Third trimester: weeks, symptoms and tests

Weeks in this trimester

Your body

OWH lists these changes in the third trimester:^[1]

• shortness of breath;^[1]
• heartburn;^[1]
• needing to urinate often;^[1]
• trouble sleeping;^[1]
• swelling;^[1]
• hemorrhoids.^[1]

Your baby

• OWH says the baby's eyes can sense light by about week 32.^[1]
• OWH says the baby gains weight and usually turns head-down.^[1]

Visits and tests

For a healthy pregnancy, NICHD describes visits every 2 weeks from 28 to 36 weeks, then every week until birth.^[4]

OWH lists these tests:^[5]

• a nonstress test after week 28;^[5]
• a biophysical profile in the third trimester;^[5]
• a group B strep test at weeks 36 to 37.^[5]

MedlinePlus says the group B strep swab is done a few weeks before the due date.^[6] It says routine third-trimester lab tests and ultrasounds are not needed for everyone.^[6]

• Prenatal tests by week: what's offered and when

Taking care of yourself

• MedlinePlus says most people need about 450 extra calories a day in the third trimester, and often none in the final weeks.^[9]
• CDC's Yellow Book says most airlines allow flying until 36 weeks, and some limit international flights earlier.^[10]
• CDC's Yellow Book says pregnancy complications are most likely in the first and third trimesters.^[10]
• MedlinePlus says to discuss pain-relief options with your provider before the due date.^[11]
• The NHS says the safest position to go to sleep is on your side, left or right.^[12] It says research suggests that after 28 weeks, falling asleep on your back can double the risk of stillbirth.^[12]
• The NHS says to pack your hospital bag at least 3 weeks before your due date.^[13]
• The NHS says to bring a car seat for the trip home from the hospital.^[13]

Signs of labor

MedlinePlus says labor usually starts between 37 and 42 weeks.^[11] It describes three stages: the cervix opening, pushing and birth, and delivery of the placenta.^[11]

The NHS says a baby is full term at 37 weeks, and a birth then would not be considered early.^[14]

MedlinePlus lists these signs that labor is near:^[15]

• the baby dropping lower, called lightening;^[15]
• bloody show;^[15]
• the water breaking;^[15]
• diarrhea;^[15]
• an urge to get the home ready, called nesting.^[15]

MedlinePlus says true labor contractions come at regular times, get closer together and stronger, and do not stop with activity.^[15] It says Braxton Hicks contractions are irregular and do not change the cervix.^[15]

MedlinePlus says to contact your provider for:^[15]

• leaking fluid;^[15]
• less movement from the baby;^[15]
• bleeding that is more than spotting;^[15]
• regular, painful contractions every 5 to 10 minutes for 60 minutes.^[15]

MedlinePlus does not give one rule for when to go to the hospital, and says to follow your provider's instructions.^[15]

Preterm labor

MedlinePlus says labor that starts before 37 completed weeks is preterm labor.^[16]

MedlinePlus lists these signs of preterm labor:^[16]

• contractions every 10 minutes or more often;^[16]
• leaking fluid or bleeding;^[16]
• pressure in the pelvis;^[16]
• a dull backache;^[16]
• cramps like a period, or belly cramps with or without diarrhea.^[16]

Feelings check-in

The National Institute of Mental Health (NIMH) says perinatal depression covers depression during pregnancy and after birth.^[17]

HRSA says the National Maternal Mental Health Hotline, 1-833-852-6262, takes calls and texts 24/7 in English and Spanish.^[18]

• Emotions in pregnancy and after birth: where to get help
• Baby blues vs. postpartum depression: signs and help

When to call or get help

MedlinePlus says to call your provider in the third trimester for:^[6]

• bleeding, or discharge that smells bad;^[6]
• fever, chills, or pain when you urinate;^[6]
• headaches or changes in vision;^[6]
• the water breaking, or regular painful contractions;^[6]
• less movement from the baby;^[6]
• a lot of swelling, chest pain, or trouble breathing.^[6]

The NHS says you should still feel the baby move at the same rate until you give birth, and to contact your midwife or hospital as soon as possible if the pattern changes or the baby stops moving.^[19]

CDC lists the baby's movement stopping or slowing among its urgent warning signs.^[20]

• Pregnancy warning signs: when to call or get help