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The joys of motherhood are never fully experienced until all the children are in bed.
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How Big is Your Baby Now?

Tracking the growth of your baby through all the stages of your pregnancy can be a fun, but sometimes mysterious, process. What’s happening inside? How big is the baby at different stages?

How Big is Your Baby Now?

Three to Four Weeks

As you know, your baby’s due date is calculated from the first day of your last menstrual period. Conception occurs about two weeks from that day, so that is when you are truly considered to be pregnant. For the purposes of aligning with the 40 weeks of pregnancy timeline, we say that sometime during the third week of pregnancy the sperm meets the egg and conception occurs. The fertilized egg or zygote then spends about six days traveling through your fallopian tubes, busily dividing and redividing in the process of becoming a blastocyt and settling into the uterus.

At this stage, weeks three and four of pregnancy, your baby is the size of a poppy seed. May women will not yet realize that they are pregnant. Although the baby is a teeny, tiny bundle of cells at this stage, the bundle is undergoing important development. It’s not too early to start taking a prenatal vitamin.

At four weeks the blastocyt is splitting into the embryo and the placenta. The neural tube, or building block of the baby’s spine is already formed, and the amniotic sac and fluid are forming into protective cushioning for the developing baby.

Five Weeks

Your embryo has grown to the size of an apple seed and is beginning to form major organs and systems.

Seven Weeks

Your baby is growing by leaps and bounds and is now the size of a blueberry. The baby’s brain is getting approximately 100 new brain cells each minute, is developing a permanent set of kidneys, and is beginning to form art and leg joints.

Nine Weeks

Your baby, which is now about the size of a green olive, has moved from being an embryo to being a fetus. The first eight weeks were spent with cells taking on different functions. Once the baby is a fetus, the development is focused on growth and development of those different functions to prepare the baby for life outside the womb.

12 Weeks

You are very likely beginning to look pregnant at this point. The baby weighs about half an ounce and is about 2.1 inches or the size of a plum. You’re nearly at the end of your first trimester and you may feel a little less like you are on an emotional roller coaster. Your morning sickness and fatigue might subside, only to be replaced by headaches and dizziness. The fetus is nearly done with developing all of its important systems and parts. At this stage you may have some genetic testing done to determine if there are any birth defects or other problems. Although these tests can be a little scary, talk with your AOA doctor to set your mind at ease and remember that it is much more likely that your baby will be fine than have any problems.

16 Weeks

Your baby is about the size of an avocado at about 4.6 inches long, and weighing in at about 3.5 ounces. He or she is big enough that your AOA physician can hear the heartbeat. At this stage you may begin to feel fluttering sensations in your abdomen, which is your baby moving around. As the baby increases in size this movement will become unmistakable, but at this stage may feel like a muscle twitch or gas. Another exciting development is that the baby is just beginning to hear your voice!

20 Weeks

You’re at the halfway point! Your baby is about the size of a banana at 6.5 inches and 10.2 ounces. There is a lot of growth still needed, but at this stage you will likely have an ultrasound and will be able to indentify the baby’s sex.

24 Weeks

At this stage your baby is about the size of a cantaloupe. Your AOA doctor will order a Glucose Tolerance Test to see if you are at risk for gestational diabetes. The baby will be kicking up a storm and you may be experiencing leg cramps, backaches, and swollen feet.

28 Weeks

You are entering your third and final trimester. Your baby is about the size of an eggplant. At this stage you may start feeling Braxton Hicks contractions. These are contractions that occur before real labor. They can be considered “practice” contractions for your body.

32 Weeks

While the delivery date still seems like it’s a ways off, both you and your baby are physically ready for birth in many ways. Your baby is now the size of a squash, weighing between 2.5 and 3.8 pounds. Your nipples may be looking darker, and your baby may have turned into the head-down position by now, in anticipation of the trip through the birth canal.

36 Weeks

Your baby is now the size of a honeydew melon. She weighs between 4.2 and 5.8 pounds and is between 17 and 19 inches long. If born now, your baby would probably be able to breathe on her own.

37 Weeks

Your baby is now the size of a winter melon at 18.9 to 20.9 inches long and weighing in at about 6 to 9 pounds. She has reached full term, which means that she’s developed her most critical functions. Over the next few weeks she’ll get even healthier and stronger.

40 Weeks

Wow! Your due date is here. Your baby is about 19-21 inches long and weighs about 6.2 to 9 pounds. You’re filled with excitement and trepidation, and it can be a bit stressful not knowing exactly when the baby will decide to come. You’ll be busy making sure all of the last minute details are taken care of and that you are ready to go when the time comes. Try to relax and remember that your body will let you know when the baby is ready to meet the world!

At every stage of your pregnancy, your AOA doctor is here to help you understand the process, to answer any questions you may have, and to alleviate your concerns. Be sure to ask all of the questions that you have and remember that your AOA physician is your partner in this process.

Learn more about your baby’s development during pregnancy: