Full 40-Week Fetal Development Calendar




Get Access to Support, Benefits, and Resources for Expecting Parents. Join the EPAOA Community for FREE!



Weeks 1 & 2:  The first two weeks of a pregnancy encompass the gestational period after conception occurs, which creates a two-week variance between what is referred to as the gestational age and the fetal age.  The weekly tracking of the fetal age begins at week 3 of the gestational age.  During the gestational period of the pregnancy, the menstrual cycle for the woman has ended, and her body is preparing for ovulation.  Typically, ovulation will begin approximately 11-21 days after the first day of the last menstrual cycle.

During intercourse, several hundred million sperm are released into the vagina, which travel through the woman’s cervix and into her fallopian tube.  If conception occurs, a sperm will penetrate the egg that is in the fallopian tube, creating a single set of 46 chromosomes that are referred to as a zygote.  The zygote represents the basis for a new human being!  The fertilized egg then begins traveling toward the uterus through the fallopian tube, which takes a couple of days.  The fertilized egg, which is dividing into cells and is now referred to as a morula, will eventually end up in the uterus, at which point it is referred to as a blastocyst.  Approximately 6-12 days after conception, the blastocyst will imbed itself into the lining of the uterus, where it will begin the embryonic stage of the pregnancy.

Week 3:  During this week of your pregnancy, which is approximately 1 week after conception, the embryo is experiencing extensive phases of basic development.  The four major systems being impacted at this point are the initial development of the heart, the brain, the spinal cord, and the gastrointestinal tract.

Weeks 4 & 5:  During this week of your pregnancy, which is approximately 2-3 weeks after conception, the heart is now beating with a steady rhythm.  Leg buds and arm buds are visible, but they are not clearly distinguishable at this stage.  The formation of the placenta is occurring, and important hormones, such as hCG, are being produced.  The main vessels of the embryo are receiving a rudimentary supply of blood, and the early structures that will eventually develop into the ears and eyes are beginning to form.  The embryo is approximately ¼ of an inch in length by the end of this stage of the pregnancy.

Week 6:  During this week of your pregnancy, which is approximately 4 weeks after conception, webbed structures are present on the hand and feet buds that will eventually develop into the fingers and toes.  Other structures that are beginning to develop are the jaw, the nose, the palate, and the lungs.  At this stage, the brain is continuing its development, and the formation of the complex components of the brain has started.  It is possible that an audible heartbeat could be detected through the use of a vaginal ultrasound.  The embryo is approximately ½ of an inch in length by the end of this stage of the pregnancy.

Week 7:  During this week of your pregnancy, which is approximately 5 weeks after conception, the formation of all of the essential organs of the body has begun, even though the overall embryonic weight is quite small.  This stage is marked by the development of hair and nipple follicles, and the formation of the tongue and eyelids has started.  As the trunk begins to straighten, the toes and elbows become more visible.

Week 8:  During this week of your pregnancy, which is approximately 6 weeks after conception, the external and internal development of the ears is progressing.  All of the structures of the body of an adult human are now present in the small embryo.  The formation of some of the skeletal structure has begun, and the accompanying muscles can contract.  The various facial features are continuing their maturation, and the eyelids are further developed.  This stage of the pregnancy marks the end of the embryonic period and the beginning of the fetal period.  The embryo is approximately one inch in length by this stage of the pregnancy, and is roughly the size of a bean.

Weeks 9 - 14:  During this stage of your pregnancy, which is approximately 7-12 weeks after conception, the fetus has grown to approximately 3 inches in length and weighs about one ounce.  Even though the genitalia have clearly formed into female or male, it would not be possible to clearly distinguish them on an ultrasound.  At this stage of the pregnancy, the eyelids have closed, and they will remain closed until approximately Week 28.  The head represents nearly half of the overall size of the fetus, the buds for the development of baby teeth are present, and the fetus can make a fist.

Week 15:  During this week of your pregnancy, which is approximately 13 weeks after conception, the bones of the baby’s skeleton are starting to develop.  Your baby is growing rapidly, and the developing skeleton should soon become visible on the ultrasound images.  At this stage of the pregnancy, the scalp hair pattern on the baby is starting to form.

Week 16:  During this week of your pregnancy, which is approximately 14 weeks after conception, the eyes of the baby have started to face forward and are slowly beginning to move.  The ears are also moving toward what will be their final position, and facial expressions are possible.  The facial muscles are starting to become more developed, and expressions such as frowning and squinting can be noted.  Your baby may also be able to make sucking motions with his or her mouth at this stage of the pregnancy.  
The movements of the baby are becoming more coordinated and may be able to be seen during the ultrasounds, however, they may be too slight at this point to be actively felt by the mother.  Your baby may be more than 4 1/2 inches (120 millimeters) long from crown to rump and weigh nearly 4 ounces (110 grams) at this stage of the pregnancy.

Week 17:  During this week of your pregnancy, which is approximately 15 weeks after conception, the primary developmental feature is the production of fat stores that are beginning to develop under the baby’s skin.  This fat is necessary for the provision of energy, and will serve to warm the baby after it has been delivered.

Week 18:  During this week of your pregnancy, which is approximately 16 weeks after conception, the final position of the ears on either side of the head are noticeable.  The initial stages of hearing are developing for the baby, as the nerve endings between the ears and the brain are becoming established.  At this stage of the pregnancy, your baby may be able to hear the sounds of your bodily functions, such as your heartbeat, the rumbling in your stomach, or the sound of the blood flowing through the umbilical cord.  It may also be possible that these new sounds are startling to the baby!  Your baby may be more than 5 1/2 inches (140 millimeters) long from crown to rump and weigh 7 ounces (200 grams) at this stage of the pregnancy.

Week 19:  During this week of your pregnancy, which is approximately 17 weeks after conception, the baby’s hearing is continuing to improve.  It is possible that the baby may start to hear conversational voices outside of the womb, however, it is likely that the surrounding bodily noises and the natural protective paste that has developed over the baby’s ears will limit the clarity of what is heard!  For girls during Week 19, the formation of the vagina and uterus may have started.

Week 20:  During this week of your pregnancy, which is approximately 18 weeks after conception, you have officially reached the halfway point!   The delicate skin of the baby is covered with coating of vernix caseosa, which often resembles a greasy, cheese-like substance.  At this stage of the pregnancy, the mother may begin to feel the first movements of the baby, which is commonly referred to as the “quickening.”  Your baby may be more than 6 1/3 inches (160 millimeters) long from crown to rump and weigh more than 11 ounces (320 grams) at this stage of the pregnancy.

Week 21:  During this week of your pregnancy, which is approximately 19 weeks after conception, the primary developmental feature is the gaining of more weight by the baby.  The physical activity levels of the baby are increasing, and the baby has started to swallow.

Week 22:  During this week of your pregnancy, which is approximately 20 weeks after conception, the entire body of the baby is covered by lanugo, which is a fine, down-like coating of hair.  The purpose of the lanugo is to help the layer of vernix caseosa adhere to the skin.  It may be possible to see the baby’s eyebrows on ultrasound images.  Your baby may be more than 7 1/2 inches (190 millimeters) long from crown to rump and weigh 1 pound (460 grams) at this stage of the pregnancy.

Week 23:  During this week of your pregnancy, which is approximately 21 weeks after conception, the skin of the baby is more translucent than before, far more wrinkled, and appears to be either red or pink in color.  The movements of the eyes are becoming more rapid, and taste buds are starting to develop on the tongue.  The baby is also starting to form footprints and fingerprints at this stage of the pregnancy.   For girls, the ovaries and uterus are developed and in place, complete with an egg supply that will last a lifetime.  For boys, the testes have developed, and they are beginning to start their descent from the abdomen.  

Week 24:  During this week of your pregnancy, which is approximately 22 weeks after conception, the baby is starting to develop a regular cycle of waking and sleeping.  The presence of a real hair is becoming noticeable on the head.  Your baby may be more than 8 inches (210 millimeters) from crown to rump and weigh more than 1 1/3 pounds (630 grams) at this stage of the pregnancy.  It should be noted that, with intensive medical care, babies born at this stage of the pregnancy may be able to survive.

Week 25:  During this week of your pregnancy, which is approximately 23 weeks after conception, the hands of the baby have fully developed, however, it should be noted that all of the nerve connections to the hands are still developing.  The mother may notice that exploration of the uterus has become an enjoyable task for the baby, as activity and movement levels have markedly increased by this stage of the pregnancy.  

Week 26:  During this week of your pregnancy, which is approximately 24 weeks after conception, the fingernails on the baby’s hands have developed.  There is also a significant level of development in the baby’s lungs.  The lungs are starting to produce a substance called surfactant, which serves to allow the air sacs of the lungs to inflate, while keeping them from sticking together and collapsing when they deflate.  Your baby may be more than 9 inches (230 millimeters) long from crown to rump and weigh nearly 2 pounds (820 grams) at this stage of the pregnancy.

Week 27:  This week of your pregnancy, which is approximately 25 weeks after conception, marks the end of the second trimester.  The primary developmental feature is the continuing maturation of the baby’s liver, lungs, and immune system.  The baby has also experienced an extensive growth spurt by this stage of the pregnancy, with the measurement from crown to rump having possibly tripled since the measurements that were noted in Week 12.

Week 28:  During this week of your pregnancy, which is approximately 26 weeks after conception, the eyelashes have formed and your baby’s eyelids are partially open.  The baby is continuing to gain weight, and this gain is serving to help smooth out some of the wrinkles that are present on the skin.  Your baby may be more than 10 inches (250 millimeters) long from crown to rump and weigh nearly 2 ¼ pounds at this stage of the pregnancy.  Generally healthy babies that are born at this stage of the pregnancy have a 90% survival rate without neurological or physical impairment – and the survival rate odds get better with each successive week of the pregnancy.

Week 29:  During this week of your pregnancy, which is approximately 27 weeks after conception, the baby’s skeletal system is fully developed, however, the bones themselves are still quite pliable and soft.  This stage of the pregnancy marks the time when the baby will start to create stores of minerals, such as iron, phosphorus, and calcium.

Week 30:  During this week of your pregnancy, which is approximately 28 weeks after conception, the baby may have a full head of hair, and the eyes are wide open.  Your baby may be more than 10 ½ inches (270 millimeters) long from crown to rump and weigh nearly 3 pounds at this stage of the pregnancy.

Week 31:  During this week of your pregnancy, which is approximately 29 weeks after conception, the sexual development of the baby is continuing to progress.  If your baby is female, her clitoris is quite prominent, and if your baby is male, his testicles are traveling into the scrotum through the groin.  

Week 32:  During this week of your pregnancy, which is approximately 30 weeks after conception, the baby is starting to practice breathing, even though the lungs are not quite fully developed.  The baby’s body is starting to absorb vital minerals, such as calcium and iron, and toenails have become visible on its little feet.  The lanugo, which is the layer of soft thin hair that has been covering the baby’s body for several months, has started to fall off by this stage of the pregnancy.   You may begin to notice that the force behind the pokes and kicks that you have been feeling thus far are starting to become stronger.  Your baby may be more than 11 inches (280 millimeters) long from crown to rump and weigh nearly 3 ¾ pounds at this stage of the pregnancy.

Week 33:  During this week of your pregnancy, which is approximately 31 weeks after conception, the pupils of the baby’s eyes have developed to the point that they can dilate and constrict, effectively detecting light that enters the eyes.

Week 34:  During this week of your pregnancy, which is approximately 32 weeks after conception, the fingernails of the baby’s small hands has reached the tips of the fingers.  Your baby may be approximately 12 inches (300 millimeters) long from crown to rump and weigh nearly 4 ½ pounds at this stage of the pregnancy.

Week 35:  During this week of your pregnancy, which is approximately 33 weeks after conception, the vernix caseosa, which is the white coating that protects the skin of the baby, has started to thicken.  The overall shape of the baby’s body is becoming noticeably rounder.

Week 36:  During this week of your pregnancy, which is approximately 34 weeks after conception, the rate at which the baby is gaining weight has started to increase.  The baby will gain approximately ½ pound (227 grams) per week for the remaining weeks of your pregnancy.  The growing size of the baby may tend to limit the pokes and kicks that you were feeling prior to now, however, stretching, wiggling, and rolling may become noticeable.  You may want to try to pay attention to the activity levels of the baby at this stage of your pregnancy.  Discuss the expected hourly activity level of your baby with your health care provider, and feel free to contact them should you start to notice a decrease in the level that is anticipated.

Week 37:  During this week of your pregnancy, which is approximately 35 weeks after conception, you have reached the point where your baby will be considered full term.  The baby’s internal organs are fully developed, and they can be expected to function properly on their own.  In preparation for the upcoming birth, the baby may start to shift into a position where the head is pointed downward.

Week 38:  During this week of your pregnancy, which is approximately 36 weeks after conception, your baby’s toenails have reached the tips of the toes, and he or she is developing a firm grasp.  With the passing of each day, the nervous system and the brain of the baby are functioning more efficiently, and this process of development will continue through childhood and adolescence.  Your baby may be approximately 13 ½ inches (340 millimeters) long from crown to rump and weigh nearly 6 ½ pounds at this stage of the pregnancy.

Week 39:  During this week of your pregnancy, which is approximately 37 weeks after conception, the chest of the baby is starting to become more prominent.  In regards to sexual development, for the girls, the labia majora is well developed, and for boys, the testicles are continuing their decent into the scrotum.  The fat layer located below the skin has developed to the point where it can maintain body temperature with just a slight level of assistance from mom.  The baby has been receiving a continual level of antibodies from the placenta, which will serve to offer protection from infections during the first six months of life.  Should you choose to nurse your baby, the milk that you produce will provide even more antibodies.

Week 40:  During this week of your pregnancy you have reached your due date, which is approximately 38 weeks after conception.  Your baby may be approximately 14 inches (360 millimeters) long from crown to rump and weigh nearly 7 ½ pounds.  Please keep in mind, however, that this is an approximation, and that completely healthy babies come in all sizes!  You should not be alarmed if the specific due date has arrived and passed with no signs of active labor.  It is completely normal for a baby to be born a week or two late!  It is also just as normal for a baby to be born early.  Lastly, congratulations!




Related Categories

  • Pregnancy



  • Get Access to Support, Benefits, and Resources for Expecting Parents. Join the EPAOA Community for FREE!




    Comments


    Trending News & Information











    The smart way to shop for your baby's needs
    > Diaper Coupons
    Baby Wipes Coupons
    > Baby Proof House
    > Baby Crib Sets
    > Baby Food Coupons
    > Parenting Magazines
    your baby's needs