting 30 minutes after a meal before lying down, don’t eat within 2-3 hours before bed, avoid spicy, greasy, overly sweet food and fizzy drinks, and prop up the upper body; in severe cases use a pregnancy-safe antacid as directed.
What about constipation and haemorrhoids at week 38?
Eat more coarse grains, fruit and vegetables for fiber, drink 1.5-2L of water daily, walk after meals and toilet on a regular schedule without squatting long; warm-water sitz baths help. Iron supplements can worsen constipation — discuss adjusting them with your doctor; choose a pregnancy-safe medication for severe constipation and avoid stimulating laxatives.
What about lower-back and pubic-bone pain at week 38?
At term, forward centre of gravity and relaxin loosening the pelvic joints bring back/pubic pain to its peak. Avoid long standing or sitting, wear supportive low shoes, use a belly-support belt, side-sleep with a pregnancy pillow, do prenatal yoga and pelvic-floor exercises and apply local heat; sharp pain on one side, or with bleeding or fever, needs medical care.
Can’t sleep well and anxious at week 38?
Pre-labour anxiety and insomnia are common. Use a pregnancy pillow for support, side-sleep, soak your feet before bed, drink warm-milk oats and walk moderately in the day; clarifying labour preparations and induction timing with your doctor raises your sense of security; if anxiety is marked, talk to the doctor and an NST confirming all is well reassures you.
Are frequent false contractions at week 38 normal?
Frequent false contractions at term are fairly common: brief tightening, painless, irregular, resolving with rest. If they become regular, painful or come with lumbar heaviness (meeting 511), seek care to rule out the onset of labour.
What should the hospital bag contain?
Three categories: maternal items (postnatal pads, nursing bra, toiletries, straw cup), baby items (NB nappies, swaddling, going-home clothes, small hat) and documents (ID, social-security card, prenatal record). By week 38 it should be packed and at the door, ready to go; if a scheduled cesarean for breech, re-check it against the surgery date.
What head size/biparietal diameter is normal at week 38?
At 38 weeks a BPD (biparietal diameter) of about 91.1mm is the median (head diameter about 9cm+). Judge together with the abdominal circumference, femur length and your obstetrician’s overall assessment; a single slight deviation isn’t necessarily abnormal.
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
- Guidelines for Pre-conception and Prenatal Care (Chinese Society of Obstetrics and Gynecology)
- ACOG Methods for Estimating the Due Date (Committee Opinion No.700)
- WHO INTERGROWTH-21st fetal growth standards
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 38 daily focus
Key daily tips for this week; tap any item to view the full development and guidance for that day.
Day 1Do no lists today and check no items — find the sunniest hour of afternoon, sit in your usual sofa corner, turn off the phone, and rest both hands quietly on the highest point of the bump for 15 minutes. No need to speak, record or photograph — purely feel every turn, every push against your hand, every subtle vibration from its heartbeats within you. This is the last "together time"; soon it will be an independent person in your arms, no longer a secret inside the belly.Day 2If some night you wake with insomnia and anxiety — "will something go wrong" "what if I can’t hold on" — these are the most normal thoughts of late pregnancy. Go to the kitchen, warm half a cup of milk, stir in a small handful of oats into porridge, and eat slowly in dim light, in no hurry. Then return to bed, side-sleep with the pregnancy pillow and do three rounds of deep breathing. The loneliness of the deep night usually lightens in morning light; what you need is not to make any major decisions at three in the morning.Day 3Dad-to-be, remember — your most important role in the labour room is not "checking whether these items are all here" (she has checked that list 100 times) but being by her side. When contractions come she needs to hear your voice, feel your hand in her palm, know you can call the nurse for her, read the breathing rhythm to her and wipe the sweat from her forehead. You don’t need to be a medical expert — you are the one person she chose to accompany her in the labour room, and that alone is the strongest comfort.Day 4If the due date passes and the baby hasn’t started — completely normal. Only about 5% of women give birth exactly on the due date; most start between weeks 38-42. After the due date, appointments may add ultrasound checks of amniotic-fluid volume, placental maturity and more frequent NST. Keep counting fetal movements at home without slackening — if movement is regular, the NST reactive and the fluid normal, the baby spending a few more days inside is usually fine; wait patiently for your body’s own signal.Day 5Today check whether the home already creates the newborn’s first environment: is the room temperature kept at 22-24°C (buy a thermometer-hygrometer and stick it on the wall by the baby’s bed), are there blackout curtains on the windows (newborns need the "light by day, dark at night" rhythm guide), and any strongly scented perfume or air freshener in the room (a newborn’s smell sense is sensitive). The home needn’t be a show home — safe, warm and quiet is the first environment a baby needs.Day 6This week confirm delivery mode one final time with your obstetrician — if all conditions support a vaginal birth (head-down position, pelvic measurement allows a trial, moderate fetal weight, no cord-around-neck risk, normal placental position), a vaginal birth is the preferred path. If the doctor advises a cesarean for medical indications (breech, placenta praevia, macrosomia, repeated scarred uterus, etc.), understand the risks and recovery of surgery before deciding. Whichever way, safely bringing the baby into the world is the first goal.Day 7For mums with a breech or transverse baby — if the position still hasn’t turned at week 38, this week the doctor will discuss the elective-cesarean date (around week 39) with you. The space to turn inside the uterus is now extremely limited, and the chance of natural turning drops greatly. Don’t blame yourself for "not being able to have a vaginal birth" — the position isn’t in your control, and a cesarean is an equally respectable, no less great way to give birth.
Content sources & notes
This guide references WHO INTERGROWTH-21st standards, the China Prenatal & Pregnancy Care Guide, ACOG clinical guidelines and BabyCenter (medically reviewed).
View the full fetal BPD/AC/FL reference table (weeks 14–42) →