Week 4 of Pregnancy
Your baby is the size of a chia seed
0.1 in
Baby Development
The ball of cells has now developed into a **blastocyst** and has reached the uterus. It begins the critical process of **implantation**, burrowing deep into the nutrient-rich lining of your uterus. This is a major milestone, as it establishes a physical connection with you that will last for the entire pregnancy. The blastocyst has two distinct parts: the inner cell mass, which will become the embryo, and the outer layer, which will form the placenta.
Once implanted, the outer cells begin to produce the hormone hCG, which is essential for maintaining the pregnancy. The amniotic sac, a watertight membrane, also starts to form around the blastocyst. This sac will fill with amniotic fluid, providing a protective, cushioned environment for your baby to grow in for the next several months. By the end of this week, your baby is the size of a poppy seed.
Your Body This Week
This is the week you officially miss your period. The rising levels of hCG signal to your body that you are pregnant, preventing your next menstrual cycle. You might experience some light cramping or spotting as the blastocyst implants into your uterine wall; this is known as implantation bleeding. It's often lighter and shorter than a normal period.
The hCG hormone is now detectable in your urine, meaning a home pregnancy test will likely show a positive result. While some early pregnancy symptoms like fatigue or breast tenderness might begin to appear, many women still feel completely normal at this stage. Your body is just beginning the immense task of supporting a new life.
Milestones This Week
Positive pregnancy test!
This week, the pregnancy test can usually show a positive result. Congratulations!
Find a healthcare provider
It's important to start prenatal care as early as possible. Find an obstetrician or health unit.
Learn More
At Week 4 of your pregnancy, significant hormonal and physiological changes are underway, though they may not always be accompanied by pronounced symptoms. One of the earliest signs you might notice is breast tenderness, caused by an increase in hormones like estrogen and progesterone, preparing your body for what's to come. While your overall caloric needs haven't changed yet, your body is already becoming more efficient at storing nutrients to support your developing baby. This week is more about nutrient-rich choices rather than eating more calories. Focus on incorporating a variety of fruits, vegetables, whole grains, lean proteins, and healthy fats into your diet to provide essential nutrients for both you and your baby. Some might experience morning sickness, for which small, frequent meals and foods containing ginger may offer relief. Additionally, staying hydrated is crucial, as it supports your increasing blood volume and overall health. If you're feeling fatigued, remember that it's perfectly normal due to the hormonal changes taking place. Listen to your body and incorporate light physical activities like walking or prenatal yoga when you feel up to it. Finally, even if you're not experiencing symptoms, ensuring early and consistent prenatal care is vital to confirm the pregnancy's progress and set you up for a smooth journey ahead.
Frequently Asked Questions
How big is my baby at 4 weeks pregnant?
At week 4 of pregnancy, your baby is about the size of a chia seed, measuring approximately 0.1 in.
What trimester is week 4 of pregnancy?
Week 4 is in the first trimester of pregnancy. The first trimester covers weeks 1-13, the second trimester covers weeks 14-26, and the third trimester covers weeks 27-40.
What is happening with my baby at week 4?
The ball of cells has now developed into a **blastocyst** and has reached the uterus.
What symptoms can I expect at week 4 of pregnancy?
This is the week you officially miss your period.
Track your pregnancy journey
Get personalized daily updates, tips, and milestone tracking with BabyLingo
