The second trimester is the middle stretch of pregnancy. The NHS counts it as weeks 13 to 27. As it begins, nausea and tiredness often ease and your bump starts to show, and somewhere between 16 and 24 weeks you'll probably feel your baby move for the first time.
It's also a busy time for care. You'll be offered a detailed ultrasound at around 18 to 20 weeks, a glucose test for gestational diabetes at 24 to 28 weeks in many cases, and vaccines that help protect your baby after birth. It's a good time to start pelvic floor exercises and to begin planning for the birth. A few signs need a call to your maternity unit straight away; they're listed under "When to get help" below.
When is the second trimester?
The NHS week-by-week guide counts weeks 13 to 27 as the second trimester, with the third starting at week 28. Australia's Pregnancy, Birth and Baby page on the second trimester calls it the middle 3 months from about week 13, and its third trimester page says the third trimester begins at week 27. The labels matter less than the timing of each check.
| Weeks | What usually happens |
|---|---|
| 13 | Second trimester starts (NHS) |
| 16 to 24 | First movements felt |
| 16 to 36 | Whooping cough vaccine (window varies by country) |
| 18 to 22 | Morphology or anomaly scan |
| 20 onwards | Pre-eclampsia becomes more likely |
| 24 to 28 | Glucose test for gestational diabetes |
| 28 | RSV vaccine window opens (Australia, UK); side-sleeping starts |
Pregnancy, Birth and Baby says check-ups are usually every 4 to 6 weeks in the second trimester. The NHS antenatal appointments page lists appointments at 16 weeks, 18 to 21 weeks (the scan), 25 weeks for a first baby, and 28 weeks. At these visits your blood pressure and urine are checked and, from about 25 weeks, your bump is measured.
What symptoms change in the second trimester?
The NHS week 13 page says you're "hopefully through the worst" of your early symptoms, and needing to pee should ease as the womb moves up away from your bladder. Pregnancy, Birth and Baby says nausea will probably settle and you may feel you have more energy.
New or ongoing changes the NHS lists include:
- constipation, heartburn and indigestion
- nosebleeds and bleeding gums
- headaches, leg cramps and dizziness
- swollen hands and feet, and feeling hot
- round ligament pains (aches as the ligaments supporting your womb stretch)
- more vaginal discharge, greasier skin and thicker hair.
Pregnancy, Birth and Baby adds that stretching skin over your belly and breasts can itch mildly, and stretch marks may appear. Mild itching is common, but severe itching is one of its reasons to call your midwife or doctor straight away.
Keep moving if you can. Pregnancy, Birth and Baby suggests walking, swimming, yoga and resistance exercise, and avoiding high-impact activity or anything with a risk of falling or overheating. The NHS exercise page says to avoid activities that keep you flat on your back for more than a few minutes in later pregnancy, and ACOG explains that lying on your back lets the uterus press on a large vein.
When will I feel my baby move?
The NHS page on your baby's movements says most people start to feel movements between 16 and 24 weeks, and a first baby may not be felt until after 20 weeks. Early movements feel like a gentle swirling or fluttering. Pregnancy, Birth and Baby says you may notice them by about week 19, or sooner if you've been pregnant before, and later your partner may be able to feel kicks too.
If you haven't felt your baby move by 24 weeks, tell your midwife so they can check your baby's heartbeat. Once you know your baby's pattern, any slowing or change is a reason to call your maternity unit straight away, day or night. The NHS says not to count kicks to a set number or use a home doppler. Our guide to baby movements in pregnancy covers what's normal and what to do.
What happens at the 18 to 20 week scan?
This detailed ultrasound looks at how your baby is growing and developing. The name and timing differ a little by country:
| Region | Name | Usual timing |
|---|---|---|
| Australia | Morphology scan | 18 to 20 weeks (up to 22 in some lists) |
| UK | 20-week (anomaly) scan | 18 to 21 weeks, sometimes up to 23 |
| US | Anatomy ultrasound | 18 to 22 weeks |
- Australia. Pregnancy, Birth and Baby's morphology scan page says it's usually done at 18 to 20 weeks and is covered by Medicare, though there may be out-of-pocket costs. The second trimester page says it checks your baby's growth and body, the position of the placenta, the amount of fluid and the length of your cervix. Australia's healthdirect list of routine antenatal tests gives 18 to 22 weeks.
- UK. The NHS 20-week scan page says the scan looks for 11 conditions, including spina bifida, cleft lip and serious heart problems, and usually takes around 30 minutes.
- US. ACOG says an ultrasound at 18 to 22 weeks checks for major physical differences in the brain and spine, face, abdomen, heart and limbs.
All three sources say the scan is your choice. If something is found, the NHS says you'll be referred to a specialist and may be offered more tests. Bringing someone with you can help.
When is the glucose tolerance test?
Gestational diabetes means higher-than-usual blood sugar that develops in pregnancy. Pregnancy, Birth and Baby's gestational diabetes page says around 1 in 10 pregnancies are affected.
| Region | Who is tested | When |
|---|---|---|
| Australia | Recommended for all pregnancies | 24 to 28 weeks; earlier if higher risk |
| UK | People with risk factors | 24 to 28 weeks; earlier if you've had it before |
| US | All pregnant women screened | 24 to 28 weeks; earlier if higher risk |
- Australia. Pregnancy, Birth and Baby says an oral glucose tolerance test (OGTT) is recommended between 24 and 28 weeks in all pregnancies, with an earlier test before 20 weeks for some. You fast for 8 to 10 hours, have a blood test, drink a glucose drink, then have more blood tests after 1 and 2 hours. It says testing is your choice.
- UK. The NHS gestational diabetes page says screening is offered if you have a risk factor, such as a BMI above 30, a parent or sibling with diabetes, gestational diabetes before, or a south Asian, Black, African-Caribbean or Middle Eastern background.
- US. ACOG says all pregnant women should be screened, early if they have risk factors and otherwise at 24 to 28 weeks.
Which vaccines are offered in pregnancy?
Vaccines in pregnancy pass antibodies to your baby, protecting them in the first months before their own vaccines start working. Timing differs by country, so follow the advice where you live.
| Vaccine | Australia | UK | US |
|---|---|---|---|
| Whooping cough | 20 to 32 weeks, usually at 28 | From 16 weeks, usually around 20 | 27 to 36 weeks |
| Flu | Any time in pregnancy | Any stage, in autumn or winter | Any trimester |
| RSV | 28 to 36 weeks, usually at 28 | From 28 weeks, up until labor | 32 to 36 weeks, September to January |
- Australia. The timings come from NSW Health in Australia, which lists all three as free, although some providers charge a small fee to give them. It says that if you missed whooping cough in pregnancy, you should have it before leaving hospital, and that some babies may need an RSV antibody injection (nirsevimab) if the mother wasn't vaccinated.
- UK. The NHS whooping cough vaccine page says to have it in each pregnancy, ideally before 32 weeks for the best protection. The NHS RSV vaccine page says it's offered around your 28-week appointment in every pregnancy, can be given up until you go into labor, and helps protect your baby for their first 6 months. The NHS flu vaccine page says you can have it at any stage of pregnancy.
- US. The CDC's Tdap page recommends whooping cough vaccine at 27 to 36 weeks in every pregnancy, preferably early in that window. The CDC's RSV page recommends either the maternal vaccine at 32 to 36 weeks from September to January, or an antibody injection for the baby, and says most babies don't need both. The CDC's flu page recommends a flu shot in any trimester, not the nasal spray.
For your baby's own schedule after birth, see baby vaccinations.
Why start pelvic floor exercises now?
Your pelvic floor supports your bladder, uterus and bowel, and it carries extra weight as your baby grows. Pregnancy, Birth and Baby's pelvic floor page says training before, during and after pregnancy may help prevent or reduce problems such as leaking. Continence Health Australia says leaking is common but not normal, and help is available.
- Find the muscles. Sit or lie with your thighs, buttocks and tummy relaxed. Squeeze as if you're trying to stop passing wind.
- Squeeze and lift. You should feel the muscles around your back passage and vagina lift up inside, while you keep breathing normally.
- Hold, then fully relax. Over time, hold the squeeze harder and for longer before letting go.
- Make it daily. Pregnancy, Birth and Baby suggests linking it to something you do every day, like waiting for the kettle.
- Squeeze before you cough, sneeze or lift.
If you can't feel the muscles working, or you're already leaking, ask your doctor or midwife about a pelvic floor physiotherapist or continence nurse.
What should I start planning?
- Antenatal classes. Pregnancy, Birth and Baby suggests asking your midwife or doctor what's available and going with your birth partner. The NHS says classes are worth it even if you've had a baby before.
- Your birth preferences. It's a good time to start thinking about where you'd like to give birth and what matters to you. See our birth plan guide.
- Work and leave. Pregnancy, Birth and Baby suggests talking with your partner and employer about when you'll start leave and how you'll share care.
- Side-sleeping from 28 weeks. Pregnancy, Birth and Baby says to start going to sleep on your side from 28 weeks. Our guide to sleep positions in pregnancy explains why and how.
When to get help
The NHS bleeding in pregnancy page says to call an ambulance if you're bleeding and have severe tummy pain, feel faint or dizzy, or the bleeding is heavy.
Call your maternity unit, midwife or doctor now, day or night, if you have:
- any vaginal bleeding, vaginal pain, or tummy pain that worries you
- a gush or constant trickle of clear, watery fluid
- regular, painful contractions or tightenings before 37 weeks
- a change in your baby's movements, once you've started to feel them
- signs of pre-eclampsia: a severe headache that doesn't go away with simple painkillers, vision problems such as blurring or flashing lights, pain below the ribs, or sudden swelling of your face, hands or feet
- a fever, severe vomiting, or severe itching.
This list follows Pregnancy, Birth and Baby's second trimester page, which says to contact your midwife, doctor or hospital immediately. The NHS pre-eclampsia page says it's most likely from 20 weeks, and to call your maternity unit if you have symptoms. Pregnancy, Birth and Baby's pre-eclampsia page adds that most people have no symptoms, which is why your blood pressure is checked at every visit. If you can't get through, go to your hospital.
Tell your midwife soon if you haven't felt your baby move by 24 weeks, or you're leaking urine.
Feeling anxious about the birth or about becoming a parent is common. Pregnancy, Birth and Baby says that if these feelings start to affect your wellbeing, it can be a sign of antenatal depression or anxiety, so talk to your midwife or doctor. You can also contact the National Maternal Mental Health Hotline on 1-833-852-6262 (call or text). If you have thoughts of harming yourself, call 988 (call or text) or 911 now. See postnatal mood for more.
What's useful to note down?
A short pregnancy diary can help: when you first felt movements and when your baby tends to be busy, your vaccine dates, and your scan and glucose test results. Write down questions as they come up, so you can ask them at your next appointment. When you reach 28 weeks, read the third trimester guide.
