20 and 21 weeks development

You have been up to a lot of growing my little princess so here we go…

The rapid growth stage is about over. While things have slowed down, this next stage is vital to survival. Counting down to 24 weeks my love!

20 Weeks Development:

  • In the eye, your retina now has discrete layers.
  • In the teeth, your enamel begins to develop between 18 and 22 weeks.
  • Beginning at 20 weeks, ultrasound scans show a distinct type of motion in your fetal voice box, or larynx, similar to movements made during speaking. How cool is that?! And we know you were chatting up a storm at your last ultrasound 🙂
  • From 20 to 22 weeks, fetal movement, breathing activity, and your heart rate begin to follow daily cycles called circadian rhythms;these are the same rhythms that characterize various biological activities throughout adult life!  You definitely have started to follow a pattern for your sleep and wakeful times. I love predicting when you’ll be awake.
  • Your heart can now be heard with a stethoscope. (I’m going to try this with my stethoscope at work this week!)
  • Immunities are being transferred from me to you now. These immune cells will protect you from viruses I’ve already had for up to six months after your birth!
  • The neurons for taste, smell, hearing, seeing, and touch are now developing in specialized areas of your brain. Production of your neurons slows down as existing nerve cells grow larger and make more complex connections. <–ugh I die! 🙂
  • You begin to startle in reaction to loud sounds. Amazingly, you can actually hear noises outside of the womb. Familiar voices, music, and sounds that you become accustomed to during your development stages often are calming after birth. That means you’ll have no problem with mommy talking/singing and the girls barking!
  • Your uterus is starting to develop. You now have approximately six million eggs in your ovaries. About one million will remain at birth.
  • You are about 6.46 inches and weigh around 10.58 ounces. (Remember that 16 ounces is equal to 1 pound)

Here are some pictures of what you looked like at 20 weeks:

21 Weeks Development

  • White blood cells are under production. Leukocytes (or white blood cells) form our body’s defense system. They help fight infections and diseases, and you are making them now.
  • Your skin has changed from translucent to become more opaque.
  • Your tongue is fully formed.
  • Your uterus and vagina are now formed. Unlike males, females have a limited supply of eggs in their lifetime. At this point you have 6 million eggs. This amount decreases to approximately one million by birth.
  • You swallow more this week. After you take in amniotic fluid, your body absorbs the water in the liquid and moves the rest into the large bowel. This is good practice for your digestive system!
  • Your wake and sleep periods become more consistent.
  • You are surrounded by around 320ml of amniotic fluid this week. The temperature of the fluid is maintained at a slightly higher degree than my own core temperature. This helps you to stay warm.
  • Lots of baby movements this week!
  • You are now gaining weight steadily, with fat being added to your body. Which explains some of my weight gain this week, woohoo!
  • Your bone marrow has started making blood cells, a job done by your liver and spleen until this point.
  • Your small intestine is starting to absorb sugars.
  • Your brain and muscles are working in synchronization this week which means there’s intent behind your movements now!  If I lay in a particular position and you don’t like it, you start wriggling around so you can find your own comfortable space! 😀
  • Tiny tooth buds for your permanent teeth are starting to form in your gums from this week.
  • You measure about 10.51 inches and weigh nearly 12.7 ounces.

Here are some pictures of what you look like on the inside this week!


If you haven’t read about this amazing, life-saving surgery done on a 21 week old fetus, read about it here. Incredible.

I can’t believe your little arm looks like this inside me right now. So precious and amazing.



Happy baking my love! You’re doing so well!! 3 more weeks until viability, wooho! I love you!!


About Em

After the loss of our first pregnancy, we took a much needed vacation to Costa Rica to enjoy each other and clear our minds. Well, as luck would have it, we brought home much more than great memories and great tans...our own little Costa Rican souvenir. Here is our journey!
This entry was posted in Neural development, Pregnancy. Bookmark the permalink.

2 Responses to 20 and 21 weeks development

  1. Pingback: 20 Weeks | A Sweet Souvenir

  2. Pingback: 21 Weeks | A Sweet Souvenir

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