The total period of pregnancy is approximately 40 weeks. These 40 weeks are counted from the first day of your last menstruation. However, till the due date, the baby has completed only 38 weeks. This is because, the egg does not fertilize for the first two weeks. Most of the babies are born between the 38th and the 42nd week. Pregnancy is divided into trimesters. The first trimester is from week 1 to week 12. The second trimester is from week 13 to week 26, and the last trimester is from week 27 till the birth of the baby. According to the week by week calendar that is given here, it would start from the third week. This calendar provides information about the development of the baby, changes in one's body, and nutritional requirements. It also includes the possible complications that could be experienced at that time. Week-By-Week Development The following is a weekly pregnancy calendar that shows fetal development: Week 1 and 2 In the first two weeks, one is not actually pregnant and the baby is not conceived. Since, the expected delivery date is calculated from the first day of one's last menstrual period, thus, in these two weeks you have time to prepare your body for the baby. In the second week, you will be in the middle of the menstrual cycle and the ovulation will take place. This is the time when you are most likely to conceive. Week 3 The baby starts developing from this week. However, the feeling of pregnancy would still not be there. The baby's sex is determined at the fertilization level itself. Supplements like folic acid are advisable during this period. Nourishing your baby with required proteins, calcium, and iron is necessary. Many a time the folic acid supplement is recommended when one tries to conceive the baby. Folic acid is responsible for the development of the spinal cord and the brain of your baby. Calcium is necessary for the growth and development of bones. Week 4 In the fourth week, the baby is two weeks old and the fetal development is still in its early stages. The signs of being pregnant still may not be observed. Week 5 In the fifth week, development of the baby's heart, bones, muscles, and central nervous system would take place. Further, the facial features of the baby would start developing in this month and end in week 9. The early signs of pregnancy such as nausea, fatigue, tender breasts, and frequent urination, are likely to appear in this month. Week 6 Nutrition is an important aspect at this stage and also, in the overall process of pregnancy. In this week, the heart of the baby would start beating, and the development of eyes starts taking place. One should ensure that adequate amounts of omega-3 fatty acids and folic acids are consumed. Strictly stop smoking after this stage because it would affect the baby to a great extent. The intake of caffeine also must be reduced. It is advisable to take proper care of oneself at this stage, in order to avoid early pregnancy miscarriage. The nutrition plays an important role in this week as the development of the baby is at its peak. At this stage, one should consult the obstetrician and discuss their medical history. Week 7 The legs and arms of the baby start developing in this week. The heart is divided into left and right chambers. The internal organs like appendix, pancreas, and intestine start developing. In this week, one would experience a slight gain in weight. The intake of calcium is a must in this week, as it will help prevent any complications that could occur at this stage. For calcium, dairy products like cottage cheese, milk, custard, and yogurt must be consumed. Week 8 In the 8th week, the baby will have eyelids, retina, nose tips, and even the ears would start developing. The arms of the baby would be slightly curved over the heart. Further, the cerebellum, a part of the human brain, would start developing. At this stage, the gonads start developing in the baby. Pain, vaginal bleeding and cramps would be experienced. Week 9 In the 9th week, the arms of the baby grow longer and the fingers are developed. However, the fingers are still developing in this week. Legs, toes, ears, eyes, and neck are the other parts of the body that are growing in this week. As the baby grows, the mother's waist line would start getting bigger. The baby's growth and development is dependent on the weight gain that one would undergo. Keeping a check on one's weight regularly, at the time of regular visit to the obstetrician is important. The intake of Vitamin C is important during this phase, as it reduces the chances of premature birth. Week 10 At the end of this week, the embryonic period comes to an end, and the fetal period begins. The baby's head will appear more rounded and the hair follicles, fingernails, and toenails will start developing in this week. At this stage, one must start putting on weight. If that is not the case, consult the obstetrician immediately. Week 11 In this week, the baby's iris, as well as the shape of the brain gets developed. The development of gallbladder, pancreas, and thyroid gland would be almost completed. In this week, the body would undergo most of the changes that one experiences throughout the pregnancy. Carbohydrates should form a major part of the mother's nutrition at this stage. Week 12 In the 12th week, during the Doppler scan, one would hear the heartbeats of the baby. The fingers of the baby are now separated. The external sex organs of the baby would now show up, which indicate whether the baby is a female or a male. In this week, the early symptoms would start disappearing, and the uterus becomes very big and one may feel it above the pelvic bone. Avoid wearing tight fitting clothes. Even high altitude flights should be avoided. Week 13 The facial features become more prominent, and the eyes and ears start coming closer. The growth of your baby will strikingly slow down in this week. At this stage, the external genitalia are distinguishable and you can determine the sex of your baby. It is in this week itself, that your baby will pass the first urine into the amniotic fluid. At this stage, the mother-to-be would need maternity clothes due to the expanding waistline. Many women may experience an infection in the gallbladder and it is recommended that one should consult the obstetrician instead of opting for over-the-counter medicines. One's breast size changes and the areola would become darker during this phase. Week 14 The hands of the baby start becoming functional and the baby starts using its fingers and thumbs. The sucking muscles of the baby develop in this week and the mouth of the baby undergoes a lot of changes. At the end of this week, breathing, sucking, and swallowing are the movements that are developed. In this week, the mother must rest for at least 1 hour, with her feet in an elevated position. Drink lots of fluids and eat adequate amount of fiber. Many women are affected by constipation during this week. Week 15 In this week, the skin of the baby is thin and covered with hair called lanugo. The bones of your baby would be developing everyday, and would become harder and harder. The baby would now swallow and digest the food, and pass the waste through the system. At this stage, one must follow a regime of sleeping and waking up at the same time every day. Also, regular exercises must be done. One must sleep in a comfortable position from this week and the bedroom must have a temperature of about 21 degrees. Week 16 In this week, many women experience that their baby is moving. The muscles of the head and neck of the baby are becoming stronger. The body of the baby grows faster in this week, as compared to the previous week. Nasal congestion, headaches, and allergies are experienced by many pregnant women. Week 17 The baby is likely to gain weight in the seventeenth week, and the mother would experience fatigue. Features become more defined. Exercising moderately is recommended in this week. Many women prefer to eat vegetarian food, as meat can be nauseating to them. One must consult a nutritionist about the food that should be consumed at this stage. Week 18 In this week, the baby's fingers and toes will develop swirls and creases. The early fecal waste matter is developed in the baby and is accumulated in the bowels of the baby. This fecal waste is called meconium. Meconium consists of amniotic fluid, digestive secretions, and cell loss of the baby. The eyes and ears of the baby would be placed in the proper position. At this stage, one's heart will have to work 40% more than the normal conditions to pump more blood. Whitish vaginal discharge is commonly experienced during the pregnancy, and is considered normal. One must keep a check on the weight, and the weight gain must be as steady as possible. Exercises and a healthy diet must be strictly followed for a normal pregnancy. In the last two trimesters, the carbohydrate intake must be increased. Week 19 Vernix caseosa is a white fluid that is developed to form a protective layer on the baby's body. This fluid is beneficial for the development of glands and sensory organs. The primitive eggs in the ovaries are already developed at this stage, if one has a baby girl. Fat deposits are developed around the neck and chest. Eyebrows and scalp hair are developed in this week. Routine blood pressure check is recommended as many pregnant women experience dizziness due to hypotension. Week 20 The uterus is now grown and comes in line with the belly button. Skin starts growing on the body of the baby. The slimy vernix is still there on the body of the baby which helps to protect it from the amniotic fluid. The baby's movements are more pronounced this week. The arms and legs of the baby become stronger and hence, the baby kicks would also become stronger. Week 21 The baby's heart would start beating faster in this week and the legs of the baby would have now grown in their final proportion. Food cravings are common in many pregnant women. Fruit juices and other fluids must be consumed by the pregnant women. Week 22 A rapid development in the brain is observed in the baby. External sounds can wake up the baby from sleep. In a baby girl, the ovaries are developed in this week and in the boy, the scrotum. Dizziness is observed in many pregnant women. However, if frequent dizziness is experienced, consult the obstetrician at the earliest. Lastly, one should not forget to increase the fluid intake in the diet. Drinking lots of water can help avoid the headache and bladder infection. Week 23 The baby's ears are developed and become stiff. The hair on the baby (lanugo) become darker. The baby will gain almost double the weight (as compared to this week's weight) in the coming weeks. The pancreas of the baby would start developing and secrete insulin so that the baby can now break down sugar. In this stage, the mother-to-be may experience pain in ligaments and sciatic nerve. In the second and the third trimester, the intake of proteins must be increased in your diet. Week 24 Frequent nosebleeds are experienced by many people. A lot of hormonal changes are observed and the body starts adapting to the pregnancy. Calcium is very important as it helps to develop the bones, teeth, heart, and nerves of the baby. Many doctors recommend to have calcium supplements during this trimester. Week 25 The blood vessels start developing under the skin and these blood vessels are filled with blood. Swelling and bloating are symptoms that are observed during this phase. Vitamins and minerals that are essential for the baby's growth are supplied by the supplements that are recommended by the obstetrician. Also, bladder infections are very common in this period. Week 26 The baby develops a sleeping pattern by this week. Many a time, the baby may get affected by arrhythmia, in which the baby misses a few heartbeats here and there. The reason for this is that the baby's heart is developing at this stage. This arrhythmia will disappear after a certain stage. The uterus will start growing bigger and bigger and will cause leg cramps, back pain, and pelvic pressure. It is recommended to eat fish at this stage because fish have the omega-3 essential fatty acids. This is the end of your second trimester. Week 27 In the 27th week, the baby will develop the sense of sight. The connection of the baby's eyes and brain is formed in this week. Some women may develop gestational diabetes. Protein must be included in the diet of a pregnant woman along with nuts and dairy products. Week 28 The baby will appear to be chubbier in the ultrasound due to the development of fat deposits. The muscle tone of the baby will start improving in this week. In pregnant women, emotional changes may be experienced at this stage. Hormonal changes are responsible for these emotional changes and mood swings. Fresh fruits and vegetables must be included in daily diet. Fatty foods and sugar must be consumed in moderation. Week 29 The baby's lungs and brain get developed in this week. The baby will gain weight rapidly and would be able to breathe on its own. The intake of smaller, frequent meals would prove helpful. Drinking lots of water and eating dried fruits and raisins is preferred in this week. Week 30 Myelin is a fatty substance that covers nerve cells of your baby and improves the efficiency of nerve messages of the baby's brain. A transparent vaginal discharge in women is common throughout the period. It is recommended to consult a doctor if the discharge is thin or white, yellow, red or green and is foul-smelling and if it causes a burning sensation. Week 31 In this week, the uterus grows to its fullest size, giving rise to pain in the pelvic area. The ribs will also experience the pressure. This is the reason of frequent backache in the third trimester of this period. Exercise regularly and maintain a sleep pattern. It is advisable not to drink lots of fluids at night, as you may need to keep going to the toilet all night. Week 32 By this week, the baby has developed all five senses. The mother is likely to experience severe back pain in this week. It is recommended that you must have proper prenatal care during this period. Keep the hospital bag ready as there are chances that anything can happen in the coming weeks. Week 33 One may have severe back pain and sciatic nerve pain. Often, one may feel uncomfortable while sitting. The color of the baby's skin turns pink from red, and fat gets deposited under the skin. The baby continues to gain weight in this week. Week 34 The immune system of the baby is developed in this week. This helps the baby fight against diseases and infections. In this week, the baby's head enters the birth canal. Pressure is experienced in the pelvic area. However, more room is created in the stomach and one is able to breathe easily than before. Week 35 Fat gets deposited on the baby, and the baby's arms and legs become fatter. In this week, one has to gather information like the blood group, the due date, details of last pregnancy (if any), the doctor's contact number, and the husband's number. Week 36 In this week, it is common for some women to lose weight as all the food that they consume is converted to energy. If in the earlier week, the baby has not fallen in the birth canal, in this week it will fall in the birth canal with its head down. However, sometimes, the baby does not fall in the birth canal. At such times, a C-section operation is performed by the doctors during the baby's birth. Week 37 Earlier in this week, the baby would have grown rapidly. However, during the last days of this week, the growth of the baby will slow down. Be prepared, as the signs of labor might appear soon. Week 38 In this week, the baby gathers a lot of meconium in his/her body. This will pass from the body as the first stool. The would-be-mother may experience tiredness and bloating. She may not feel like eating in this week, but should eat properly to fulfill the daily nutritional intake. Week 39 In this week, one must concentrate on the nutrition, as after the childbirth, one will be breastfeeding the baby. On an average, one must take 500 calories extra everyday. Vegetables, fruits, rice, pasta, and dairy products are recommended during this week. Week 40 This week would be marked by the onset of labor, with mother-to-be experiencing contractions. Initially, when the contractions start, continue deep breathing. Women who have crossed the 40th week with no signs of labor must not worry. The delivery can take place anytime till the 42nd week. The health of the woman and her baby is very important during the entire development process. So, eat healthy and exercise, so that you can welcome your bundle-of-joy. Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.