Fetal Development: 5-40 Weeks

July 5, 2022

A baby in the womb experiences so many changes throughout the 40 weeks of pregnancy.  From conception to labor, your baby is constantly growing and developing.  It’s hard to believe, but these changes can be noticed as early as 5 weeks.  Let’s take a look at some of the milestones that occur throughout those 40 weeks. Use this timeline to learn how big your baby is, plus how they’re developing throughout pregnancy.

5 Weeks:

  • Your baby’s brain and spinal cord have begun to form.
  • The heart begins to form.
  • Arm and leg buds appear.
  • Your baby is now an embryo and one-twenty-fifth inch long.


8 Weeks:

  • All major organs and external body structures have begun to form.
  • Your baby’s heart beats with a regular rhythm.
  • The arms and legs grow longer, and fingers and toes have begun to form.
  • The eyes have moved forward on the face and eyelids have formed.


12 Weeks:

  • The nerves and muscles begin to work together. Your baby can make a fist.
  • The external sex organs show if your baby is a boy or girl.
  • Eyelids close to protect the developing eyes. They will not open again until the 28th week.
  • Head growth has slowed, and your baby is much longer. Now, at about 3 inches long, your baby weighs almost an ounce.


16 Weeks:

  • Muscle tissue and bone continue to form, creating a more complete skeleton.
  • Skin begins to form. You can nearly see through it.
  • Your baby makes sucking motions with the mouth (sucking reflex).
  • Your baby reaches a length of about 4 to 5 inches and weighs almost 3 ounces.


20 Weeks:

  • Your baby is more active. You might feel slight fluttering.
  • Eyebrows, eyelashes, fingernails, and toenails have formed. Your baby can even scratch itself.
  • Your baby can hear and swallow.
  • Now halfway through your pregnancy, your baby is about 6 inches long and weighs about 9 ounces.


24 Weeks:

  • Taste buds form on your baby’s tongue.
  • Footprints and fingerprints have formed.
  • Real hair begins to grow on your baby’s head.
  • The hand and startle reflex develop.
  • Your baby sleeps and wakes regularly.
  • Now at about 12 inches long, your baby weighs about 1½ pounds.


32 Weeks:

  • Your baby’s bones are fully formed, but still soft.
  • Your baby’s kicks and jabs are forceful.
  • The eyes can open and close and sense changes in light.
  • Lungs are not fully formed, but practice “breathing” movements occur.
  • Your baby is gaining weight quickly, about one-half pound a week. Now, your baby is about 15 to 17 inches long and weighs about 4 to 4½ pounds.


37-40 Weeks:

  • At 39 weeks, your baby is considered full-term. Your baby’s organs are ready to function on their own.
  • As you near your due date, your baby may turn into a head-down position for birth. Most babies “present” head down.
  • At birth, your baby may weigh somewhere between 6 pounds 2 ounces and 9 pounds 2 ounces and be 19 to 21 inches long. Most full-term babies fall within these ranges. But healthy babies come in many different sizes.


It is truly fascinating to watch how so much change and growth can happen from milestone to milestone. At Options Health, we offer programs and services to help you throughout the process. For new and expecting moms, we have a wonderful program called Earn While You Learn (EWYL).  EWYL is a free program that provides education, emotional support, and material resources. Once enrolled in EWYL, you will be connected with a mentor to guide you through an amazing curriculum of parenting classes where you earn credits to be spent in our Care Closet; where you can get diapers, wipes, baby clothes, baby furniture, and more!

Is the father of the baby involved? If so, we have an awesome program for him too! FIT (Fathers In Training) is a free program that will challenge him to be the best father he can be by walking alongside him through our skill-building classes and mentorship.

If you are interested in either of these free programs, please contact us today!

If you think you are pregnant, call us or text us to schedule an appointment for a free pregnancy test. The pregnancy tests offered by Options Health are lab-grade urine tests, providing you with instant results. After your pregnancy test, our nurse and your patient advocate will chat with you and review the results in a private setting. Depending on the result of your pregnancy test, we may recommend a free limited obstetric ultrasound. The ultrasound exam will assess the viability of your pregnancy and ensure the pregnancy is in the uterus (non-ectopic, which could potentially be life-threatening), and determine how far along in your pregnancy you are, as well as the gestational age of the baby. Your patient advocate will also review all of your pregnancy options, including the risks, side effects, and procedure of abortion.

Options Health is a safe place where you can confidentially come and discuss sexual health, pregnancy, and relationship issues with one of our patient advocates.  Feel free to contact us today to take advantage of our free services, including pregnancy testing, ultrasound, pregnancy options consultation, STD testing, and abortion aftercareCall us or text us to schedule an appointment. We are here for you and ready to listen!


Source: https://www.womenshealth.gov