Week 4

Embryo cell stages

Published : 18/04/2024

Last updated: 03/05/2024

Welcome to week 4 of the pregnancy journey! This week, your little bun in the oven is starting to make its presence known. It’s like having a tiny tenant moving in, as the embryo continues to grow and develop at a rapid pace. You might start noticing some subtle changes in your body, like heightened senses and maybe even a touch of morning sickness.


It’s all part of the miraculous process of creating new life. So get ready to embrace the journey ahead, complete with its ups, downs, and everything in between. You’re in for an adventure like no other!

Highlights of week 4

You’re in your first month of pregnancy
You have 36 weeks to go
You’re in the first trimester
Your baby is about the size of a poppy seed

Your body at 4 weeks pregnant

At this point, you don’t yet know that you are pregnant, so you are still trying to conceive. Week four of pregnancy is very exciting. Your fertilized egg will implant itself into your uterus and become an embryo. Once that happens, your body will begin gestating and growing an embryo, and later a fetus. The cells responsible for pregnancy form a hormone known as hCG. This hormone stops menstruation. By the end of this week, an at-home pregnancy test may even be able to detect your pregnancy.


Fun fact: Those pregnancy test kits we buy from drug stores actually try to find the presence of the hCG hormone. If this hormone is found, it gives a positive result.

Your Unborn Baby’s Size at 4 Weeks

At the beginning of week four, implantation takes place. But before implantation occurs, a few other things have to happen. The whole process started only five to six days ago when your egg was fertilized by sperm. At that point, your fertilized egg became a zygote and underwent rapid cell division and multiplication. It also journeyed through the fallopian tube, where it reached the next stage of development—a blastocyst.


Once it reaches the uterus, it implants itself into the uterine lining. At this time, it’s about 0.014 to 0.04 inches and less than 0.04 ounces. So tiny!

The blastocyst develops into layers of cells, some that will become an embryo and some that will become the placenta. An early amniotic sac is also developing. The placenta is what produces a hormone called human chorionic gonadotropin (hCG), which is what at-home pregnancy tests detect.

Embryo Developmental Milestones at 4 Weeks

Your baby starts off as a blastocyst during most of this week. But by the end of week four, around 10 to 12 days after conception, it becomes an embryo – a big milestone!


During this early stage of development, the baby’s cells begin to form three main layers:


  1. Inner layer: This layer starts to shape the respiratory and digestive systems.
  2. Middle layer: Here’s where the heart, muscles, bones, and blood vessels begin to form.
  3. Outer layer: This layer eventually becomes the brain, skin, and nervous system.

Pregnancy Symptoms at Week 4

No pregnancy symptoms?

Hey there, if you’re in week 4 of your pregnancy and not feeling any symptoms yet, don’t sweat it. It’s totally normal! Lots of women don’t feel much at this stage. Typically, symptoms start kicking in around week 6.

But if you are feeling something, here’s what you might experience:


Tender, swollen breasts:

Your breasts might feel sore and tender. They could even grow a bit, and your nipples might darken. Plus, you might notice some prominent veins on your breasts.



Feeling super tired? You’re not alone. Many pregnant women feel exhausted in the first trimester, thanks to a surge in progesterone.


Nausea or vomiting:

Morning sickness isn’t just for mornings—it can hit any time of day. Usually, it starts around week 6, but some women feel it as early as week 4. Fun, right?


Gas and bloating:

Blame it on the hormones! Increased progesterone can slow down your digestion, leaving you feeling gassy and bloated. You might even find yourself burping or passing gas more often.



Don’t panic if you feel some cramps—they’re often nothing to worry about. It could be implantation cramps as the fertilized egg settles in your uterus. But if cramps come with bleeding, it’s best to call your doctor.


Mood swings:

Hormones are running wild, so it’s no surprise if you’re feeling a bit emotional. Mood swings are totally normal, especially in the first trimester. Just keep an eye on them—if they start getting intense or last more than a couple of weeks, chat with your provider.

Remember, it’s still early days, and you might not notice much yet. But if you’re curious, a pregnancy test is the way to go to know for sure.

Tips for Week 4


Many people thinks that they should avoid
exercise during pregnancy, which is wrong. It is actually helpful for mother and the baby. Exercise boosts your mood, energy, and reduces stress, which can help to stay active. It reduces the risk of Cesarean section.


Avoid smoking and smokers

Staying near smoking damages the fetus very severely. So don’t go near a smoker. So if anybody smokes in your family, then talk to them.


Taking Vitamin D and Folate

The two most vital elements during pregnancy and for a healthy fetus. Only foods may not be sufficient to supply the required amount needed for a pregnant body. Then you have to take supplements, your health care provider will measure the amount needed for you, after seeing your test reports.


Prenatal Tests and Doctor’s Appointments

If you get a positive pregnancy test by the end of this week, you can schedule your first appointment. Typically, the first prenatal appointment is scheduled for when you are 8 to 10 weeks pregnant, though it may vary based on your medical history.

Despite not having appointments, you can contact your healthcare provider for any questions or concerns, especially if you experience heavy bleeding or cramping after a positive test.

It’s advisable to note down any non-urgent questions about pregnancy for discussion. It can be helpful because it’s easy to forget your questions when you are in the thick of an appointment.

You might consider talking to your provider about any concerns you have about your symptoms, what pregnancy testing might be recommended for you, and thoughts about where you’d like to give birth.

A Gentle Nudge from Mammas Journey

This is the time when both partners are unaware that they are soon-to-be parents. However, since you are planning to be, both of you should maintain a healthy and balanced lifestyle. This includes eating healthily, quitting smoking and drinking alcohol, and exercising regularly.


Although the journey to parenthood may begin with the excitement of conception, it’s important to remember the responsibilities that come with it. By adopting healthy habits early on, both partners can ensure the best possible start for their future family.

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