fetus or baby

During each week of pregnancy, an unborn child undergoes many changes. Let’s find some understanding to the question “Is my unborn child a fetus or a baby?” Here is a look at common medical terms to explain what happens during pregnancy. 

Understanding Pregnancy Terminology

There are two ways to date a pregnancy: Gestational Age and Fertilization Age. During these stages, an unborn child is addressed as an embryo, fetus, or baby.

Gestational Age: Gestational age is used by healthcare professionals to date pregnancy. This term refers to how long it has been since the first day of the mother’s last menstrual period (LMP). Gestational Age starts two or more weeks before the fertilization of the egg by the sperm.

Fertilization Age: Fertilization Age refers to how long it has been since conception (the fertilization of the egg by the sperm).

A healthcare provider will date a pregnancy due date 40 weeks from the first day of your last menstrual period (LMP).

What Happens To The Baby During The First Trimester?

The first trimester is from week 1 to the end of week 12, the second trimester is from week 13 to the end of 26, and the third trimester is week 27 until 40 weeks. What happens during the first trimester?

NOTE: All of the following weeks are based on Gestational Age, or LMP.

Week 4 – The baby is scientifically referred to as an embryo. The embryo is attached to the lining of the uterus. A pregnancy test can measure human chorionic gonadotropin (hCG – a pregnancy hormone made by the placenta) and confirm pregnancy.

Week 5 – Blood vessels begin to form and pump blood. The heartbeat can be seen with ultrasound. 

Week 6 – The heart beats about 90 -110 times a minute (bpm). The digestive and respiratory systems are forming.

Week 7 – The baby’s eyes begin to form. The baby begins to move around and can be seen on ultrasound ~ movement is felt between 16 and 22 weeks.

Week 8 – Now ½ of an inch long. The intestines are forming. The baby’s umbilical cord is visible. The umbilical cord supplies oxygen and nutrients to the baby.

Week 9 – The embryo has taken on a mini baby shape. The skeleton of the baby is forming and the bones are soft.

Week 10 – At this point, major parts have formed and are growing rapidly. The nervous system is more responsive. 

Week 11 – The fetus has all major organ systems. The eyelids are fully formed and closed to protect the developing eyes. The eyes will open at about 28 weeks.

Week 12 – The reflexes are forming. The baby can open and close hands and curl toes.

A baby has begun to create the foundation for important structures. Women will begin to show signs of pregnancy – the first indication of pregnancy is often due to a missed period. Other symptoms include frequent urination, nausea, fatigue, food aversion/morning sickness, and more.

Is My Unborn Child A Fetus Or A Baby?

It is normal to have questions during pregnancy! Let us look at the definitions of both fetus and baby.

Baby is defined as:

  • A very young child; an infant
  • An unborn child; a fetus
  • The youngest member of a family or group

Fetus is defined as:

  • An unborn baby that develops and grows inside the uterus
  • An unborn child is medically referred to fetus starting at eleven weeks

Have questions you need answered? Visit us at optionsforwomenrf.com/frequently-asked-questions and submit your question.

 We Are Here For You

Are you experiencing an unplanned pregnancy? Wondering what your first step should be? Feeling alone? We are here for you.

Women can meet with a medical professional or caring Client Advocate. Clients are welcome to bring a support person with.

At Options for Women / River Falls, you have access to no-cost pregnancy testing, ultrasound, Sexually Transmitted Infections testing, medically accurate information to your pregnancy options, and practical support.

Visit us online at optionsforwomenrf.com to learn how we can help you. We are a free and confidential Sexual Health Clinic located on main street in River Falls, Wisconsin. Call us at 715-425-8539 to learn more about how we can help you or schedule your appointment online.


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