In the last blog post, I covered the physical changes a baby goes through during the first trimester of pregnancy. This post is going to cover physical changes that occur during the second trimester. We left off at week 12 where the baby is fully formed and is moving around quite a bit (even though you can’t feel it). In the second trimester, the baby continues to grow, facial features become more apparent, and you start to feel the baby’s movements. 

Week 13

     In the last post, I mentioned the amniotic sac, which is a fluid-filled sac the baby is in throughout the pregnancy. The fluid that fills the sac is called amniotic fluid. At this point in the pregnancy, the baby will swallow some of the fluid and will excrete it in the form of urine. In short, your baby can now pee! (3)

     The amniotic fluid they swallow will also make up the baby’s first bowel movement (poop). The very first poop usually happens around 24 hours after birth and is black and sticky. (3)

Week 13 Fun Facts

  • Baby is the size of a pea pod. (2)
  • Baby has fingerprints. (2)
  • If the baby is a girl, her ovaries already hold over 2 million eggs. (2) 
  • Baby’s bones and teeth are becoming stronger. (1)

Week 14

     This week, the part of the baby’s brain that allows facial movement has matured, so they can now move their facial muscles. They can even suck their thumb at this point. (2) This is also when the gender of the baby is obvious and hair follicles have started to form. (1) 

Week 14 Fun Facts

  • Baby is the size of a lemon (2)
  • Baby is kicking and punching quite a bit, but you are still unable to feel it due to the small size. (4)

Week 15

     The baby’s eyelids are still fused shut, but they can now sense light. Their legs become longer than their arms this week and they are becoming more active and mobile. They are starting to look more like a person this week, especially with their different facial expressions and ability to yawn. (5)

Week 15 Fun Facts

  • Baby is the size of an apple (2)
  • If you shine a flashlight on your belly, the baby might move away from the light. (2)
  • An ultrasound may be able to detect the gender of the baby at this point. (2)

Week 16 

     This week, the baby’s head is more upright and its ears are almost in their permanent position. (2) The baby’s heart is now pumping 25 quarts of blood every day and its skin is thickening. (6) 

Week 16 Fun Facts

  • Baby is the size of an avocado (2)
  • Movement can be detected on an ultrasound, but you still cannot feel it. (2)

Week 17

     This week the baby’s bones are now hard instead of soft cartilage. (1) The umbilical cord continues to grow in length and thickness and sweat glands are starting to develop. (7)

Week 17 Fun Facts

  • Baby is the size of a turnip. (2)
  • Baby’s heart is now pumping 100 pints of blood each day. (1)
  • Baby has toenails. (1)

Week 18

     This is the week your baby can start to hear noises. (1) You will also be able to see their facial features like eyes, ears, nose, and lips on an ultrasound. (8) This is also the week when the baby will develop hair, including eyelashes and eyebrows. (8) 

Week 18 Fun Facts

  • Baby is the size of a bell pepper. (2)
  • You might be able to feel your baby moving this week. (2) 

Week 19 

     At this point in the pregnancy, the baby’s physical growth slows down. (1) But their brain is rapidly growing which is causing their senses (taste, smell, hearing, vision, touch) to heighten. This is also when a cheese-like coating called vernix caseosa forms on the baby’s skin. Sometimes the amniotic fluid can irritate the baby’s skin, so the vernix caseosa helps protect it. 

Week 19 Fun Facts

  • Baby is the size of a tomato. (2)
  • Baby’s fingerprints and toeprints are now permanent and unlike anyone else’s. (2)

Week 20

     You can most likely feel the baby moving at this point. You may even feel them become startled by a noise while sleeping. (1) The baby can also swallow at this point and their digestive system is starting to make the meconium (first poop). (2)

Week 20 Fun Facts

  • Baby is the size of a banana. (2)
  • This is halfway through the pregnancy! 
  • If you feel the baby moving it will feel like “flutters.” 


Week 21

    At 21 weeks, the baby is covered with peach-like fuzz called lanugo that helps keep their thin and translucent skin protected. Their movements move from “flutters” to “jabs”, which you will probably feel more of. (11)

Week 21 Fun Facts

  • Baby is the size of a carrot (in length). (2)
  • You might see the baby sucking their thumb on an ultrasound. (11)

Week 22

    Hair on the baby’s head is now visible as well as eyebrows. (2) If the baby is a boy, his testes will drop this week. (1) This is also when fat will start forming under the skin. (1)   

Week 22 Fun Facts

  • Baby is the size of a spaghetti squash (2)
  • Baby can most likely hear your heart beating, your digestive system operating, and your lungs moving when you breathe. (12)


Week 23

    This week the baby’s hearing continues to improve. They can most likely hear and recognize your voice when you speak and they will prefer it over other voices. (13) This is also when the baby’s digestive system starts working. There is nothing to digest yet, but the motions needed to move food are operating. (12)

Week 23 Fun Facts

  • Baby is the size of a large mango. (2) 
  • Imprints on the baby’s hands and feet start to form. (1)

Week 24

    The baby’s respiratory system is continuing to grow. This week little sacs are multiplying in the lungs that will help the lungs take in oxygen after birth. (14) The baby still does not have a lot of body fat, but that is going to change soon! (14)

Week 24 Fun Facts

  • Baby is the size of an ear of corn. (2)
  • Baby can raise their eyebrows up and down. (14)


Week 25

    This week the baby starts gaining more fat which makes the skin less wrinkly and more smooth. (25). They also are spending most of their time sleeping in REM (rapid eye movement). This means that even though the baby’s eyes are closed, their eyes are moving rapidly from side to side. (1)

Week 25 Fun Facts

  • Baby is the size of a rutabaga. (2)
  • If you could see the baby, you would be able to tell what color and texture the hair is. (15)

Week 26

     This is a big week for the baby’s lung development. They have started inhaling and exhaling amniotic fluid, which is preparing their lungs to breathe in oxygen. (16) 

Week 26 Fun Facts

  • Baby is the size of a bunch of scallions. (2)
  • The baby is more aware of sounds and may be frightened by loud noises. (16)

Week 27

    This is the last week of your second trimester! The baby’s lungs are now making surfactant, which is a liquid that will help them breathe after they are born. (17) They also now have a regular sleep/wake schedule and their brains are very active. (2)

Week 27 Fun Facts

  • Baby is the size of a head of cauliflower. (2)
  • Baby can now open and close their eyes. (2)

     The second trimester is done! Your baby grew from about 3 ⅓ inches to 9 inches long and from 1 ½ ounces to around 2 lbs. (1) In the next post, we will cover the 3rd trimester where the baby’s brain continues to develop, they can turn their head from side to side, and they will gain a lot of weight in just a few weeks.

If you have any questions or concerns, please contact;

Nurturing Center of Lubbock
3303 66th Street
Lubbock, TX 79413
Phone: 806-780-6853 (available 24 hours)
Text: 806-317-4480



Marlee Henn, RN

Marlee has been a nurse for two years and currently works in a functional medical clinic and part time in a long term acute care center. She has a passion for natural living, women’s health, and education.