October 2022

In the first trimester of pregnancy, what can you expect?

We often hear of pregnancy being broken down into stages, but what do these stages mean? How does your body react to each stage or trimester? These are great questions and there are many different books and articles that can prepare you for each trimester. The first trimester is the first stage of pregnancy that you will go through and it is important to be prepared for what this stage means for you and your future child.


What is the first trimester?

The first trimester starts on the first day of your last period. This trimester starts before you are pregnant and it ends at the thirteenth week of pregnancy. This trimester consists of some pretty quick changes for you and your baby. Many women say this is the most difficult trimester to get through. Many women experience morning sickness and hormonal mood changes during this trimester. You may feel very tired as well since your body is adjusting to new hormones and pregnancy. This period of time is difficult, pregnancy is a huge change. Drinking and certain medications will need to be cut out and you may have trouble adjusting to changes in your social life without drinking. It is important to be gentle with yourself during this period, even if it feels impossible you will get through it. [1]


 first trimester of pregnancy


What changes in your body happen during the first trimester?

There are a few changes in your body that you can expect during the first trimester of pregnancy including:

  • After conception, your breasts will feel swollen and tender. This should go away in a few weeks.
  • Nausea is also very common, typically called morning sickness. This can happen at any point in the day or at night. It helps to eat small amounts of food slowly. 
  • Frequent urination is a common symptom, this happens because your kidneys are processing extra fluid.
  • Food cravings or aversions to certain foods are common. Your sensitivity to smell and taste will change. You may start to be disgusted by the food you usually like or enjoy odd combinations of food.
  • Heartburn is common due to the valve between your stomach and esophagus relaxing from hormones. 
  • Constipation is also a common symptom due to high levels of progesterone slowing the movement of food.


These changes to your body can seem overwhelming or frustrating at times. It is important to communicate with your doctor as he or she can advise you on how to alleviate some of these pregnancy symptoms. [2]


The baby’s growth during the first trimester.

The first trimester is very important for the growth of a healthy baby. Despite the fetus being so small during this period, this stage is crucial for development. During this period when the embryo is implanted in the uterine wall many developments happen including:

  • The amniotic sac surrounds the fetus. This keeps the fetus safe from injury and ensures the temperature is regulated.
  • The placenta also grows and this organ is attached to the uterine wall. 
  • The umbilical cord forms connecting the fetus and the placenta. The umbilical cord transfers oxygen and nutrients to the fetus.


The first trimester is when the most growth and changes occur. In the first eight weeks of pregnancy, the fetus is called an embryo. At the end of the first trimester, the embryo becomes a fetus that is about nine centimeters long. During this period all of the fetus’ organs form, eyes and ears are forming, the fetus’ heart is beating, and the embryo is beginning to take a human shape. By twelve weeks the fetus has fingernails, eyelids, arms, legs, and the fetus’ voice box begins to form. This is an amazing period of growth for the fetus and it is important to closely monitor the fetus during this time. Your doctor may recommend lifestyle changes at this point and this time can seem very scary. It is important to listen to your doctor and remember that your body can provide everything the fetus needs which is amazing in itself. [3]



1 https://www.webmd.com/baby/guide/first-trimester-of-pregnancy

2 https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/pregnancy/art-20047208

3 https://www.stanfordchildrens.org/en/topic/default?id=first-trimester-85-P01218