This week can be an anxious and exciting time, as it may be the week that you can take a pregnancy test. If you discover that you’re pregnant, you’ll technically be 4 weeks pregnant. This is because your gestational age is calculated from the first day of your last period (in comparison, the fetal age is calculated from fertilization).
You’re no doubt full of questions about the changes happening to your body and your newly growing baby. While it’s still very early days, it can be reassuring to know about the symptoms to look out for and how you might feel at this stage. Keep reading to learn about early pregnancy symptoms and get some advice from a Flo expert about what else to expect at 4 weeks pregnant.
Your baby at 4 weeks pregnant
Even though they’re only the size of a poppy seed, amazingly, this week your baby is starting to form lungs. By 26 weeks, their lungs will be able to inflate and deflate. However, they won’t be able to function fully by themselves until 36 weeks.
Benefitting from a growing placenta
Your baby is also benefiting from your growing placenta when you’re at 4 weeks. This will be fully formed by 12 weeks, although it will keep growing throughout your pregnancy. From 12 weeks onward, it will take over the transfer of nutrients to your baby. For now, your baby is getting most of their nourishment from a tiny yolk sac. This might sound strange, so let us explain. Essentially, the yolk sac is a structure outside of the baby, located within the surrounding gestational sac in the uterus. The yolk sac delivers nutrients from you to your growing baby, produces cells that turn into important structures, and circulates gasses between the two of you. Clever, huh?
How big is a baby at 4 weeks?
Length (crown to rump): Around 0.08 in. (2 mm)
Weight: Too small to calculate accurately
All measurements are approximate and vary within the normal range.