Fetal Development by Week

Within 24 hours of your egg being fertilized, long before you even knew you were pregnant, your baby already began to form. From a cluster of cells, to an embryo, to a fetus - your baby grows rapidly throughout your entire pregnancy. Each week of pregnancy is marked by remarkable development and some pretty amazing milestones. Read on as we go through the different stages of fetal development week by week.

Week 1-4: The Beginning

Fun fact: roughly the first two weeks of pregnancy are in the books before you are even technically pregnant. As strange as it sounds, weeks 1-2 of pregnancy occur before ovulation. Let’s unpack that a little. With each monthly cycle comes a period of time where your body gears up to host a child. Hormones build up while your uterus prepares for pregnancy. Then, one of two things happen: you get pregnant, or you get a period. By the time you were to ovulate and get pregnant, you’re already headed into week 3 of pregnancy. Week 4 is typically when implantation occurs and the beginnings of a placenta starts to form. By the end of week 4, your itty-bitty babe is roughly the size of a poppy seed.

(1)

Week 5-8: The Formation of Vital Organs

Thanks to hormones in overdrive as the second month of pregnancy begins, week 5 may be around the time you first discover that you are pregnant. This week is also when your baby’s heart begins to form. It will beat an average of 110 beats per minute by the end of week 5. Week 6 is marked by primitive facial structures such as their eyes, ears, and mouth beginning to form. During week 7-8, your baby develops tiny arm and leg buds with webbed hands and feet. All body systems and major organs are developing rapidly in the second month of pregnancy. While they may resemble a tadpole this month, week 8 holds a pretty big milestone. Your embryo is now a fetus.

(1)

Week 9-12: Physical Features Become Evident

As month 3 begins, those primitive facial structures are beginning to look alot more human-like. Although your baby’s head is still roughly 50% of their total length, all physical features are becoming evident. Limbs, bones, muscles, and organs are developing rapidly this month. Your baby even has tiny teeth and taste buds forming by week 9! Those webbed fingers and toes are gone by week 10 as fingernails and toenails begin to take shape. Before the end of month 3, your baby will be busy drinking amniotic fluid and exploring the world around them. Any risk of miscarriage has dropped drastically by the end of week 12 thanks to all the critical development that has taken place.

(1)

Week 13-16: Rapid Growth and Development

Month 4 of pregnancy is pretty remarkable. Your baby is growing at an impressive speed and you might even begin to feel movement this month, especially if this isn’t your first baby. Your doctor can now hear your little one’s heart beat on a doppler and your bump will soon be apparent, if it isn’t already. Your baby is busy growing too - their skin becomes less translucent and they even begin to develop some hair. By week 14, your baby’s genitals are fully formed and they may be apparent on an ultrasound by week 16. Your baby can hear you this month, too!

(1)

Week 17-20: Sensory Development and Gender

While genitals have been developed for a couple of weeks now, most doctors are confident in predicting the sex of your baby by week 17 or 18. This may be your first opportunity to see your baby on an ultrasound. What you may see is thumb sucking, yawning, and you may even catch a smile if you’re lucky! Your baby’s brain is developing rapidly, including the area that is responsible for sensory development. Fetuses typically weigh about 1 pound by the end of week 20.

(1)

Week 21-24: Viability Outside the Womb

Month 6 is marked by a pretty amazing milestone - viability outside the womb! Babies who are born after the 23rd week of pregnancy stand a chance of survival, thanks to modern medicine. Lungs are fully developed by the end of the fifth month, but not mature enough to work on their own outside of your womb.

(1)

Week 25-28: Continued Growth and Fat Accumulation

Your baby will really be packing on the pounds this month, literally, pounds. If you were to get an ultrasound this month, you would notice significantly chubbier cheeks. You may also notice that your baby can blink and now has eyelashes. Your baby might weigh as much as 3 pounds by the end of week 28.

(1)

Week 29-32: Respiratory and Bone Development

While respiratory and bone development are impressive this month, brain development is in overdrive. You may notice your baby responding to more external stimuli such as bright lights and loud noises. With the exception of their lungs and their brain, all of your baby’s other organs are essentially ready to operate in the world outside of your womb.

(1)

Week 33-36: Preparing for Birth

Almost there - your baby is gearing up for birth this month. Your baby will likely be head down and ready to descend by week 33. Their bones continue to harden, with the exception of their skull. This needs to remain soft in order to squeeze through the birth canal. Your baby’s skin is coated in a thick, waxy substance called vernix to protect their skin from birth and its first few days outside of the womb.

(1)

Week 37-40: The Final Stretch

This is it! You could go into labor at any point this month. In fact, anything after 38 weeks is considered full term. You may feel more pressure in your pelvis this month as your baby descends in preparation for their grand arrival. Your baby is growing rapidly at an average of .5 pounds per week this month. Keep an eye out for signs of labor and get ready to snuggle that newborn soon!

(1)

Conclusion

All that growing was exhausting! Once that sweet baby is in your arms, you can count on Dreamland Baby to help you both get the sleep you need from birth and beyond!