Slideshow: Fetal Development Month by Month
Conception
Fertilization happens when a sperm meets and penetrates an egg. It's also called conception. At this moment, the genetic makeup is complete, including the sex of the baby. Within about three days after conception, the fertilized egg is dividing very fast into many cells. It passes through the fallopian tube into the uterus, where it attaches to the uterine wall. The placenta, which will nourish the baby, also starts to form.
Development at 16 Weeks
The baby now measures about 4.3 to 4.6 inches and weighs about 3.5 ounces. You should be able to feel the top of your uterus about 3 inches below your belly button. The baby's eyes can blink and the heart and blood vessels are fully formed. The baby's fingers and toes have fingerprints.
Development at 20 Weeks
The baby weighs about 10 ounces and is a little more than 6 inches long. Your uterus should be at the level of your belly button. The baby can suck a thumb, yawn, stretch, and make faces. Soon -- if you haven't already -- you'll feel your baby move, which is called "quickening."
Time for an Ultrasound
An ultrasound is usually done for all pregnant women at 20 weeks. During this ultrasound, the doctor will make sure that the placenta is healthy and attached normally and that your baby is growing properly. You can see the baby's heartbeat and movement of its body, arms, and legs on the ultrasound. You can usually find out whether it's a boy or a girl at 20 weeks.
Shown here is a 2D ultrasound (inset) contrasted with a 4D ultrasound, both at 20 weeks.
Development at 28 Weeks
The baby weighs about 2 pounds, 6 ounces, and changes position often at this point in pregnancy. If you had to deliver prematurely now, there is a good chance the baby would survive. Ask your doctor about preterm labor warning signs. Now is the time to register for birthing classes. Birthing classes prepare you for many aspects of childbirth, including labor and delivery and taking care of your newborn.
Development at 32 Weeks
The baby weighs almost 4 pounds and is moving around often. The baby's skin has fewer wrinkles as a layer of fat starts to form under the skin. Between now and delivery, your baby will gain up to half his birth weight. Ask your doctor how to do a fetal movement chart. Think about breastfeeding. You may notice a yellowish fluid leaking from your breasts. That is colostrum, and it happens to get your breasts ready for making milk. Most women go to the doctor every two weeks at this stage of pregnancy.
Development at 36 Weeks
Babies differ in size, depending on many factors, such as gender, the number of babies being carried, and size of the parents. So your baby's overall rate of growth is as important as the actual size. On average, a baby at this stage is about 18.5 inches and weighs close to 6 pounds. The brain has been developing rapidly. Lungs are nearly fully developed. The head is usually positioned down into the pelvis by now. Your baby is considered at 'term' when he is 37 weeks. He is an early term baby if born between 37-39 weeks, at term, if he's 39-40 weeks and late term if he's 41-42 weeks,
Birth!
A mother's due date marks the end of her 40th week. The delivery date is calculated using the first day of her last period. Based on this, pregnancy can last between 38 and 42 weeks with a full-term delivery happening around 40 weeks. Some post-term pregnancies -- those lasting more than 42 weeks -- are not really late. The due date may just not be accurate. For safety reasons, most babies are delivered by 42 weeks. Sometimes the doctor may need to induce labor.
Reviewed by Dan Brennan, MD on October 09, 2014
IMAGES PROVIDED BY:
(1) Copyright © LookatSciences / Phototake – All rights reserved.
(2) Dr. David M. Phillips / Visuals Unlimited / Getty Images
(3) 3D4Medical.com / Getty Images
(4) Copyright © Scott Camazine / Phototake -- All rights reserved.
(5) Copyright © LookatSciences / Phototake – All rights reserved.
(6) Nestle / Petit Format / Photo Researchers, Inc.
(7) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(8) a) Dr.Benoit/Mona Lisa. Copyright © LookatSciences / Phototake -- All rights reserved. b)Vincenzo Lombardo / Photographer's Choice / Getty Images
(9) Dr. Benoit/Mona Lisa. Copyright © LookatSciences / Phototake -- All rights reserved.
(10) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(11) Jose Manuel Gelpi Diaz / iStockphoto
(12) © Lennart Nilsson Photography AB. All rights reserved worldwide.
(13) © Yoav Levy / Phototake -- All rights reserved.
SOURCES:
American Academy of Family Physicians.
American College of Obstetricians and Gynecologists: "How Your Baby Grows During Pregnancy."
KidsHealth.org: "Pregnancy Calendar."
March of Dimes: "Prenatal Care – Ultrasound."
US Department of Health and Human Services Office of Women’s Health: "Pregnancy: Breast Changes."
This tool does not provide medical advice. See additional information:
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
© 2014 WebMD, LLC. All rights reserved.
WebMD Slideshows
View our slideshows to learn more about your health.
-
Psoriasis in Photos See what each type looks like.
-
Foods for Focus Eat these to help you stay on task.
-
Multiple Sclerosis Warning signs to watch out for.
-
Attention Killers What steals your concentration?
-
Binge Eating Food, guilt & depression.
Advertisement
Health Solutions From Our Sponsors
©2005-2015 WebMD, LLC. All rights reserved.
WebMD does not provide medical advice, diagnosis or treatment. See additional information.