First Trimester of Pregnancy

First Trimester of a Pregnancy

Congratulations! You are pregnant!

How did you know it? Did you know you were pregnant in your first week of pregnancy? No?

Most women do not know they are pregnant because your first trimester is calculated from the first day of your Last Menstrual Period (LMP). This means you were still on your periods during your first week of pregnancy. Two weeks later, you start ovulating, and only after 4-6 days, the fertilised egg (embryo) implants on to your uterus lining. This is the time when you actually become pregnant. After implantation, the cells start growing and becomes a foetus.

Let us understand what happens in the first trimester of a pregnancy and what are the different stages and symptoms of first trimester of pregnancy.

 First Trimester of a Pregnancy

  • Morning sickness

    Morning sickness is one of the most common symptoms of first trimester of pregnancy. This medical condition is characterised by Nausea and Vomiting in Pregnancy (NVP). NVP is experienced by around 70-90% of the mums-to-be. According to the National Health Service, hormonal changes during pregnancy is one of the reasons for morning sickness.

  • Sore breasts or tender breasts

    Your breasts become tender due to hormonal changes and start preparing milk ducts for feeding. Until your body adapts the hormonal changes, your breasts remain sensitive.

  • Mood swings

    You will be on an emotional roller coaster throughout the first trimester of a pregnancy. Your moods will swing, and your emotions will change in a matter of seconds. You may feel happy in one moment and fearful or teary-eyed in the next.

  • Fatigue

    In this stage of first trimester of pregnancy, your body is experiencing many physical and emotional and persistently working to keep the foetus safe and healthy. Also, the changes in the levels of progesterone make you feel exhausted.

  • Food cravings/ aversions

    Due to hormonal changes, you may crave for certain foods and develop an aversion to some foods. Also, you may become sensitive towards certain food odours that could trigger NVP at this stage of pregnancy.

  • Constipation

    High progesterone levels slow down the movement of food throughout your digestive system and result in constipation. Also, the iron supplements recommended during this phase may further add to the constipation problem.

  • Urination

    Frequent urination is also one of the common symptoms of first trimester of pregnancy. This is because your uterus grows and puts pressure on the bladder, and you feel like going to peeing all the time. According to, as the blood amount increases in your body during this time, your kidney processes the extra fluid and results in frequent urination.

  • Heartburn/ Acid Reflux

    High levels of progesterone relax the muscles between your stomach and lower oesophagus. These muscles keep the food in the stomach and prevent reflux of the acid. However, when loosened, these muscles let the stomach acids reflux and cause heartburn.

  • Flatulence

    You feel more bloated and flatulence problem because of the slow movement of food in the digestive system.

  • Body Pains

    You may start feeling mild cramps and body pains during the first three months of pregnancy.

  • Implantation bleeding

    You may see pink or red discharge or spot in the initial stages of pregnancy. This spotting or bleeding is called implantation bleeding, indicating the zygote (fertilized ovum) has been implanted.

  • Vaginal discharge

    You may see increased vaginal discharge in the first three months. However, the discharge should be odourless with no burning and itching.

Emergency Symptoms During the First Trimester of a Pregnancy

Get immediate medical help if you are suffering from:
  • Heavy bleeding
  • Acute abdominal pain
  • Dizziness
  • Sudden weight gain
  • Less weight gain than required
These signs during your gestation indicate that something is wrong with your pregnancy. Do not wait for your regular visits, see the doctor immediately.

Stages of Pregnancy in First Trimester

The different stages of pregnancy in first trimester involve all the phases right from your last period to ovulation to the implantation of the embryo, missed periods, confirmed pregnancy and the cell growth into a foetus.

During these stages of pregnancy in first trimester, your little sunshine grows rapidly from a fertilized egg to a foetus. The growth of the embryo is the fastest in trimester than the other two trimesters.

 Baby Growth in First Trimester

According to the American College of Obstetricians and Gynecologists (ACOG), your baby grows from a single-cell into a foetus with heartbeats, muscles, nervous system, cartilage for limbs, genitals and other developments. Here is how your baby grows in the first trimester week after week:
  • Week 1 – There is no baby growth in the first week of pregnancy. Technically, you are not even pregnant at this stage of pregnancy. In this week, you are still on your periods.
  • Week 2 – After 4-6 days of your menstrual period, your body starts getting ready for ovulation. In this stage of pregnancy in first trimester, the sperm fertilizes the mature egg and forms the zygote (fertilized ovum).
  • Week 3 – In this week, the fertilised egg moves through the fallopian tube into the uterus and implants on to the uterine wall. The single-cell zygote develops into a ball of cells called a blastocyst. Here on, the baby’s development begins.
  • Week 4 – In this week, your baby enters the embryonic stage and is called an embryo. It is a little as the size of a sesame seed.
  • Week 5 – Your baby is rapidly growing, and major organ systems begin to form at this stage. Specifically, brain and heart start shaping. Your baby is the size of a grain. The heart starts beating and pumping the blood. Webbed fingers, eyes and limbs, gastrointestinal tract, kidneys, liver and reptilian face forms in this week. Also, the placenta is formed in this week to provide nourishment to the baby.
  • Week 6 – You can see your baby through ultrasound. It may be quarter the size of an inch. By the sixth week of pregnancy, your foetus grows the brain and spine. It starts developing the neurons. A heart with four chambers is formed. Eyes and ears start shaping, and fingers are formed. Stomach and kidneys start functioning, and the salivary glands start shaping in the mouth. The baby forms jaws with gums and teeth buds.
  • Week 7 – The embryo starts taking the shape of a human form and develops face with distinct features. It grows eyes (with closed eyelids), ears, nostrils and mouth (tongue and tooth buds are distinctly visible). The nervous system, digestive system, brain, kidney, liver, pancreas, intestines and umbilical cord are noticeable.
  • Week 8 – Your baby is now the size of a cranberry bean. In this week, the genital buds of the foetus begin to form. The embryo continues to develop the brain, and the limbs grow longer. The spine develops a vertebral column, and the head can be differentiated from the body. Lungs begin to form, and the umbilical cord pumps blood to the foetus.
  • Week 9 – Eyes, ears and mouth are distinctly visible. Limbs grow and wrists, ankles, toes and fingers develop. All the joints, such as ankles, elbows, shoulders and knees form and start working, and the skeleton hardens. Neck region is defined. Digestive system, nervous system, heart and blood flow start functioning rapidly. Genitalia develops internally.
  • Week 10 – In this foetal stage, your baby is the size of a strawberry and developing muscles. The facial features are more distinct, and the foetus starts swallowing amniotic fluid. Hair begins to grow, and nails start developing. Cartilage is replaced with bones, and the foetus can bend knees and elbows. Fingerprints develop on the skin. Genitalia forms externally, and all the major organ systems continue to function.
  • Week 11 – About the size of a sprout, your foetus develops human facial features with nose and lips. It can open and close the fists, and the muscles start working with the nerves. Genitalia is distinguishable and can be detected through an ultrasound. All the vital systems continue to develop and function. The foetus begins to absorb water and glucose from the amniotic fluid. The baby moves inside, but it cannot be felt by the mother.
  • Week 12 – During this stage of pregnancy in first trimester, your baby is the size of a lime and starts developing larynx and voice box in the trachea. All the major organ systems continue to grow and function. The baby gets its nourishment through the placenta and umbilical cord.
  • Week 13 – Your pea-pod sized baby starts producing insulin, secreting bile and forming full lips and mouth. The limbs continue to grow, and all the organ systems function.

Dos and Don’ts During the First Trimester of a Pregnancy

Do the following in the first three months of pregnancy to avoid any complications
  • Eat small meals throughout the day. This helps you in managing your morning sickness effectively and be energetic throughout the day.
  • Get enough rest and get a full night sleep.
  • Eat a healthy and balanced diet. Include fruits, vegetables, dairy products, milk and whole grains in your diet. You can give in to your cravings except if you feel like eating non-edible things, such as clay.
  • Drink enough water and fluids to avoid dehydration.
  • Express your emotional feelings and mood swings without any worries. It is normal to feel mood swings in this stage of pregnancy.
  • Workout every day for at least 30 minutes.
Avoid doing the following:
  • Drinking alcohol
  • Smoking tobacco or other substances
  • Eating greasy, spicy, oily or uncooked/undercooked food
  • Suppressing your emotions
  • Drinking too much of caffeine
  • Taking unprescribed or over the counter medication
  • Standing or sitting for too long

Remember to enjoy this journey of 9 months. Do not let the hearsays or your fear take away the beauty of this temporary phase.