First Trimester Fetal Development (Week by Week)
First Trimester Fetal Development and maternal symptoms week by week
First 2 weeks
As I explained in the first article, the first two weeks that we count towards the 40 weeks of pregnancy, you are not really pregnant. Health care providers calculate gestational age by counting from the first day of the last menstrual period to 40 weeks, but conception happens on average 14 days after the first day of the last menstrual period. In other words, the egg gets fertilized by the sperm around day 14
Week 3
After conception cells DNA mix, then cell division begins. One cell splits into two, two into four, four into eight and division continues. Within seven days of conception, the pregnancy is implanting into the uterus lining.
Week 4
Cell division and multiplication continues. Embryo organs start developing as a product of cell division. The digestive organ system starts developing.
Week 5
After the digestive tube forms, the neural tube starts forming. The neural tube will lead to the brain and spinal cord in the grown fetus. It is still too early to detect the embryo on ultrasound at this point. Ultrasound may detect the gestational sac and yolk sac, integral parts of the pregnancy, supporting the growing embryo.
Mother-to-be can start showing the pregnancy at this time, not because of the size of the growing pregnancy, but because she will experience bloating of the abdomen due to the rising levels of hormones. Bloating may subside in the following weeks as hormone levels level and the body normalizes
Week 6
The forming baby is now called an embryo. At this point, the embryo measures about 3 millimeters in length or the size of an apple. The image visualized on ultrasound is called a fetal pole. We call the measurement on ultrasound, the crown-rump length, which measures the fetal pole (forming embryo) from one end to the other. A heart starts beating at this stage. The embryo takes on a C shape, and small buds that will become arms and legs are visible. Eyes, nose, ears, chin and cheeks, also begin to form. The neural tube starts to close
Hormones released by the pregnancy complex create an environment within the uterus that keeps mom from having a menstrual cycle. All energy in the area is dedicated to forming the baby. The same high levels of hormones make mom feel “not like yourself”. Some call it feeling pregnant, some simply call it feeling ugh! Regardless, nausea, vomiting, tiredness, mood changes may all hit you at once or at different times. If you don’t feel any of those symptoms, don’t worry, everyone’s reaction to rising levels of hormones is different.
Week 7
At this point the baby doubles in size from the previous week, to the size of a blueberry. Arm buds develop into paddles and leg buds stretch as well. Brain cells are multiplying at an astronomical rate of over 100,000 cells per minute. The amniotic sac or bag of water forms and encloses the baby, creating a cushion against extra abdominal and pelvic pressure. It also allows the baby room for growth.
Week 8
The head and the trunk are beginning to straighten out, forming a C. Your baby is moving at all times, even though you don’t feel it yet. All extremities show distinct and recognisable joints. The hands and feet are not pads anymore. Digits are developing, although still webbed.
Your baby finally looks human. Features like eyes, which are shut, and the beginning of lips and a tongue in the mouth make your baby look like the human being that he or she is.
Your baby’s heart beats at 150 to 170 beats per minute.
Your baby now measures about 1.5 cm and weighs about a gram, which would make a comparison to a raisin, fair.
Most moms continue to feel very tired, fatigued and feel like the pregnancy is sucking all their energy. Nausea and vomiting may continue through the following few weeks.
Hormones make cause you to produce an excessive amount of saliva with an unpleasant bitter taste, called ptyalism
It is most important to hydrate well during these early weeks because the blood volume is increasing and blood pressure is decreasing, therefore avoiding passing out or dizziness.
Week 9
The end of the second month means that the baby has finished the first stage of life and has graduated from embryo to fetus. Like all great sculptures, the basic shape is formed and now is time to work on details and this means that the baby continues to acquire more human physical characteristics. The eyes irises are in place and can function, but the eyelids are still sealed. The tongue has developed functioning taste buds. The external ears are formed and inner ears are now filled with fluid. As major internal continue to develop, the reproductive reproductive organs are beginning to form. It’s way too early to find out the sex of the baby, but the baby already knows his or her own sex. The liver, spleen, pancreas and gallbladder are forming. Your baby has doubled in size and you can compare to the size of a grape or cherry. The head is about half the length of the baby’s entire body length. Muscles are beginning to develop and extremities have spontaneous movement. As fingers growing longer and webbing disappears, the hand is shaping into the form of the final masterpiece.
In the meantime, mom’s mood swings may be reaching a pregnancy all time high. These sudden changes in the way that you feel are caused by a multitude of factors like, physical stress, fatigue, changes in your metabolism, and hormonal changes. Mood swings peak around this time and return consistently in the third trimester.
It is my firm opinion that we are what we eat and nutrition definitely controls your health. Even if you consider yourself a healthy eater, cravings, mood swings, fatigue and the pressure to feed your baby probably got to you and you may be developing some bad eating habits. At this point, you may be having a hard time fitting into you tight clothes. It’s ok to give in to cravings once in a while, but remember that you don’t have to eat for two. Be very careful with your diet. Nutrition is found in vegetables, salads, lean meats and fish. Whatever you do, don’t diet and remember to take your vitamins, iron and folic acid supplements.
Week 10
Your masterpiece is about the size of a strawberry, about 3 cm in length top to bottom and weighs around .15 ounces. Size has doubled in about three weeks. Your baby is very busy continuing to functionally develop arms and legs, which now have acquired bone and cartilage and are busy practicing their kicks. Your don’t feel movement, but at this point the baby can kick.
Vital organs have fully developed and begin to function. The jawbones develop at this time and all future milk teeth are in place. The baby even practices swallowing, even though all nutrition comes in through the through the umbilical cord. Externally, fingernails and hair are starting to appear.
The heart has completely developed and is fully functional at this point. Heart beat averages 160 beats per minute. The stomach produces its digestive juices, kidneys produce urine and the male reproductive system produces testosterone.
While some first trimester symptoms may be subsiding, others begin to show.
Morning sickness may improve but usually continues throughout the first trimester. Breasts continue to get stimulated by hormones in preparation for breastfeeding. They probably have gotten bigger and may feel engorged. The amount of work that your body is performing behind the scenes is gigantic and it reflects in how tired you feel. Have a little faith in mother nature, it gets better in the second trimester.
The volume of circulating blood continues to increase and requires that you continue to increase your hydration. Varicose veins may show during this week. The best way to avoid those visible blue streaks showing through the skin is to stay active and avoid sitting or standing for long periods of time.
Week 11
The baby’s body growth is catching up to the head and they become about equal in size during this week. Baby’s skin is transparent and allows veins to show.
Arms and legs continue to develop their functionality with kicks continuing as bones get harder and muscles grow. The baby kicks, stretches and can clench his or her fists. You still can’t feel any of these movements. The diaphragm, the layer of muscle separating the lungs from the abdomen, forms and develops enough during this week to cause the baby to hiccup.
The digestive tube muscles now start contracting and practice the movement that will help your baby push the food through later in life.
Hopefully, morning sickness, nausea and vomiting are subsiding by now. Although rarely, these symptoms continue throughout the pregnancy, most times they end with the first trimester. Hormones continue to cause undesirable changes to your body like constipation and heartburn. Continue to adjust your diet to avoid these symptoms. Hydration, avoiding fatty foods and eating small portions help in general. Everyone has a specific food that causes heartburn, avoid it.
The next task that your body performs starts during this week, the making of the placenta, which will feed the baby for the rest of the pregnancy.
Clothes will probably feel tighter around the waist. Although bloating probably subsided, now the baby and uterus are starting to grown beyond the capacity of the pelvis and into the abdomen.
Week 12
Baby’s organs and systems are fully formed. Head and neck continue to straighten during this week giving your baby a less curled up posture. As the face grows and the eyes move from the sides to the front, the face acquires natural human features.
Extremities continue to grow. Fingers and toes stretch out and taper into a shape that approaches the final product. Hiccups continue and the baby uses amniotic fluid in the lungs to start developing this vital organ. Kidneys secretions flow through fully developed ureters and bladder and end up in the amniotic fluid, eventually forming the majority of the fluid within the amniotic sac. Urine is not only harmless, but useful to the growing baby.
Fingers, eyelids and mouth develop reflexes causing them open and close.
Your baby is the size of a lemon, measuring about 1.5 inches and weighs a quarter of an ounce.
Mom’s fatigue, nausea, vomiting and mood swings all continue to happen during this week, but be patient that you are one week closer to the second trimester, when all improve or subside.
Leg cramps may show at night and interfere with your much needed sleep. The combination of hormones, dehydration and electrolyte imbalances causes muscles to tighten painfully. It may sound like a broken record, but the solution again lies within your diet. Increase hydration, drink sports drinks that increase your levels of sodium and potassium. Bananas and broccoli also help. Magnesium salt warm baths also help relax your muscles.
Pigmentation of your skin increases and one morning you may wake and notice darker areas in different parts of your body. Don’t be alarmed, it’s a normal side effect of the increase levels of hormones. Linea nigra, latin for black line, is a dark streak that runs vertically along the midline of the abdomen, from the pubic bone to the belly button, but can extend to the top of the abdomen. In addition to this line, freckles, scars, nipples, genitals, thighs and arm pits may also become darker.
Week 13
Congratulations!! You just made it through the first trimester of pregnancy. Lanugo, thin, soft hair, usually unpigmented cover the baby’s entire body and keeps the baby warm. By this week, the sense of smell of the baby has developed as neurons connect the already developed olfactory bulbs in the nose of the baby to the brain. It’s amazing that at this stage the baby may already start recognizing your by your smell. Taste buds are developed and also connecting to the brain, making them functional.
A males genital organ is formed and functional as well as a girls ovaries already carry about 2 million eggs.
Ears have developed by this week to the point that the baby may be able to hear your voice and your favorite songs. Talk to your baby.
As your body transitions from the first to the second trimester, your fatigue and tiredness may be replaced by a burst in energy. It’s time to get back into a workout routine. Just remember to follow the following simple rules to protect yourself and the baby.
Keep your exercise routine to low-impact exercise, no jumping.
Stay hydrated
Be careful not to fall. You may lose your balance easier because the pregnancy shifts your center of gravity.
Ease back into a routine. Don’t try to catch-up in one week.
Have fun!
Your cervix may become very sensitive and you may experience spotting or bleeding after sex. Call us and make an appointment as soon as you notice. Spotting and bleeding should always be evaluated by a provider to determine the cause and to take necessary precautions.