First trimester: Physical changes and common discomforts

First trimester: Physical changes and common discomforts
Here are the main physical changes you’ll notice and the most common discomforts that can develop during the first trimester.

You’ve just found out you’re pregnant. Your belly hasn’t started to grow yet, but already you can feel your body transforming. Fatigue, nausea, firmer and more sensitive breasts. Discover the main physical changes that occur during the first trimester and some common discomforts you may experience.

Physical changes

  • You stop menstruating.
  • Your uterus starts expanding, but you’ll only notice a baby bump around the fourth or fifth month of pregnancy. If this is not your first pregnancy, however, you may develop a belly during your third month. Two months in, your uterus starts to grow 4 cm per month. At 12 weeks, it’s roughly the size of a grapefruit.
  • Your breasts start to swell. They become heavier, firmer, and more sensitive. They may even be slightly painful. Your nipples and areolas also begin to grow larger and firmer.
  • To meet your baby’s needs, your body must increase blood flow to the uterus. Your heart rate therefore rises six weeks into your pregnancy and remains high until delivery.
  • The release of hormoneslowers your blood pressure and slows down your digestive system. You may also produce more saliva, sometimes excessively.
  • You feel out of breath. This is normal, as oxygen demand increases 15 to 20 percent during pregnancy. Your respiratory rate hasn’t increased. Rather, each breath pulls more oxygen into your lungs.
  • You start to put on a bit of weight. However, some women may lose weight during this period due to nausea and vomiting.

Common discomforts

Pregnancy affects a woman’s entire body. The cardiovascular, digestive, respiratory, nervous, reproductive, and urinary systems are all impacted. It’s therefore normal to feel various aches and pains over the next few months.

Below is a list of the most common discomforts experienced in the first trimester. To learn more about a specific ailment, click on its name and consult the fact sheet.

If you’re concerned about any of your symptoms, write them down and discuss them with your health care provider during your next appointment. Don’t hesitate to contact them between appointments or call Info-Santé (811) if your symptoms are worrisome. Some over-the-counter medications can relieve certain discomforts, but it’s important to talk to a doctor or pharmacist before taking any.

Things to keep in mind

  • Certain physical changes develop in the early months of pregnancy.
  • These changes affect the woman’s entire body.
  • If you’re concerned about any of your symptoms, discuss them with the health care professional monitoring your pregnancy.


Naître et grandir

Scientific review: Roxanne Piché, nursing adviser, Maternal Fetal Medicine Clinic, CHU Sainte-Justine
Research and copywriting: The Naître et grandir team
Updated: August 2019



Note: Hyperlinks to other websites are not updated regularly, and some may have changed since publication. If a link is no longer valid, use search engines to find the information you’re looking for.

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