17 and 18 weeks develoment

Hi baby girl!

You are growing up a storm and I missed your 17 weeks post last week so I’m combining that one with this week’s 18 week development. I LOVE reading about the various changes you’re going through and how you’re growing. I hope you’re this excited by biology too…we’re going to have a blast learning together! Okay, here we go…

By 17 weeks stem cells arrive and multiply in your bone marrow.Most of your blood cell formation will eventually occur here!

In the respiratory system, the bronchial tree is now nearly complete.All airways contain smooth muscle and nerve bundles.

Your pancreas now begins producing glucagon, which is an important hormone that prevents blood sugar levels from dropping dangerously low. Your body is preparing to begin regulating itself! You’re not going to need my help, very soon here!

The umbilical cord is growing thicker and stronger.

At 17 weeks you weighed just over 5 ounces.

At 17 weeks you were about 5 inches long crown to rump and would be about 9 inches head to toe, if you could stretch out.

Your retina has become sensitive to light.

Your first stools (meconium) are now beginning to accumulate.

You are able to recycle your amniotic fluid by swallowing up to a liter a day! 

Fat stores begin to develop under your skin at 17 weeks. The fat will provide energy and help keep you warm after birth! 

Your skeleton is transforming from cartilage to bone. But not to worry, your bones remain flexible to make the journey through the birth canal easier.

Here are some pictures from your 17 week development:

18 Weeks:

The retina in your eye now has discrete layers.

The vast majority of neuron multiplication in your brain is complete by 18 weeks! Now it will be all about refinement and connections! Also, you are sporting some myelin around those axons! Myelin helps conduct messages in your brain faster and helps focus the signal.

In your teeth, enamel begins to develop between 18 and 22 weeks.

By 18 weeks, you are now starting to produce many of the same hormones found in adults. For example, painful procedures trigger a hormonal stress response. As in newborns and adults, pain is followed by the release of cortisol, ß-endorphins, and norepinephrine into the blood stream.

This week, you are now 6 inches long and weigh 7 ounces! Big girl!! 🙂

You can hear sounds and may be startled by loud noises. <– I startled you this weekend yelling at the dogs…sorry sweetie!

You now have recognizable active and rest periods.

Your skin is building a protective wax layer (vernix). Vernix (a white cheese like protective material) is forming on your skin with the lanugo, a soft lightly pigmented hair covering your body and limbs, both help to protect your skin during your months in water. You can hear my heart beating, my stomach rumbling and our blood moving through the umbilical cord!

Tiny air sacs called alveoli begin to form in your lungs and your vocal chords are now formed. I read that you actually go through the motions of crying but without air you don’t make a sound, yet

Your precious heart is pumping 25 quarts of blood a day. Simply astonishing.

Here are your 18 week pictures!

And my favorite for the week — This is an actual live baby at 18 weeks gestation taken in 1965, using an endoscopic camera and a flash! Hi baby!!! So perfect!


I love you so much sweet girl! We have your anatomy scan coming up very soon and I’m so excited to be able to see you again! Until then, stay warm and happy!

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 17 and 18 weeks develoment

  1. Pingback: 17 weeks | A Sweet Souvenir

  2. Pingback: 18 weeks | A Sweet Souvenir

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