First Trimester of Pregnancy: What to Expect in Weeks 1–12

September 4, 2023

The first trimester can feel like a strange mixture of excitement, uncertainty and change.

You may have known you were pregnant almost immediately, or discovered several weeks into your pregnancy. You may be experiencing lots of symptoms — or hardly any at all.

Every pregnancy is different.

The first trimester covers approximately the first 12 weeks of pregnancy, during which your baby's early development happens remarkably quickly and your body begins adapting to pregnancy.

Here are some of the things you may experience and the practical steps worth taking during these early weeks.

What Happens During the First Trimester?

Pregnancy is dated from the first day of your last menstrual period, which means the first couple of weeks of the pregnancy calculation occur before conception has actually taken place.

During the weeks that follow, your baby's major organs and body systems begin developing.

Meanwhile, changing hormone levels can produce some very noticeable symptoms — even though you may not look pregnant yet.

What Are Common First-Trimester Symptoms?

Not everyone experiences the same symptoms, and having fewer symptoms doesn't necessarily mean anything is wrong.

Common early-pregnancy symptoms can include:

nausea or vomiting
tiredness
sore or tender breasts
needing to urinate more frequently
changes in taste or smell
constipation
increased vaginal discharge
food likes and dislikes
mood changes

The NHS notes that pregnancy symptoms often begin at around 4 to 6 weeks, although experiences vary considerably.

Morning Sickness Isn't Just in the Morning

Despite its name, pregnancy sickness can happen at any time of the day or night.

It commonly begins early in pregnancy and usually settles between weeks 16 and 20, although it can continue for longer.

If nausea is making eating difficult, small frequent meals, rest and sipping fluids regularly may help.

We've covered this in more detail in our guide to Best Ways to Cope With Morning Sickness.

When Is Pregnancy Sickness More Serious?

Severe pregnancy sickness can sometimes develop into hyperemesis gravidarum, which may require treatment.

Contact your midwife, GP or NHS 111 if you're vomiting and, for example, cannot keep food or fluids down for 24 hours, haven't urinated for more than eight hours, have very dark urine, feel weak or faint, have abdominal pain, a high temperature, vomit blood or are losing weight.

Feeling Exhausted in Early Pregnancy

Extreme tiredness can be another feature of the first trimester.

You don't need to “push through” it.

Rest when you can and consider where other people can take some of the load. That might mean a partner preparing dinner, rearranging social plans or simply accepting that your usual pace isn't realistic every day.

Pregnancy doesn't have to look productive.

What Should You Eat During the First Trimester?

You don't need a special first-trimester diet.

A healthy, varied diet will generally provide most of the vitamins and minerals you need, although there are some important pregnancy supplements and food-safety recommendations to be aware of.

We've covered pregnancy nutrition separately in Nourishing Your Pregnancy: Vitamins, Minerals and Meals.

Folic Acid in the First Trimester

Folic acid is particularly important during early pregnancy.

The NHS recommends 400 micrograms of folic acid every day, ideally starting before conception and continuing until the end of the first 12 weeks of pregnancy.

Some people are advised to take a higher 5mg dose, which is prescribed by a GP. This can apply in certain circumstances, including some medical conditions, medicines or a personal/family history of neural tube defects.

Don't simply increase the dose yourself — speak to your GP or midwife if you're unsure what you need.

What About Vitamin D?

The NHS currently recommends 10 micrograms of vitamin D each day between early October and late March during pregnancy because we cannot make enough from sunlight during these months.

Some people are advised to take it throughout the year, depending on factors including sun exposure and skin tone.

Avoid supplements containing vitamin A in the form of retinol and avoid cod liver oil during pregnancy.

When Should You Contact a Midwife?

You don't need to wait until the end of the first trimester.

In England, you can usually refer yourself directly to NHS maternity services as soon as you know you're pregnant. The first midwife or “booking” appointment normally takes place between 8 and 12 weeks, and NHS guidance says it should happen by 10 weeks where possible.

If you have a long-term health condition or take regular medication, you should also contact your GP or specialist to discuss your care. Don't stop prescribed medication without medical advice.

What Happens at Your First Midwife Appointment?

Your booking appointment is an opportunity to discuss your health, pregnancy and individual circumstances.

Your midwife will ask about areas including your health, previous pregnancies and any medical conditions, so that your antenatal care can be planned appropriately.

It's also your opportunity to ask questions.

Write them down beforehand if that helps — particularly because it's remarkably easy to forget everything you intended to ask once you're sitting in the room.

What About Your Emotional Health?

Finding out you're pregnant doesn't produce one compulsory emotion.

You might feel excited, anxious, happy, overwhelmed, uncertain — or several of those things at once.

You may also find that your feelings change from one day to another.

Try not to compare your response with an idealised version of how pregnancy is “supposed” to feel.

If worry, anxiety or low mood is affecting your everyday life, speak to your midwife or GP. Mental wellbeing is part of pregnancy care too.

Our guide to Pregnancy Guilt and Worry: Looking After Yourself as a Mum-to-Be explores this in more detail.

Looking After Yourself During the First Trimester

Self-care doesn't need to mean buying anything.

During these early weeks, it might simply mean:

getting more sleep
eating whatever nutritious foods you can comfortably manage
keeping water nearby
asking somebody else to cook
taking a gentle walk if you feel up to it
declining plans when you're exhausted
talking about how you're feeling
accepting help

If you're uncertain whether a medicine, supplement, herbal product or complementary therapy is appropriate during pregnancy, check with a pharmacist, midwife, GP or other appropriate healthcare professional rather than relying on a “pregnancy safe” marketing claim.

You Don't Have to Prepare for Everything Yet

It can sometimes feel as though a positive pregnancy test immediately produces an enormous to-do list.

Nursery. Pushchair. Birth plan. Baby names. Childcare. Hospital bag.

You don't have to solve all of that during the first trimester.

Starting your antenatal care and looking after yourself are much more immediate priorities.

There will be time to prepare for what comes next.

What Comes After the First Trimester?

At around 13 weeks, you move into the second trimester.

For some people, symptoms such as nausea and extreme tiredness begin to ease around this stage, although pregnancy experiences vary.

Our next guide explores what to expect during the Second Trimester of Pregnancy.

And eventually there is another transition that's surprisingly easy to overlook: the period after pregnancy.

The first weeks following birth are often described as the fourth trimester, when both mother and baby are adapting to life after pregnancy.

Read our Fourth Trimester Guide