What Happens During the First Trimester?

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Published On
17 Jul, 2023
Read Time
6 minutes

It's often during the first trimester that pregnant people encounter some of the most challenging pregnancy symptoms. This means that although it's an exciting time that's crucial for the development of the fetus, it can also be tough.

We've written this guide to help you learn about the most common first-trimester symptoms. We'll also cover some top tips, and answer some of the most-asked questions that parents-to-be have about early pregnancy.

How long is the first trimester?

The first day of your last period marks the first day of the first trimester. It ends on the last day of the 12th week of your pregnancy.

Three trimesters make up a pregnancy. After the first trimester, you move into the second trimester, then the third trimester.

What to expect in the first trimester

During the first trimester of pregnancy, a lot of changes take place in a person's body.

The fertilized egg implants itself in the uterus, and the placenta starts to develop. Hormones like progesterone and estrogen begin to increase, causing symptoms like fatigue, nausea, and breast tenderness (we'll cover those next). The baby's major organs and body systems also start to form.

First-trimester symptoms

Throughout the first trimester, lots of changes happen. While each pregnancy is unique, lots of people experience the same set of pregnancy symptoms. These are caused by both hormonal and physical changes, and include:

  • Missing a period: If your menstrual cycle is regular, missing a period is often the earliest sign of pregnancy.
  • Spotting or implantation bleeding: Experiencing some light bleeding that resembles a light period in the initial stages of pregnancy is known as implantation bleeding. It should only involve spotting or a small amount of blood loss.
  • Changes to discharge: During pregnancy, increased blood flow to the pelvic area stimulates the body's mucous membranes. This can lead to an increase in cervical mucus and a thin, milky, white vaginal discharge that's sometimes known as leukorrhea.
  • Morning sickness or nausea: Morning sickness is a common pregnancy symptom that's characterized by nausea and vomiting. It typically happens during the first trimester and can occur day or night.
  • Tiredness and fatigue: It's quite common for pregnant people to experience a heightened sense of fatigue. This is because of hormonal shifts, increased blood production, and the development of vital organs which can leave you feeling drained. It's important to prioritize rest and self-care.
  • Food cravings or aversions: You may notice that you crave certain foods or feel put off by foods and drinks that you used to like.
  • Larger, tender breasts: Increasing levels of progesterone during the first trimester can make your breasts bigger and tender, achy, and sensitive. Remember to wear a comfortable, well-fitting bra to support them.
  • Needing to pee more than usual: You may feel like you need to pee more often than usual, especially at nighttime.
  • Constipation and bloating: During the early stages of your pregnancy, you may experience constipation and bloating. Drinking plenty of water and eating foods that are high in fiber can help.

First-trimester pregnancy belly: week by week

Although you'll experience lots of physical symptoms and changes in the first trimester, you might not notice a baby bump developing until around week 10.

While some people may see a visible pregnancy bump by the end of their first trimester, others may not. It just depends on your body and your baby's development. It's worth keeping in mind that everyone's pregnancy experience is different.

How your baby develops in early pregnancy

During the first trimester fetal development starts with the egg being fertilized and ends when the fetus has all its organs, and its body systems are developing. By the end of the first trimester, the fetus is about the size of a peach!

Signs your pregnancy is going well in the first trimester

The truth is, some of the symptoms you experience during the first trimester can be unpleasant, but all the common symptoms of early pregnancy that we've mentioned above are normal and act as signals that your first trimester is going to plan.

On the other hand, you may feel great and not experience these common first-trimester symptoms. If that's you, don't worry. If your medical appointments confirm that everything is ok with your pregnancy, then there's no need to worry.

Danger signs of pregnancy in the first trimester

Some symptoms can sometimes be warning signs during pregnancy, and you should seek medical advice if you experience any of the following:

  • Severe abdominal pain: Stomach pain during pregnancy is normally caused by trapped wind, constipation, or ligament pain, and is commonly nothing to worry about. But in some cases, it can be a warning sign of something more serious - such as miscarriage, ectopic pregnancy, a UTI, and placental abruption, If you're pregnant and concerned about stomach pains, it's best to speak to your doctor or midwife for reassurance.
  • Heavy vaginal bleeding: Spotting or light implantation bleeding is common during the first trimester, but you should always speak to your doctor if you experience heavy bleeding from your vagina during pregnancy.
  • Severe dizziness: Dizziness that's caused by heat, hunger, nausea, or getting up too fast is usually just part of being pregnant. But if you're pregnant and often feel dizzy or become so dizzy that you faint, you should see your doctor. Dizziness or feeling faint can sometimes be caused by low iron levels or anemia. This is a common side effect of pregnancy and can be treated by taking iron supplements prescribed by your GP or midwife.
  • Fever: A fever or high temperature above 99.5°F during pregnancy could harm you and your baby and needs immediate medical attention.
  • Itching that's worse at night: Some slight itching during pregnancy around your tummy is normal, but itching can also be a sign of a condition called intrahepatic cholestasis of pregnancy or ICP. You should speak to your doctor or midwife if you have itchy palms and soles of your feet that are worse at night.
  • Rash: You should seek medical attention as soon as possible if you're pregnant and spot any kind of rash, especially if you've been around someone with shingles or chickenpox.
  • Mental health struggles: Don't hesitate to seek support if you're pregnant and feeling depressed, anxious, or like you can't complete your usual, everyday tasks - especially if these feelings last for two weeks or longer.

First trimester tips

  1. Add all your appointments and tests to your diary: Your antenatal appointments with your healthcare team are important. They allow them to check on the health of you and your baby, give you useful information, and answer any questions you may have along the way.
  2. Take vitamins: Once you find out that you're pregnant, you should take prenatal vitamins that make up for any nutritional deficiencies during pregnancy. These include folic acid, calcium, and iron supplements.
  3. Get advice on safe prescriptions and medications: You should check with your pharmacist or doctor that any medication you're planning to take is safe to use during pregnancy before you take it. This includes anything prescribed by a doctor or purchased from a pharmacy or store, including painkillers.
  4. Eat well and stay hydrated: While it's ok to give in to your candy craving during pregnancy, it's important to stay hydrated and eat a balanced diet to support your baby's growth and to keep yourself feeling healthy.
  5. Keep active: Staying active during pregnancy is an excellent way to maintain your energy levels, boost your mood, and prepare for labor. It's safe for your baby, and if you feel comfortable, you can do light exercise throughout your pregnancy, unless you've been told not to exercise by a medical professional.
  6. Don't be afraid to raise any concerns: Always speak to your healthcare provider if you have any concerns or questions about your health, your pregnancy, or your baby's development..

What should I avoid during the first trimester of pregnancy?

It's important to be cautious during the first trimester of pregnancy and avoid certain things that could potentially harm the developing fetus, such as:

  • Alcohol
  • Caffeine: Limit your intake to 200 milligrams per day
  • Certain fish that contain high levels of mercury
  • Certain medications: Ask your healthcare provider if any medication you'd like to take is safe to consume during pregnancy
  • Illicit drugs
  • Raw or undercooked foods
  • Smoking
  • Cat litter: This can carry a parasite that causes toxoplasmosis which can be dangerous for your unborn child, so it's best to avoid handling it when you're pregnant.

Individual circumstances may require unique precautions, so it's always best to consult with your healthcare provider for personalized advice based on your specific situation.

The first trimester finishes at the end of the 12th week of pregnancy. After that point, you're in the second trimester.

We asked our Instagram followers what the first trimester felt like for them, and here's what they told us:

  • "I had zero symptoms apart from lack of period."
  • "Struggling with food aversions and sickness, while trying to act normal."
  • "The longest! Because you're keeping it quiet, but you want to explode and tell the world."
  • "Like I've got a little secret."
  • "Emotional and overwhelming."
  • "Mine was good, felt very hungry all the time."
  • "A real out of body experience, didn't feel like myself one bit."
  • "Tired and constantly feel sick but not being sick. Smells were triggering."
  • "Nausea, constantly hungry, always sleepy."