The third trimester is the final stage of pregnancy. It covers the last few months leading up to labor.
We look at what a woman can expect in each week of the last trimester. We also describe the fetus’ development when to schedule doctor visits.
The third trimester starts at 28 weeks and ends with labor, which tends to occur at around 40 weeks of pregnancy.
If a pregnant woman does not go into labor by week 42, the doctor will induce it. They may do so as early as 39 weeks to ease any health risks.
Health checks are more frequent in the third trimester, and they may need to take place every 2 weeks.
The experience of pregnancy is different for everyone, but a woman can generally expect the following changes throughout the third trimester.
Week 28
The woman may have:
Also, as the body retains water, there may be a small amount of swelling in the hands and feet. Still, it is best to let a doctor know about any swelling, as it can be a sign of preeclampsia.
The fetus:
- is about 37 centimeters (cm) long
- weighs around 900 grams (g)
- can blink in response to sound
Week 29
The woman may:
- have heartburn
- notice varicose veins
- find that their bellybutton sticks out
- have a frequent need to urinate if the fetus is pressing against the bladder
- can open their eyes, focus, and respond to light inside the womb
- develops more fat under the skin, which becomes smoother and less wrinkled
Sleeping during the third trimester can be difficult. Sleeping on one side, rather than on the back, supports the fetus. Putting pillows between the legs and beneath the bump may provide extra comfort and support.
Learn more about sleeping during pregnancy.
Week 30
The woman may:
- have vivid dreams
- feel out of breath, due to the strain of carrying extra weight and the fetus pushing against the lungs
- experience itchiness as the belly expands
Mild itching around the belly is common, but if itchiness is extreme, especially at night, talk to a doctor. Severe itching can be a sign of a liver disorder that can happen from week 30 onward.
- has kidneys that are now fully developed and functioning
- has lungs that are continuing to develop
- is losing the greasy substance and fine fur covering the skin
Now might be a good time to prepare for birth and get clothes, supplies, and any equipment organized.
Week 31
The woman may experience:
- Braxton-Hicks contractions, which should be pain-free and irregular
- a loss of coordination and balance
The fetus starts:
- practicing sucking, preparing to feed
- putting on more weight, around 200 g each week
Women tend to notice a pattern of movements at around this time. If the fetus’ movements significantly change or lessen, see a doctor or midwife.
A doctor or midwife may also measure the womb at week 31, particularly if this is the woman’s first pregnancy.
They will also check whether the fetus is in the right position for a head-first delivery. If the fetus is feet-first, there is still time for the position to change.
Keeping active throughout pregnancy may help reduce labor time and lower the risk of complications.
Week 32
- waddle, to help the body stay balanced
- gain roughly 1 pound (lb) a week over the next 4 weeks
- growing fingernails, which may be surprisingly long by birth
- increased hearing sensitivity
If people talk to the fetus at this stage, it may recognize their voices after birth. Learn more about when a fetus can hear.
Week 33
The woman may experience:
- a heavy feeling in the pelvis
- difficulty sleeping
- fatigue
The fetus:
- is roughly 43.7 cm long
- weighs around 4.2 lb
- has a fully developed brain and nervous system
In addition, all the fetus’ bones are hardening, except those in the skull.
Now might be a good time to prepare a bag for labor, in case it happens earlier than expected. It is also important to have a securely fit car seat.
Week 34
The woman may experience:
- an easing of symptoms such as heartburn and breathlessness, as the fetus gets into position for delivery
- a frequent need to urinate
- difficulty walking
- enlarged breasts
- mild leaking of breastmilk
The fetus:
- is about 45 cm long
- weighs around 4.6 lb
- may begin to dream
- may begin to move downward into the delivery position
Week 35
The woman may experience:
- vivid dreams or nightmares, which can be a normal way of dealing with anxiety or concerns
- sore ribs, due to kicks from the fetus
Medically, vivid or frightening dreams are nothing to worry about, but if they create more anxiety, let the doctor or midwife know.
It is also important to talk to a healthcare provider about severe rib pain or pressure in the chest, which can be signs of preeclampsia.
- extra fat develops to help regulate temperature during and after birth
- the testicles drop from the abdomen to the scrotum, in males
Week 36
The woman may notice:
- “nesting” behavior, which may involve cleaning or organizing the home
- the pelvic floor muscles relaxing, which can cause urine to leak
- breathe outside the womb
- suck in milk and digest it fully
Antenatal appointments are essential at this stage to ensure that the pregnancy is progressing correctly. The doctor or midwife will check blood pressure, urine, and bump size.
Depending on the position of the fetus, the doctor or midwife may apply gentle pressure to move it manually.
Week 37
The woman may experience:
- an increase in vaginal discharge
- piles, itchy or painful areas of swelling in the anus or rectum
The fetus:
- is about 48.6 cm long
- weighs around 6.4 lb
- is now “full-term” and could survive outside of the womb in the case of an early delivery
- may still be feet-first and may not change position until labor begins
If a woman has twins, they will likely be delivered in week 37. If labor has not begun by week 38, the doctor will induce it.
Week 38
The woman may experience:
- feelings of frustration or boredom
- colostrum, nutrient-rich milk, leaking from the breasts and leaving wet, yellow spots on clothes
The fetus:
- is about 49.8 cm long
- weighs just over 6.6 pounds
- should keep moving — talk to a healthcare provider if this changes
During this week, the doctor or midwife will likely want to check on the position of the fetus.
Week 39
A woman may go into labor during this week. Most women go into labor about a week before or after their due date.
The woman may experience:
- white vaginal discharge
- a plug of mucus mixed with blood that comes from the vagina, known as bloody show, a sign the body is ready for labor
- strong Braxton-Hicks contractions
Contact the doctor if there is any bleeding from the vagina that is not related to the mucus plug.
The fetus:
- is about 50.7 cm long
- weighs around 7.3 lb
- has thicker, tougher skin
Week 40
Many women go into labor during this week. If it does not happen, a woman may have mixed emotions, including frustration and concern, about the wait.
The fetus:
- may weigh up to 8.8 lb
- should continue to move, following a consistent pattern
There will be an antenatal appointment in week 40 and the following week if labor has not occurred.
The third trimester is the final stage of pregnancy. It lasts from week 28 to labor, which tends to occur at around week 40. However, some women deliver earlier or later than this.
The third trimester can cause uncomfortable physical changes. If any are severe, contact a healthcare provider right away.
Attending all antenatal appointments during the third trimester is key — it helps ensure a safe pregnancy and delivery.