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What is really going on during pregnancy

Quick notes:

  • Pregnancy is broken down into three trimesters

  • Each trimester represents important steps of pregnancy and development

Most women freak out a little when they find out they are pregnant, especially if it is their first. Knowing what to expect can go a long way in calming your nerves.

Pregnancy stages

Pregnancy is broken down into three time periods: the first trimester, the second trimester, and the third trimester.

1. First trimester- Weeks 1-12


For moms, the first trimester is usually when you realize that something is different with your body and, more often than not, when you discover you are pregnant. Some signs include:

  • Chronic fatigue
  • Moodiness
  • Intense cravings
  • Headaches
  • Heartburn and constipation
  • Needing to urinate every five minutes (or so it seems)
  • Morning sickness


-4-6 weeks

At this point, the baby does not look like a baby yet. However, its heart, brain, and spine have started forming.

-8 weeks

The arms, legs, fingers, and toes are becoming more visible, all major organs are beginning to form, and its eyelids have formed. Its heart is regularly beating, and it is about an inch long.

-12 weeks

The sex organs are developed enough to determine sex. Additionally, the nerves and muscles are beginning to work in tandem, so it will start to make fists. The eyelids close at this time to protect the eyes, and the baby has grown to almost three inches long.

Unsplash / Kelly Sikkema

2. Second trimester- 13 to week 28.


The good thing for mom is that most of the discomfort and morning sickness has diminished. The second trimester can be one of the least uncomfortable stages for many moms. However, your baby is growing, and your body must accommodate, so you may still experience the following:

  • Aches and pains in the back and belly
  • Stretch marks on the stomach, breasts or thighs
  • Swelling ankles, face, or feet
  • Itchy skin
  • Tingling in the hands


-16 weeks

Your baby is beginning to look much more like a baby. The skin, muscle tissue, and bones are forming. The baby has grown to about four or five inches, and it begins to make sucking motions.

-20 weeks

Most moms start to feel movement at this point. The baby can hear now and will begin to recognize your voice. Its eyebrows, eyelashes, fingernails, and toenails have formed, and it has grown to about six inches.

-24 weeks

The baby’s lungs are developed. There are now official fingerprints and footprints, your baby is getting into a sleeping routine, and hair is growing on its head. At this point, your baby is about 12 inches long.

3. Third trimester- Week 29-40


It is about to get uncomfortable again. You may not be able to find a comfortable position to sit or sleep. It might also be difficult to breathe, but soon you will have the little miracle in your arms.


-32 weeks

You might start thinking you are carrying a soccer player or gymnast. The bones are forming, and your baby is putting them to use. The lungs are practicing their function, eyes are reopening, and the body is storing iron and calcium. Your baby is 15-17 inches now.

Around week 32 of pregnancy is when moms start thinking they might be carrying a world-class soccer player or gymnast 

-36 weeks

The baby is storing more fat and getting bigger, meaning it will not be moving so much. At this point, the baby may be as long as 19 inches.

-37-40 weeks

By 39 weeks, organs can function on their own. Most babies turn upside down to prepare for birth. The average birth sizes are 19-21 inches and 6.2-9 pounds.

A deeper dive – Related reading from the 101:

Great ways to help produce more breastmilk if you choose to breastfeed

Tips for planning your nursery if you just can’t wait to find out what you are having