Weeks 5 & 6 of Pregnancy: Key Developments in Early Growth

October 9, 2025

Pregnancy is an incredible journey, and the earliest weeks often bring rapid changes, both inside the pregnant woman’s body and in the developing embryo. By Weeks 5 and 6, many women begin to realize they are pregnant, often after noticing a missed period and confirming it with a pregnancy test. These two weeks mark the start of some of the most significant early developments.

Week 5: The Heart Begins to Beat

At Week 5, the embryo is approximately the size of an apple seed. Though still very small, the foundations for major body systems are forming. The neural tube, which will later develop into the brain and spinal cord, is closing¹. Around this time, the heart begins to beat and starts pumping blood through a newly forming circulatory system². This early cardiac activity is one of the first visible signs of life on an ultrasound, though it may not yet be detected in every case.

What’s happening in the body:

• Hormone levels, particularly hCG, are rising quickly¹.
• Many people experience the first signs of pregnancy, such as fatigue, nausea, sore breasts, or mood changes².
• An ultrasound performed at this stage may confirm the presence of a gestational sac and sometimes the yolk sac, which provides nutrition to the embryo in the earliest stages³.

Week 6: Rapid Growth and Facial Features Begin

By Week 6, the embryo is about the size of a sweet pea. Development is advancing quickly, and several recognizable features start to take shape. Tiny buds that will become arms and legs begin to form, while early facial features, such as the beginnings of the eyes, nose, and ears, are also starting to appear¹.

The heartbeat, which first appeared in Week 5, is now stronger and more regular². Many women who have had an ultrasound at one of our centers describe the first time they see or hear this heartbeat during an ultrasound as a moment of reassurance and hope.

What’s happening in the body:

• Pregnancy symptoms may become more noticeable due to rising hormone levels¹.
• Morning sickness, heightened sense of smell, or changes in appetite may appear³.
• The uterus is beginning to expand to make room for the growing embryo².

Why These Weeks Matter

Weeks 5 and 6 represent a critical stage of development. The embryo is rapidly forming essential organs and structures that will sustain growth throughout pregnancy. Because so much is happening at once, this stage is also when many people feel the greatest physical and emotional changes¹.

We understand that every pregnancy journey is unique. If you think you may be pregnant, or if you’re in these early weeks and want support, we’re here for you. We offer FREE pregnancy testing, ultrasounds, and a safe place to ask questions. Whether you’re feeling uncertain, overwhelmed, or simply curious about what’s happening in your body, our compassionate team is ready to walk alongside you.

📞 Call us at 610.622.9957
📧 Email: info@amnion.org
📍 Or schedule a free appointment on our website: amnionpregnancycenter.com

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