From Conception to Birth – Your 42 Week Pregnancy Calendar

Congratulations – you are going to have a baby.  Your life is about to change in many wonderful ways, and your body will be undergoing many changes over the next weeks and months.  As a mom to be it is important for you to know what to expect when you are expecting, and this pregnancy calendar is designed to do just that.

Week 1

It may seem odd, but week one actually starts with your monthly menstrual period.  That is because your due date is calculated based on the first day of your last period.  At this point your baby has not yet been conceived, but there are some steps you can take to keep yourself – and your future son or daughter – healthy.

That’s because your health and the health of your baby go hand in hand.  If you are actively trying to get pregnant it is important to avoid things that could harm the development of your baby.  Avoiding alcohol and other drugs is essential at this point – the presence of alcohol or drugs in your system at the time of conception could have a profound effect on the developing fetus.

It is also important to talk to your doctor about any medications you are taking, including over the counter medications and even herbal remedies.  Even seemingly innocuous medications could have an effect on your baby, or on your ability to conceive, so it is important to let your doctor know you plan to get pregnant.

Week 2

Fertilization will take place this week, and by the end of the week you will be officially pregnant.  Even though you will not know your baby’s sex for many more weeks, the gender of your baby will be determined the moment the egg and sperm meet. 

Even before your baby is conceived, your body will be getting ready to host its new resident.  The uterine lining that will serve as nourishment for the growing baby is beginning to develop.  Your body will also secrete a follicle stimulating hormone designed to help the egg mature.  When the egg is mature ovulation will take place, and at this point you will be the most fertile.  If you are trying to have a baby, now would be the perfect time for a romantic dinner followed by a night of passionate lovemaking.

Week 3

At this point you most likely do not realize you are pregnant, but in fact a new life has begun to grow inside you.  Your baby has just been conceived, but he or she is getting off to a great start.  At this point the fertilized egg has begun to divide exponentially, turning one cell into two, then four, then eight and so on.  The cell division will continue as the fertilized egg travels down the fallopian tubes into the uterus.  By the time the fertilized egg has reached the uterus the clump of cells resembles a tiny ball.

This ball of cells will become hollow and filled with fluid, at which point it is known as a blastocyst.  By the end of week three the blastocyst will become attached to the lining of the uterus in a process known as implantation.  The lining of the uterus will provide vital nutrients to the fetus as it grows and develops.

During this time it is important for moms to be to get plenty of good nutrition, particularly nutrients like folic acid.  Folic acid is particularly important for the growing fetus, playing a role in the prevention of many common birth defects.  Since you probably don’t yet know you are pregnant, it is important to eat right at all times, both for your own health and that of your future son or daughter.

It is also a good idea to increate the amount of protein in your diet when you are trying to conceive.  This added protein will play a big role in the development of your baby.  Extra calcium is important as well, both for your own bone health and the development of your fetus.  Be sure to eat lots of quality dairy products, dark green vegetables and other calcium rich foods.

 Week 4

At four weeks your baby has morphed from a blastocyst into an embryo.  The embryo is made up of two distinct layers of cells and these cells will eventually develop into all of your baby’s organs.  At this point in development the yolk sac and amnion will develop as well.  The amnion will be filled with amniotic fluid, which will surround that embryo and protect it.  The yolk sac produces the blood needed to nourish the embryo at this point.  Later in the pregnancy this vital role will be taken over by the placenta.

During this stage of development the embryo will be burying itself deep into the walls of the uterus.  Once the embryo is fully implanted it will start to produce a hormone known as human chorionic gonadotropic, or hCG.  This hormone will serve to maintain the lining of the uterus, and it will also signal the ovaries to stop releasing eggs.  This is why your period stops after you have conceived.

During this period some women may feel some slight cramping and a bit of spotting, and sometimes this spotting is mistaken for the monthly menstrual cycle.  If you are unsure about your pregnancy status it is a good idea to take a pregnancy test.  Home pregnancy tests look for the presence of the hCG hormone, so you should be able to get an accurate result at this time.  If the results of the home pregnancy test are unclear it is a good idea to make an appointment with your gynecologist.

Week 5

At week five the embryo that had been an indistinct clump of cells has begun to take on a definitive shape.  By week five the embryo will have developed the neural tube that will eventually become the baby’s brain and spinal cord.  The embryo will also have a distinct bulge in the middle where the heart will eventually form.  It is also during this time that the placenta will develop and take over the job of nourishing the baby.

It is also at this point that moms to be may feel the first signs of nausea and morning sickness.  Some women are greatly troubled by these symptoms, while others may see virtually nothing.  Nevertheless it is a good idea to avoid foods that often trigger morning sickness.  These problem foods include soft cheeses like blue and brie, juice, hot dogs, deli meats, raw shellfish and raw eggs.

Now is also the time to pass the job of cleaning the litter box on to your partner.  Cat feces can carry a disease known as toxoplasmosis, which can be very dangerous to the developing fetus.

Week 6

By the sixth week the embryo’s brain and nervous system are starting to develop in earnest.  At the same time the precursors of the eyes, known as optic vesicles, are starting to develop on the sides of the head.

At this point the baby’s heart will start to beat, and you may even be able to pick up this heartbeat during your ultrasound exam.  The precursors of the respiratory system and digestive system are also forming at this time, as are the small buds that will develop into the baby’s arms and legs.  At this point your baby is still quite small, probably about 2 to 5 millimeters in length.

By week six many moms to be may be seeing some of the more unpleasant signs of pregnancy, including fatigue and nausea.  Although most of us are familiar with the term morning sickness, this sudden nausea can appear at any time, so be prepared. 

You may also find that your breasts have become quite tender, and you may find yourself urinating more than normal due to hormonal changes that can affect your kidneys.  If you find yourself feeling unwell and run down just think about your baby and the joy he or she will bring to your life.

Week 7

At this point your baby is adapting well to its life inside your body.  By this time your baby’s umbilical cord has already formed, and this cord will serve as a lifeline to you throughout the pregnancy.  The umbilical cord will provide vital oxygen and nourishment for the fetus throughout the pregnancy and help to dispose of any waste products. 

Your baby’s face will also be forming at this point, as the mouth, eyes, ears and nose become more defined and recognizable.  The baby’s digestive system and lungs are also continuing to form as week seven rolls around.

During the seventh week of pregnancy you will have developed a mucous plug at the opening of your cervical canal.  This plug forms as a part of pregnancy, and its job is to seal off and protect the uterus and its precious cargo.  This plug will eventually be lost as the cervix dilates in preparation for the delivery of the baby, but that is still a long way off.

Week 8

By the eighth week of pregnancy the baby’s fingers and toes have just begun to form.  At this point your baby is able to flex his or her arms at the elbow and the wrist.  The digestive tract is continuing to grow as well, with longer intestines and a more pronounced abdomen.  The eyes are continuing to develop as well, and they have even started to develop a bit of pigment.

At this point the buds that will become the baby’s genitals are even becoming apparent, although these features will not be distinct enough to accurately determine if you should paint the nursery pink or blue.

During this period you will continue to experience the symptoms of pregnancy, including extreme tiredness, nausea and swelling of your abdomen.  Now is also the time to schedule your first prenatal exam.  As soon as your pregnancy is confirmed it is important to have a thorough exam and pay careful attention to the advice of your doctor.  Proper prenatal care is particularly crucial during the early weeks of your pregnancy.

Week 9

At this point your baby still has a tail, but that tail has begun to shrink and will eventually disappear altogether.  The baby’s head continues to grow, and it will appear quite large for the body.  By this week your baby will be between 16 and 18 millimeters in length, and you will be able to see the flaps of skin that will develop into his or her eyelids.

Your baby’s digestive system is continuing to develop as well, and the intestines are continuing to get longer.   The anus has now formed as well, as have the reproductive organs, including the testes or ovaries.  Your baby may begin to move at this point, so be on the lookout for these exciting signs of life. 

Now is the time to start researching your family medical history, paying careful attention to any genetic problems or hereditary diseases.  Be prepared to discuss your family history with your doctor at your first prenatal exam.  Also discuss any medications you are taking, including not only prescription medications but herbal remedies and over the counter preparations as well.

Week 10

By the tenth week of development all of your baby’s vital organs have formed and they are all beginning to work together.  Other changes, like the separation of the fingers and toes, will have taken place as well.  At this point your baby’s vestigial tail will have disappeared completely, and tooth buds will be forming in his or her mouth.  If the baby is a boy his testes will have already begun to make testosterone, so be prepared. 

The tenth week of pregnancy also marks the end of the embryonic period.  By this time the baby is now fully recognizable as a human being, and beginning with week 11 he or she will officially be called a fetus.

During this week you may be having a prenatal visit, complete with a full battery of tests.  You will probably have your blood checked and your blood pressure evaluated during your exam, and you may also have an external abdominal exam to determine the size of the baby and his or her position in your uterus.  You may also be asked for a urine sample so that other important tests can be done.  If you have a genetic predisposition to certain diseases or a family history of congenital conditions you may be asked to undergo further testing.

Week 11

As week 11 arrives your baby will have started to grow quite rapidly, and by now he or she is about two inches long.  At the same time the blood vessels in your placenta are expanding to accommodate the growing fetus.  The placenta is also increasing the number of blood vessels in order to provide more nourishment as the baby continues to grow.

The development of your baby’s face is continuing as well, and by now most facial features are easily recognizable.  At the same time the baby’s head continues to be disproportionately large for its body, making up about half of the total length of the body.

Your baby’s reproductive organs are growing rapidly as well, but it will still be difficult to determine the gender.  At this stage of gestation the external genitals on male and female fetuses can look quite similar, so don’t start painting the nursery just yet.

By this stage of your pregnancy you will probably have put on some weight, since your baby will need extra nutrients to continue his or her growth.  In most cases a good guideline for weight gain is between 25 and 35 pounds over the course of your pregnancy, but it is important to talk with your doctor about what you can expect in terms of your weight.

Week 12

At twelve weeks of gestation your baby’s brain will be undergoing a period of rapid growth, ready to fill that big head.  Your baby will also begin to sprout fingernails and toenails at this point.

As the end of the first trimester approaches your baby will have functional kidneys, allowing the fetus to pass urine.  The umbilical cord will remove these waste products while providing much needed oxygen to help your baby continue his or her development.

It is at this point that many moms to be will develop that distinctive glowing appearance.  While some of this glow is due to the excitement of impending motherhood, it can also be a result of increased blood flow and extra hormones.  Unfortunately these hormonal changes can also cause acne in some women.  While it may be unpleasant it is important to treat this pregnancy-related acne with care.  Before using any treatment it is important to check with your doctor, since some acne treatments can be harmful to your baby’s development.

Week 13

As the second trimester gets underway the placenta will have developed fully and it is now providing the baby with nutrients, oxygen and a well developed waste disposal system.  The placenta will also be pumping out hormones like progesterone and estrogen - hormones that will help to maintain the pregnancy.  At this point your baby has eyelids in place to protect the eyes, and at this stage many babies will begin to such their thumbs.

You have probably been taking prenatal vitamins on the recommendation of your doctor, and hopefully you have been eating a healthy and balanced diet.  All of these extra nutrients are serving your baby well, helping in the growth and development of the young fetus.  It is important to keep going to your prenatal appointments and to keep following the recommendations of your doctor.

Week 14

By the fourteenth week of development your baby may have some hairs on the face or body.  As growth continues these fine hairs, known as lanugo, will come to cover most of the baby’s body surface.  This protective coating will be shed just before your baby is born.

Your baby now has fully formed genitals, so at this point you will be able to determine whether you will be having a son or a daughter.  Some parents are just dying to know which color to paint the nursery, while others prefer to wait for the big surprise.  This is an important decision, and one only you and your partner can make.

If you are over the age of 35 your doctor may talk to you about amniocentesis.  This procedure is typically performed between 15 and 18 weeks of gestation, and it is able to pick up many genetic abnormalities.  The odds of many birth defects increase with the age of the mother, so if you are having a baby later in life you may want to consider this procedure.  Amniocentesis does carry a slight risk of miscarriage, so it is essential to weigh these risks against the potential benefits.

Week 15

At this stage of gestation your baby’s skin is continuing to grow, providing important protection to those delicate internal organs and structures.  Your baby will also be growing additional hair, including eyebrows.  Facial features continue to form as well, and at this stage your baby’s ears are nearly in place, although they are still a bit lower than they will be on the newborn.

The skeletal system is continuing to grow as well, as are the muscles that will power that tiny skeleton.  At this point your baby is probably moving around a great deal, and you may even be able to feel some of those movements.

By now you will probably be ready to trade in those traditional clothes for looser fitting maternity wear, as your stomach will have greatly increased in size.  As your abdomen continues to swell it is important to wear clothes that are comfortable and loose fitting.

By this point you may also find that those pregnancy hormones have kicked into high gear.  You may find that you are on an emotional roller coaster from time to time, up one minute and down the next.  Try to take it all in stride, content in the knowledge that you will be meeting your new son or daughter very soon.

Week 16

By now your baby weighs approximately four ounces and measures nearly five inches in length.  At this stage of development your baby can hold his or her head up, and the facial muscles are developed to the point where common expressions may be visible.  Your baby can squint, frown and maybe even smile.

At this point in your pregnancy you may be offered a blood screening test called a “triple screen” or “triple marker” test.  This specialized maternal blood test is designed to measure the levels of a protein in the baby’s blood, along with two hormones in the blood of the mother.  These test results can provide an indication that the baby is at risk for common birth defects like spina bifida or Down syndrome.  Chances are your baby will pass these tests with flying colors, but it is a good idea to talk to your doctor about the value of this screening.

Week 17

By now your baby is over five inches long and nearly five ounces in weight.  Even after all these weeks of development your baby is still quite small, but he or she will be growing a great deal over the coming weeks and months.

By now the placenta that provides such important nourishment is growing larger to accommodate your growing baby.  This vital source of nutrients contains literally thousands of blood vessels which bring nutrients to the growing fetus.

At this point in your pregnancy you may be noticing a distinct swelling in your breasts as the pregnancy hormones coursing through your body prepare for milk production.  These changes can increase the size of your breasts, so you may find yourself shopping for a new bra.

Week 18

At 18 weeks of gestation your baby’s ears will have moved to their final position on the head, and the ears will now stand out from the head instead of lying flat.  In fact your baby can probably hear sounds at this point, so why not sing your son or daughter a lovely lullaby?

Your baby’s eyes are continuing to develop as well, and those eyes are now facing forwards instead of being stuck off to the sides.  In fact those eyes may be sensitive enough to detect the light of a flashlight placed against your growing belly.  At this point in the development your baby’s bones will have begun to harden.  The bones in the legs are among the first to harden, but the others will soon follow suit.

At this point you are probably starting to prepare for the arrival of your new baby.  You may have started to work on the nursery, and you may already be shopping for baby clothes, a crib and other essentials.  While you prepare for your new son or daughter it is a good idea to also start shopping for a good pediatrician.  It is a good idea to get some recommendations from family members, friends and other health care providers, and to schedule visits with several doctors before making a final decision.

Week 19

As the nineteenth week of development rolls around your baby will have developed a strange protective coating.  Known as vernix caseosa, this waxy white substance will cover the entire skin surface, serving as a protective layer and preventing the delicate skin from becoming scratched, chapped or otherwise damaged.  Were your baby to be born at this point you would see this covering, and this is why premature babies appear to be covered with such a coating at birth.

Your baby will also start to develop so-called brown fat at this point.  Different from traditional white fat, this special substance will help to keep the baby warm after it is born.  As the pregnancy progresses your baby will continue to add more layers of fat to provide both protection and warmth.

At this point you may begin feeling your baby move in earnest.  While you may have felt some subtle movements before, at this stage you will definitely know you are pregnant.  The first movements you feel may be very small, but these movements will quickly progress to kicks and other indistinguishable movements.

Week 20

At this point you are now roughly halfway through your journey from conception to birth.  By this time your baby has grown considerably and now weighs about 11 ounces and is more than six inches in length.  The baby is taking up more and more of the space available in your uterus, and this increased size can put pressure on your stomach, your lungs, your kidneys and of course your bladder.  You may feel like you are chained to the bathroom as your growing baby continues to push on your kidneys and bladder.

It is at this point that an ultrasound exam can be of great value, so if you haven’t had one already be sure to talk to your doctor.  An ultrasound can tell your doctor a great deal about your growing baby, including size, position and of course gender.  During the ultrasound the doctor will also examine the placenta, the amniotic fluid and the umbilical cord. 

Week 21

By this time the amniotic fluid will have an additional purpose. Up until now its only purpose was to cushion and protect your baby, but now the baby may be able to absorb some sugar from the amniotic fluid as well.  Even so, most of your growing baby’s nutrition will still be passed from your body to hers via the placenta.

At this point in development your baby’s bone marrow has developed to the point where it is able to form blood cells, and this bone marrow will be the major source of blood cell production going forward. 

By this point in your pregnancy you may have developed some excess weight gain, and you may be wondering if it is safe to exercise.  Mild exercise can help reduce some of the more troublesome aspects of pregnancy, such as varicose veins and frequent backaches, but it is important to take things slow and easy.  You will get plenty of exercise once you start chasing your toddler around the house.

Week 22

By this point your baby’s senses will be developing very rapidly, and there is growing evidence that babies at this stage of development have a good sense of the limited world around them.  By this time your baby will have developed taste buds on the tongue, and the nerve endings are developed enough to experience tough.  Your baby may start touching his or her face at this point, and thumb sucking may become more frequent.

By this point in your pregnancy you may start to experience some painless contractions as you uterus starts practicing for delivery.  These harmless contractions are known as Braxton Hicks contractions, and they are nothing to worry about.  If on the other hand you experience painful contractions it is important to consult with your doctor.

Week 23

At this point in gestation your baby is starting to develop more of the protective fat that will keep him safe and warm after delivery.  The skin on your baby will still have a wrinkled and loose appearance, but it will soon tighten up and become smoother. 

Your baby is probably starting to move around a bit more by this point, moving the muscles in the arms and legs and generally getting a great little workout.  You will probably be able to feel the effects of these daily workouts in the form of kicks, punches and other movements.  By this time your baby will probably weigh about a pound.

As your delivery date gets closer you may find you have more trouble sleeping, as both emotional and physical signs of pregnancy take their toll.  You may find that you have some pregnancy-related anxiety, especially if this is your first baby. You may also find yourself getting up several times a night to urinate as your growing baby continues to place pressure on your bladder.  Other unpleasant signs of pregnancy may manifest themselves at this point as well, including leg cramps, backaches and heartburn.

Week 24

By 24 weeks of development your baby has started to develop more functional lungs.  While your baby is still receiving oxygen through the placenta, he or she is getting ready for that all important first breath. 

By this time your baby’s inner ear structures are now fully developed, so your baby may be able to tell when he is right side up or upside down.  It is these inner ear structures that give us our sense of balance, so by now your baby may have a sense of where he is in space.

At this point in your pregnancy your doctor may order a very important test.  Known as a glucose screening, this test will check for the presence of gestational diabetes.  This temporary form of diabetes can cause serious health problems if left undetected, so be sure to ask your doctor about this important screening.

Week 25

By week 25 you may notice that your baby seems to be experiencing sleep and wake patterns.  There may be times when your baby is completely still, and also times when he or she is quite active.  At this point your baby may have the ability to hear your voice, so it is a good idea to talk to your future son or daughter regularly.  Many moms to be also like to play soft classical music, and some babies may react positively to this gentle stimulation.

Some moms to be may experience unpleasant digestive symptoms like heartburn and acid reflux, due to the changes taking place in the body during this stage of pregnancy.  It is important to talk to your doctor before treating these unpleasant side effects of pregnancy, as some common over the counter medications could harm your growing baby.

Week 26

At this point your baby’s eyes will soon start to open and blink.  Up until now those little eyes have been sealed shut, but they will soon open up and provide your baby with a fresh new perspective on the world.   At this stage of development your baby will weigh somewhere around two pounds, and he or she will continue to grow steadily form now until birth.

Now would be a good time to start baby-proofing your home, covering up those electrical outlets, power cords and other potential sources of danger.  It is also important to go through the home and remove any potential choking hazards, install a baby gate at the doors and stairs and look for any other sources of danger.

Week 27

By week 27 your baby will have an appearance similar to its appearance at birth.  By now the lungs, the liver and the immune system will be well on their way to becoming mature, but all of these systems still have a ways to go.

Your baby’s hearing is continuing to develop, and he or she may even start to recognize your voice and that of your partner.  Keep in mind, though that the sounds that reach your baby will be somewhat muffled by the amniotic fluid and by the thin coating that protects the skin of babies at this point in their development. 

At this point in your pregnancy you may want to sign up for a child rearing and childbirth course.  Your local community center or hospital probably has such courses available, so be sure to take advantage of the opportunity.  After all, no one is born knowing how to be a good mother.  Child rearing is definitely a learned skill.  You should also consider signing up for a course in infant first aid and infant CPR so you will be prepared for any unforeseen emergencies that may arise.

Week 28

By now your baby weighs a little bit over two pounds, and measures some 10 inches in length.  At your next prenatal appointment your doctor may check to see if your baby is in a normal position or a so-called breech position.  If your baby is in a breech position he or she may need to be delivered using a C-section.  Even if a breech position is found, keep in mind that your new son or daughter still has two months in which to change positions.

At this point in your pregnancy your doctor may also take some blood tests to measure the Rh factor in your blood.  If you lack this Rh factor, or if you are Rh negative while your baby is positive, there could be health problems like anemia or jaundice when your baby is born.  Your doctor can prevent these potential problems with a simple vaccine -  known as Rh immune globulin.