The first trimester covers roughly the first 3 months of pregnancy, from the first day of your last period to the end of week 12. Many people feel sick, very tired and emotional in these weeks, often before anyone else knows they're pregnant. It's also when the important early jobs happen: taking folic acid (and iodine in Australia), adjusting what you eat and drink, booking your first appointment, and deciding which screening tests you want.
Most of what you feel is a normal response to pregnancy hormones. A few signs aren't, and they're covered under "When to get help" below: bleeding, tummy pain, being unable to keep fluids down, or feeling faint all mean calling someone today, and some mean calling 999.
When does the first trimester start and end?
Australia's Pregnancy, Birth and Baby page on the first trimester says it's counted from the first day of your last period through to week 12, because the date of conception often isn't known. So in the first couple of weeks of "pregnancy", you haven't conceived yet. The NHS week-by-week guide also ends the first trimester at week 12 and starts the second at week 13.
| Weeks | What usually happens |
|---|---|
| Around 4 | Early symptoms may start, or none at all |
| 4 to 10 | Morning sickness usually begins |
| 8 to 12 | NHS booking appointment with a midwife |
| From 10 | NIPT is possible |
| 10 to 14 | Dating scan and combined screening |
| 12 | NHS folic acid advice runs to at least this week |
By the end of the first trimester, Pregnancy, Birth and Baby says your baby's heart is starting to beat.
What symptoms are common in the first trimester?
The NHS week 4 page lists nausea, tiredness, sore breasts, needing to wee more often and a metallic taste in your mouth, and says some people have no symptoms at first. Pregnancy, Birth and Baby adds:
- Breast changes. Breasts often become tender, larger and heavier.
- Weeing more. Your growing uterus presses on your bladder.
- Appetite changes. Cravings, aversions, or no change at all.
- Mood swings. Hormones can make you moody or irritable, and tiredness is common in the early months.
Easing nausea
The NHS morning sickness page says it can happen at any time of day and usually clears up by 16 to 20 weeks. Pregnancy, Birth and Baby's morning sickness page says it's most likely between weeks 6 and 14. Things both suggest:
- Eat little and often. Small, frequent meals of plain, high-carbohydrate, low-fat food; a plain cracker soon after waking.
- Sip fluids little and often through the day.
- Choose cold foods if cooking smells set you off.
- Rest. Nausea can be worse when you're overtired.
- Try ginger or wristbands. The NHS suggests checking with a pharmacist before taking ginger supplements.
If it's still hard to cope, your midwife or doctor may suggest anti-sickness medicine. Check with them or a pharmacist before taking any medicine or supplement in pregnancy.
When is morning sickness more serious?
Hyperemesis gravidarum (HG) is severe, persistent nausea and vomiting that makes it hard to eat and drink enough. Pregnancy, Birth and Baby's HG page says it can lead to dehydration, weight loss, anxiety and depression, and that many people with HG need fluids through a drip in hospital at some point.
Get medical help today (call your midwife, GP or maternity unit) if you're vomiting and you, as the NHS lists:
- have very dark wee, or haven't had a wee in more than 8 hours
- can't keep food or fluids down for 24 hours
- feel very weak, dizzy or faint when standing up
- have tummy pain or a high temperature
- vomit blood, or are losing weight.
Pregnancy, Birth and Baby says to go to your local A&E if you can't keep fluids down at all. If HG is wearing you down emotionally, tell your midwife or doctor so they can help.
Which supplements should I take?
| Supplement | UK (NHS) | Australia |
|---|---|---|
| Folic acid | 400 micrograms daily, until 12 weeks | At least 400 micrograms daily, first 3 months |
| Iodine | Not part of NHS advice | 150 micrograms daily |
| Vitamin D | Daily in autumn and winter, all year for some | Only if tests show you need it |
- UK. The NHS vitamins page says to take 400 micrograms of folic acid every day from when you start trying (ideally 3 months before) until 12 weeks, or from as soon as you find out you're pregnant. It says taking it for longer won't harm your baby, and advises a daily vitamin D supplement from early October to late March, or all year for some people.
- Australia. Pregnancy, Birth and Baby's folate page says to take a supplement with at least 400 micrograms of folic acid, starting at least one month before trying, and notes most Australian supplements contain 500 micrograms. Australia's healthdirect iodine page says the NHMRC recommends 150 micrograms of iodine a day when planning a pregnancy, pregnant or breastfeeding. If you have a thyroid condition, check with your doctor before taking iodine.
- US. The CDC advises 400 micrograms of folic acid daily, starting at least 1 month before conception and continuing in pregnancy.
Some people need a higher, prescribed dose of folic acid, for example with diabetes, some epilepsy medicines, or a family history of neural tube defects. Ask your GP. The NHS says not to take cod liver oil or supplements containing vitamin A (retinol).
What should I avoid eating and drinking?
Alcohol
The CDC says there is no known safe amount of alcohol in pregnancy and no safe time to drink, and that all types can be harmful. Pregnancy, Birth and Baby's alcohol page says there's no safe time, amount or type, and that the Australian guidelines advise not drinking at all. If you drank before you knew you were pregnant, it says the risk from low-level drinking is likely to be low. Once you know, it's safest to stop.
Caffeine
The NHS foods-to-avoid page, Australia's Pregnancy, Birth and Baby caffeine page and ACOG all set the limit at 200 mg a day. The NHS gives about 100 mg for a cup of instant coffee, 75 mg for a cup of tea, 40 mg for a can of cola and 80 mg for a 250 mL can of energy drink. Pregnancy, Birth and Baby gives 145 mg for a 50 mL espresso. Cup sizes and brews vary, so treat these as rough guides.
Listeria and other food risks
Food Standards Australia New Zealand says listeria can cause miscarriage, premature birth or stillbirth, and that symptoms in pregnancy may seem mild, so get medical attention straight away if you might have it. The CDC says pregnant women are 10 times more likely to get a listeria infection.
| Food | Safer choice |
|---|---|
| Deli and cold cooked meats | Only heated until steaming hot |
| Soft and mould-ripened cheese | Hard cheese, or cooked until steaming hot |
| Pâté and meat spreads | Avoid (Australia) |
| Smoked or raw fish, sushi, oysters, cold prawns | Cooked seafood, eaten hot |
| Pre-cut fruit or salads, rockmelon, raw sprouts | Other whole fruit and vegetables, washed well |
| Soft serve, unpasteurised milk or juice | Pasteurised milk, juice and ice cream |
| Liver | Avoid (too much vitamin A) |
This draws on FSANZ, Pregnancy, Birth and Baby's food guide and the NHS. Advice differs a little by country: the NHS says pasteurised soft cheeses such as feta, mozzarella and ricotta are fine, while Australian advice lists feta and ricotta to avoid unless cooked. For fish, the NHS says to avoid shark, swordfish and marlin, while Pregnancy, Birth and Baby allows up to 100 g a fortnight of those with no other fish. FSANZ also says to reheat food until steaming hot (75°C), and that vulnerable people should eat refrigerated leftovers within 1 day.
When is the first antenatal appointment?
- UK. The NHS antenatal appointments page says you can refer yourself to maternity services as soon as you know you're pregnant. The booking appointment is usually at 8 to 12 weeks, takes about an hour, and includes blood pressure, urine and blood tests, and questions about your health and wellbeing.
- Australia. Pregnancy, Birth and Baby says your first appointment will probably be with your doctor (often your GP), who can confirm the pregnancy. You can then keep seeing your doctor or move to a midwife at the hospital or birth centre you choose, with check-ups usually every 4 to 6 weeks in the first trimester. Australia's healthdirect guide to routine antenatal tests lists first-visit blood tests for your blood group, anaemia and infections, a urine test, and questions about your mood.
Bring a list of any medicines you take, including natural or alternative ones. Pregnancy, Birth and Baby says your doctor or midwife will check they're safe in pregnancy.
Which screening tests are offered in the first trimester?
| Test | UK (NHS) | Australia | US (ACOG) |
|---|---|---|---|
| Dating scan | 11 to 14 weeks | Usually 8 to 14 weeks | Ask your provider |
| Combined screening | 10 to 14 weeks | Blood test 10 to 13 weeks, scan 11 to 13 weeks | 10 to 13 weeks |
| NIPT | Second test after a higher-chance result | From 10 weeks, out-of-pocket | From 10 weeks |
Combined screening pairs a blood test with an ultrasound measurement of the fluid at the back of your baby's neck (nuchal translucency). The NHS screening page says that after a higher-chance result you can choose NIPT, a diagnostic test (CVS or amniocentesis), or no further tests. In Australia, Pregnancy, Birth and Baby's NIPT page says NIPT isn't covered by Medicare, and its Down syndrome screening page gives the combined test's timing. ACOG's screening page gives the US timing.
Screening estimates a chance; it can't tell you for certain. Diagnostic tests can, but they carry a small risk of miscarriage. All three sources stress that screening is your choice. A genetic counsellor can help you think it through.
What are the signs of miscarriage?
Miscarriage is common, and that doesn't make it any easier. Pregnancy, Birth and Baby's miscarriage page says up to 1 in 4 pregnancies end in miscarriage before 14 weeks, and that most happen because of a problem with the baby's development, not because of anything you did or didn't do. March of Dimes says there's no proof that sex or exercise cause miscarriage.
The NHS miscarriage page lists these signs:
- vaginal bleeding, from spotting to heavy bleeding
- cramping or pain low in your tummy
- passing clots or tissue
- fluid suddenly leaking from your vagina.
Bleeding doesn't always mean miscarriage: Pregnancy, Birth and Baby says up to 2 in 5 women have some spotting or bleeding in the first trimester. Sometimes a miscarriage has no symptoms and is found at a scan.
Also know the signs of an ectopic pregnancy, where the pregnancy grows outside the womb. The NHS ectopic pregnancy page says symptoms tend to appear between weeks 4 and 12 and can include pain low down on one side, bleeding or a brown watery discharge, pain in the tip of your shoulder, and discomfort when weeing or pooing.
The weeks after a miscarriage can be hard for you and your partner. Pregnancy, Birth and Baby says support services are there for you, your partner and your family, and your GP, midwife or early pregnancy unit can point you to them. You can also contact Samaritans on 116 123.
Can I exercise in the first trimester?
Yes, for most people. The NHS exercise page recommends 150 minutes of moderate activity a week, plus 2 strengthening sessions. You should be able to talk but not sing. Avoid sports where you could fall or be hit in the tummy, don't scuba dive, and stop if you feel uncomfortable, too hot or unwell.
ACOG suggests starting with as little as 5 minutes a day if you're new to exercise, avoiding overheating, especially in the first trimester, and skipping hot yoga. It says to stop and call your doctor if you have vaginal bleeding, feel dizzy or faint, are short of breath before starting, or have chest pain, a headache, muscle weakness, calf pain or swelling, painful contractions or fluid leaking.
When to get help
These follow the NHS bleeding, miscarriage and ectopic pregnancy pages. Pregnancy, Birth and Baby says to go to your nearest A&E straight away if bleeding is getting worse or you have pain or feel unwell.
Call your maternity unit, early pregnancy unit, midwife or GP now if you:
- have any bleeding or spotting, even if it's light
- have tummy pain or cramping, especially on one side
- have fluid leaking from your vagina
- think you may have listeria, even if you feel only mildly unwell.
The NHS bleeding page says an early pregnancy unit can help if you're less than 20 weeks pregnant. If you can't get through, go to your nearest A&E.
Get medical help today for the signs of hyperemesis gravidarum listed above.
Talk to your midwife or GP at your next visit about nausea you're managing, supplements, medicines or exercise.
Your mood matters too. If you feel very down or anxious, Pregnancy, Birth and Baby says to talk to your doctor or midwife, as it can be a sign of antenatal depression or anxiety. You can also contact Samaritans on 116 123. If you have thoughts of harming yourself, call Samaritans on 116 123 or 999 now. See postnatal mood for more.
What's useful to note down?
The first day of your last period, the supplements you take, and any medicines are worth having for your first appointment. If you're being sick, note how often you vomit, what you've kept down, and when you last had a wee: that's what your midwife or GP will ask. Next, see the second trimester guide.
