39 Weeks Pregnant
At 39 weeks pregnant you are officially full term — your baby is around 20 inches long, roughly 7 to 7.5 pounds, and the lungs are now fully mature and ready to breathe air. This is often called the longest week of pregnancy: your body is doing quiet prep work for labor, your cervix is softening, and there is no good way to make labor hurry. Track your baby's movements every day, and learn the signs that mean it is time to call.
Your week at a glance
| This week | Details |
|---|---|
| Baby size | About a small watermelon, roughly 20 inches and 7–7.5 pounds |
| What is developing | Lungs fully mature, fat building under the skin, sharp reflexes, antibodies from you |
| Your symptoms | Pelvic pressure, practice contractions, fatigue, mucus plug, nesting energy |
| To-do | Confirm go-time plans, learn the 5-1-1 rule, gentle walks, track movement daily |
How big is your baby at 39 weeks?
Your pregnancy is officially full term this week. ACOG defines full term as 39 weeks 0 days through 40 weeks 6 days. Your baby is around 20 inches long and roughly 7 to 7.5 pounds — about the size of a small watermelon. The lungs are now considered fully mature, with enough surfactant produced to keep the air sacs open after birth. The brain is still growing rapidly and will keep doing so for years, but it has reached the structural milestones it needs for the outside world. Reflexes are sharp, the digestive system is ready to handle milk, and the immune system has been picking up protective antibodies from you through the placenta.
You will notice fewer visible changes in size from week to week now, because most of the big development happened in the months leading up to today. What is still happening is fine-tuning. Fat continues to build under the skin, smoothing out cheeks and arms and helping with body temperature. Most of the lanugo (downy hair) and vernix (waxy white coating) have shed or thinned. Skin is pink and smooth, hair may be long, and fingernails often reach the ends of the fingers. Most babies are head-down with the chin tucked in the classic birth-ready position. Space is so tight that movements feel less like kicks and more like big rolls, stretches, and shoves. Hiccups are still common, and you should feel your baby move every day.
39 weeks pregnant symptoms
Your body is doing quiet prep work for labor. Behind the scenes, your cervix is ripening — softening, thinning (effacing), and possibly opening (dilating) a bit. These are the common things you may notice this week:
- The mucus plug coming out as a thicker, jelly-like glob, sometimes streaked with pink, brown, or red (bloody show) — this can happen days or a week or two before active labor
- Intense pelvic pressure as your baby settles deeper, with full, heavy sensations and occasional "lightning crotch" zings
- Braxton Hicks contractions that can be strong and frequent, making you wonder if this is the real thing
- Heavy fatigue, broken sleep, and vivid dreams as the waiting wears on
- Heartburn, leg cramps, and swollen ankles
- Colostrum leaking from your breasts and a sudden burst of nesting energy
The simplest way to tell practice contractions from real labor is the pattern: real labor contractions get longer, stronger, and closer together over time and do not let up. Practice contractions stay irregular and ease with a position change, water, and rest.
Taking care of yourself this week
This is a good week to give yourself permission to slow down, even if your nesting brain disagrees. Short walks help with pelvic mobility, sleep, and circulation, and may encourage your baby to settle deeper. Time on a birth ball with slow hip circles, side-lying stretches, cat-cow on hands and knees, and gentle pelvic tilts all ease pressure. Stop right away if anything feels sharp or makes you dizzy. Side-lying rest during the day, ideally on the left, takes pressure off the big veins in your belly and helps blood flow to your baby. Naps absolutely count.
- Eat light, steady, and nutrient-dense — small frequent meals work better than three big ones because your stomach has little room.
- Hydrate throughout the day — it helps with practice contractions, swelling, and energy.
- Confirm your go-time plan — make sure your partner has the provider's office, after-hours line, labor and delivery, and doula numbers.
- Charge your phone every night, keep the hospital bag by the door, and double-check the car seat is installed correctly.
- Skip herbal labor-induction remedies, including castor oil, unless your provider says yes.
On food safety, keep caffeine under about 200 mg a day, and skip unpasteurized dairy, raw sprouts, high-mercury fish (swordfish, king mackerel, tilefish, shark), deli meats unless steaming hot, and undercooked meat or eggs. Skip alcohol entirely.
Appointments & tests
Your weekly visit includes the now-familiar checks: blood pressure, a urine dip for protein and sugar, weight, fundal height (around 39 centimeters), listening to your baby's heartbeat, and feeling your belly to confirm your baby's position. Many providers offer an optional cervical exam at 39 weeks to see whether your cervix is softening, thinning, or opening. A cervix that is one or two centimeters dilated does not mean labor is imminent; a closed cervix does not mean labor is far off. These exams are optional, and you can decline.
From 39 weeks on, your provider may offer a membrane sweep. During a cervical exam, they gently sweep a finger between your cervix and the amniotic sac to release prostaglandins, which may help start labor. Research suggests it modestly reduces the chance of going past 41 weeks. It can be crampy for a day or two and sometimes causes light spotting. It does not always work and is completely optional. This is also a good visit to confirm hospital pre-registration, your insurance, and the right number to call when labor starts — and to ask when your provider wants you to head in (most use the 5-1-1 rule for a first baby).
Call your provider if
- Contractions come every 5 minutes, each lasting about a minute, for at least an hour (the 5-1-1 rule) — call sooner if you have had a baby before
- Your water breaks or you notice any leaking fluid — call right away, not in the morning; head straight in if the fluid is green, brown, or stained
- A clear decrease in your baby's movement compared to their normal pattern
- Any bleeding heavier than spotting or bloody show
- Severe or persistent headache, vision changes, sudden swelling in your face or hands, or pain in your upper right abdomen (possible preeclampsia)
Reflects Mayo Clinic and Cleveland Clinic third-trimester fetal-development references and fetal-movement (kick count) guidance, 2024–2026.
Related questions
- Does 39 weeks count as full term?
- Yes. ACOG defines full term as 39 weeks 0 days through 40 weeks 6 days. At 39 weeks your baby's lungs are considered fully mature, with enough surfactant to keep the air sacs open after birth, and the reflexes, digestive system, and immune system are ready for life outside the womb.
- How big is the baby at 39 weeks pregnant?
- Around 20 inches long and roughly 7 to 7.5 pounds — about the size of a small watermelon. Healthy babies vary a lot in size at term. Most are head-down with the chin tucked in the birth-ready position, and movements feel more like big rolls and stretches than sharp kicks because space is tight.
- What is the 5-1-1 rule for going to the hospital?
- Most US providers tell first-time parents to call when contractions come every 5 minutes, each lasting about 1 minute, for at least 1 hour. Real labor contractions get longer, stronger, and closer together and do not ease with rest, water, or a position change. If you have had a baby before, your provider may want you to call sooner. Call right away — not in the morning — for leaking fluid, bleeding heavier than spotting, or decreased baby movement.
- What is a membrane sweep at 39 weeks?
- During a cervical exam, your provider gently sweeps a finger between your cervix and the amniotic sac to release prostaglandins, which may help start labor. Research suggests it modestly reduces the chance of going past 41 weeks. It can be crampy for a day or two and sometimes causes light spotting. It does not always work and is completely optional.
Sources & further reading
ParentFlow: one free app, pregnancy to age six
ParentFlow follows your pregnancy week by week — baby size, what's developing, your symptoms, and the appointments and warning signs that matter — then becomes a free baby tracker for feeds, sleep, and growth after birth. Free on iPhone and Android.
App Store Google Play Open Web AppThis article reflects current ACOG, Mayo Clinic, Cleveland Clinic, CDC, and FDA guidance and is for educational purposes only. It does not constitute medical advice. ParentFlow is a wellness companion — not a substitute for your obstetric provider. For any medical concern, contact your healthcare provider.