When does the second trimester start and end?

The second trimester starts at week 13 in the NHS week-by-week guide, whose second-trimester section runs to week 27. In the US, the American College of Obstetricians and Gynecologists (ACOG) counts it from 14 weeks 0 days to 27 weeks 6 days. The NHS guide's week 13 page puts it simply: you are now a third of the way through your pregnancy.

Second trimester weeks, by source
Source	Starts	Ends
NHS week-by-week guide (England)	Week 13	Week 27
ACOG (United States)	14 weeks 0 days	27 weeks 6 days
Health Service Executive, HSE (Ireland)	13 weeks	28 weeks
Pregnancy, Birth and Baby (Australia)	Week 13 or week 14 (its page gives both)	Week 26 or week 27

The one-week differences are explained in pregnancy trimesters by week. In months, the second trimester is roughly months 4 to 6.

What develops in the second trimester?

ACOG calls the second trimester "the time of rapid growth and development". Its guide to fetal growth lists, in order:

Weeks 13 to 16: bones harden, especially the long bones; hearing starts to develop; the lungs begin to form the tissue that will exchange oxygen and carbon dioxide after birth.
Weeks 17 to 20: the part of the brain that controls movement is fully formed, the digestive system is working, and soft hair called lanugo starts to cover the body.
Weeks 21 to 24: kicks and turns are stronger, the sucking reflex is developing and fat is forming under the skin.
Weeks 25 to 28: the lungs are fully formed but not yet ready to work outside the uterus, they begin to make surfactant, and the eyelids can open and close.

Pregnancy, Birth and Baby adds that by week 20 your baby can hear sounds, including your heartbeat. For more detail at a given point, see 20 weeks pregnant.

What are second trimester symptoms like?

The early sickness often lifts, and newer, more physical symptoms take its place. The HSE says the second trimester often brings renewed energy, that nausea and fatigue may be easing, and that by week 20 morning sickness should ease off for most women.

The NHS week-by-week guide lists these among the second-trimester symptoms you might notice:

swollen and bleeding gums, and nosebleeds
pains at the side of your bump from the growing womb, known as round ligament pain
headaches, bloating, constipation, indigestion and heartburn
leg cramps, feeling hot, dizziness, and swollen hands and feet
darker patches on your face (chloasma), greasier or spotty skin, and thicker, shinier hair

The HSE adds back and pelvic girdle pain, as your ligaments stretch and soften, and heavy, swollen legs and ankles, which it says may be worse in hot weather or after standing. Pregnancy, Birth and Baby says your skin may itch mildly as it stretches, you may get stretch marks and you will probably need maternity clothes.

On sleep, the HSE recommends sleeping on your side from the second trimester; Pregnancy, Birth and Baby says to start from 28 weeks.

When will you feel the baby move?

Usually during this trimester. The NHS says you should start to feel your baby move between 16 and 24 weeks, and if this is your first baby you might not feel movements until after 20 weeks. Pregnancy, Birth and Baby puts it at about week 19, or sooner if this is not your first pregnancy. The NHS describes early movements as a gentle swirling or fluttering.

If you have not felt your baby move by 24 weeks, the NHS says to tell your midwife, who will check the heartbeat and movements. When do you feel the baby move covers what affects the timing, including an anterior placenta.

Appointments, scans and vaccines in the second trimester

The second trimester includes the detailed 20-week scan and, for some people, a test for gestational diabetes. In England the NHS schedule is:

Second-trimester care in England (NHS)
When	What happens
16 weeks	Appointment to discuss earlier screening results, check your blood pressure and test your pee.
From 16 weeks	Whooping cough vaccine: usually given at 20 weeks, and best before 32 weeks.
18 to 21 weeks	Ultrasound scan to check your baby's development, sometimes called the 20-week screening scan.
24 to 28 weeks	Testing for gestational diabetes if you have a higher chance of it.
25 weeks	Appointment if this is your first baby: blood pressure, pee test, measuring your bump, your baby's movements and your mental health.

The NHS explains that blood pressure and urine checks, which recur at these appointments, look for high blood pressure, the pregnancy condition pre-eclampsia and urine infections. Elsewhere the timings are similar but not identical:

United States: ACOG says the quad screening blood test is done between 15 and 22 weeks, and an ultrasound exam that checks for major physical defects between 18 and 22 weeks.
Ireland: the HSE lists the whooping cough vaccine after 16 weeks, the fetal anatomy scan at 18 to 22 weeks and diabetes screening between 24 and 28 weeks.
Australia: Pregnancy, Birth and Baby says most people have visits every 4 to 6 weeks, a morphology scan at about 18 to 20 weeks and an oral glucose tolerance test at 24 to 28 weeks.

When to call your midwife or doctor

The NHS says to call your midwife or maternity unit immediately if your baby is moving less than usual, you cannot feel them moving any more, or their usual pattern of movements changes. It says: "Do not wait until the next day – call immediately, even if it's the middle of the night." Our page on reduced fetal movements explains what happens when you call.

Pregnancy, Birth and Baby says to contact your doctor, midwife or hospital immediately if you have:

vaginal pain, bleeding, or a constant, clear watery discharge
severe nausea, vomiting or tummy pain
sudden blurry vision or a severe headache, or sudden swelling of your face, fingers or ankles
a fever
regular, painful contractions before 37 weeks
severe itching

The HSE also says to talk to your GP or midwife about severe back or pelvic pain or pain when you pee, and to get medical help if swelling appears suddenly or suddenly gets worse.

Frequently asked questions

When does the second trimester start?

At week 13 in the NHS week-by-week guide and for the HSE in Ireland. In the US, ACOG starts it at 14 weeks 0 days, because it counts the first trimester up to 13 weeks and 6 days. Australia's Pregnancy, Birth and Baby gives both week 13 and week 14 on the same page.

How many weeks is the second trimester?

Fifteen weeks in the NHS guide, which runs it from week 13 to week 27. ACOG's version, from 14 weeks 0 days to 27 weeks 6 days, is 14 weeks. The HSE describes it as 13 to 28 weeks. Whichever definition you use, it covers roughly months 4 to 6 of pregnancy.

Do symptoms get better in the second trimester?

Often, but not all of them. The HSE says the second trimester often brings renewed energy, and that nausea and fatigue may ease. The NHS guide lists second-trimester symptoms that include round ligament pain, heartburn, leg cramps, bleeding gums and swollen hands and feet.

Can you still feel sick in the second trimester?

Yes, for a while. The NHS week-by-week guide lists morning sickness among the earlier symptoms you may still have at 13 weeks, and the HSE says it should ease off by week 20 for most women. Pregnancy, Birth and Baby says severe nausea or vomiting needs a call to your doctor, midwife or hospital straight away.

Second Trimester: Weeks, Symptoms, Scans and Movements