Pregnancy by Trimester

Feb 16, 2022 | 2 minutes Read

Congratulations, you're pregnant! If this is your first time, you're in for one amazing ride.

One of the best things to do is to educate yourself on the wild and wondrous stages that you and your growing baby will go through.

Your pregnancy will span anywhere between 37 and 42 weeks, or approximately nine calendar months. If your baby is born prematurely, that means it will be born before 37 weeks.

All pregnancies are measured from the first day of a woman's last normal menstrual period (LNMP). If you are unsure when your LNMP was, ask your chosen healthcare professional about having an early ultrasound. An ultrasound can be an accurate way of finding out the gestational age of your baby.

The weeks of your pregnancy are commonly grouped into three trimesters. Each trimester represents three months and a different and distinct stage of your pregnancy.

Discover what you and your baby will experience in each trimester.

First Trimester

The beginning of this trimester is measured from before your baby was a twinkle in your eye. It is measured from the first day of your LNMP, which is before you even conceived. This is because it's the first day that your body starts preparing for a pregnancy.

The first trimester of pregnancy spans from week 1 to 13, or the first three calendar months. And for about half of this time, you might not even know you're pregnant.

You may find out you're pregnant by doing a home pregnancy test. By the end of this trimester, you should also have your pregnancy confirmed by a healthcare professional. Choose someone who you feel comfortable with and who you can afford. If you haven’t visited a pregnancy care provider yet now is the time. This may be a midwife, obstetrician, or family medicine physician.

Second Trimester

Making it past the first trimester is a reassuring feeling for all pregnant women. About 95% of your baby's core development is behind both of you. Your baby's essential organs and body systems should be in place and fully formed.

In the second trimester your baby will continue to mature and increase in size. Amazingly, this increase will be by 300 to 400% in your second trimester. He or she will also start to look more and more like the little person they will become.

Exhaustion and nausea experienced in early pregnancy should also begin to settle down. This trimester is commonly labeled as the “feel-good trimester.” Hopefully, you will have more energy, be feeling more comfortable and just feel better overall. Try to make the most of these exciting three months.

Third Trimester

Reaching your third trimester will give you a great sense of achievement.

All your baby's organs and systems will be preparing for life outside the womb. Although they have been fully formed since around 12 weeks of pregnancy, an enormous amount of maturity and development has been taking place since then. You have probably been feeling some of the growth and development.

Your baby's movements will also become stronger and more defined in the third trimester. As your baby grows, it will quickly run out of space to wriggle around in your uterus. This means that you will feel every kick and movement more clearly when they shift position.

Your third trimester may last up to 42 weeks. And your baby could be born anytime onwards from 37 weeks and be considered full-term. Only 5% of babies are born on their exact due date—in fact, the average birthday is just past 40 weeks. Remember that every pregnancy and every baby is unique so do your best to go with the flow and to make the most of this amazing time.

The information of this article has been reviewed by nursing experts of the Association of Women’s Health, Obstetric, & Neonatal Nurses (AWHONN). The content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment. For more advice from AWHONN nurses, visit Healthy Mom&Baby at