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 Amazing! There simply is not another word worthy to describe the development of your baby! Just think, within approximately a 40 week period, your little one will have transformed from a single cell to a fully formed human -- filled by wonderment and prepared to change your world forever.
The first trimester (0 - 14 weeks), is one of the most crucial for your baby. Within this trimester you will find the most rapid rate of growth and development taking place. By the end of the 1st trimester, your son or daughter will have grown to 3.4 inches (8.7 cm) long and weigh about 1.5 ounces (43 grams). Your infant will develop everything from limbs to vital organs. Week by week the changes are astounding! Click below to see what's happening with your baby now!
Weeks from Last Menstrual Period
Week 1 |
Week 2 |
Week 3 |
Week 4 |
Week 5 |
Week 6 |
Week 7 |
Week 8 |
Week 9 |
Week 10
Week 11 |
Week 12 |
Week 13 |
Week 14 |
Weeks 15-28 |
Weeks 29-40
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Weeks One through Four
- Ovulation occurs - The time is right; now you just need this egg to be fertilized!
- Conception occurs - Did you know that during your pregnancy that your uterus will increase its capacity by 1000 times?!
- Gender is determined - Immediately upon fertilization your little one is set as a boy or a girl. Ladies, this is one that you can't take credit for since it is up to the sperm to determine the sex of your baby. Sperm carries either a "X" (girl) chromosome or a "Y" (boy) chromosome. (*Hint:* You will have to hold off on picking out the pink or blue until at least the second trimester when the gender will be visible via ultrasound.)
- Implantation - Some spotting (also known as implantation bleeding) may occur about 10 - 14 days after conception. You may believe you are starting your period but generally this bleeding is extremely light and lasts only a day or so.
- Neural tube forms - It will develop into the nervous system (Brain, spinal cord, hair, and skin). Already your baby has the foundation for thought, senses, feeling, and more!
- Heart and primitive circulatory system rapidly form - While still in its beginning stages, this is the very life support system that will carry your child throughout his or her life.
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Week Five
- First heartbeats begin - If you have an early ultrasound you may not be able to recognize this tiny being as a baby, but there is no mistaking what it feels like seeing your child's heartbeat on that screen. That rhythmic beat is echoed in your own heart.
- Umbilical cord develops - This is your baby's lifeline in utero. It bears the responsibility of pumping in oxygen, removing waste, and supplying the necessary nutrients for the remainder of your pregnancy.
- Blood is now pumping - All four heart chambers are now functioning, insuring your baby's body will receive all it needs over not only the remainder of your pregnancy but throughout life.
- Most other organs begin to develop - Your infant's lungs start to appear, along with her brain. Already your little one is preparing for a quest for lifelong learning!
- Arm and leg buds appear - While they may not appear to be much at this stage it is ok to dream of the future. Just imagine your ballerina twirling and jumping around your kitchen floor. Or perhaps you will have the precocious boy that throws the perfect pitch -- right through the neighbor's window.
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Week Six
- The arms and legs continue to develop - These limbs are stretching out more and more. Later on you will be feeling those feet and elbows up close and personal right in your bladder!
- Brain is growing well - Did you know that over the course of the remaining months that your baby's brain will develop over 100 billion neurons? This is just the beginning!
- Lenses of the eyes appear - If you could catch a glimpse inside, you would notice your baby's appearance becoming increasing like a newborn's.
- Nostrils are formed - The position of the nose seems to shift into its proper place as well. Soon, the nerves running from the nose to the brain appear.
- Intestines grow - Initially these are actually located outside the baby's body within the umbilical cord.
- Pancreas - Your baby is now equipped to deal with digestive enzymes and take on processing the insulin and glucagons the body needs to function.
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Week Seven
- Elbows form - Again, taking a peek inside you could see your baby's fascination with bending and flexing. Later you will swear you can enlist your child as the star of the next "Karate Kid" movie!
- Fingers start to develop - These digits often become your baby's first toy!
- Feet start to appear with tiny notches for the toes - It is fascinating that at less than a half inch, your little guy (or gal) already is leaving "footprints" on your heart!
- Ears eyes and nose start to appear - Although they may resemble an alien life form, these all "shift" soon enough into a more normal appearance.
- Intestines start to form in the umbilical cord - Did you know that initially the intestines are not formed inside your baby's body?
- Teeth begin to develop under the gums - Thankfully, right now you won't be dealing with teething pain!
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Week Eight
- Cartilage and bones begin to form - At the end of this week your baby will have already completed 1/5th of the journey 'til his birthday!
- The basic structure of the eye is well underway - The position is more "newborn" like already!
- The tongue begins to develop
- Intestines move out of the umbilical cord into the abdomen.
- Body grows and makes room - Two months along and this little one is growing inside and out by leaps and bounds!
- The fingers and toes have appeared but are webbed and short
- Baby's length (crown to rump) is 0.61 inch (1.6cm) and weight is 0.04 ounce (1gm)
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Week Nine
- Baby has begun movement - While still too small for you to feel, your little one is wriggling, shifting, and dancing already! Makes you almost wish for a window to peek in whenever you want!
- Most joints are formed now - and trust that your little one is practicing bending and flexing.
- Fetus will curve its fingers around an object placed in the palm of its hand - This is amazing to see! At only nine weeks, if you happen to have an ultrasound, you may observe your infant fascinated by everything he or she can lay their fingers on (mainly other fingers, toes, ears and nose!
- Fingerprints are already evident in the skin
- Average size this week -- length 0.9 inch (2.3cm), weight 0.07 ounce (2gm)
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Week Ten
- Baby is now called a fetus in "medical terms". You, however, may have chosen the name "peanut," "angel," "jumping bean" or simply "miracle."
- The most critical part of your infant's development is complete. Now you are headed into a period of rapid growth.
- While a bit strange to envision, your baby's head is now about half its length - Soon the rest of the body's growth will catch up but this area is prepared to keep up with the rapid brain development!
- Eyelids fuse shut and irises begin to develop - Eye color is also determined by this point.
- Placenta begins to function this week or next - The placenta is the organ responsible for both the provision of nutrients along with the removal of waste to keep your baby growing strong!
- Your baby will be about 1.22 inch long (3.1cm) and weigh 0.14 ounce (4gm) at the end of this week
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Week Eleven
- Nearly all structures and organs are formed and beginning to function.
- Fingers and toes have separated - Take a glimpse at how incredibly precious your child's tiny feet are at this point.
- Hair and nails begin to grow
- The genitals begin to take on the proper gender characteristics - It will be just a few more weeks before your ultrasound can show if you are having a boy or a girl! Have you been dreaming of pink or blue?
- Amniotic fluid begins to accumulate as the kidneys begin to function - This fluid, consisting primarily of water, helps provide a cushion for your baby while she's nestled within your womb.
- The muscles in the intestinal walls begin to practice contractions that digest food.
- Your baby is about 1.61 inches (4.1 cm) long and weighs 0.25 ounce (7gm).
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Week Twelve
- Vocal cords begin to form - While perhaps not quite ready to be introduced to the nearest opera stage, your infant will use these immediately following the moment of birth. Bet you can't wait to hear that first cry!
- Those precious eyes begin to move closer together - Are you wondering if he will have mommy's crystal green eyes, daddy's laughing brown ones, or maybe out of the gene pool will emerge grandma's clear blue!
- Ears shift to their normal place on the side of the head
- Intestines move farther in to your child's body
- His or her liver begins to function - Responsible for cleansing the blood, storing nutrients, and providing needed chemicals, this is an important event!
- The pancreas begins to produce insulin
- Guess what? Your baby's average size is now at a whopping length: 2.13 inches (5.4cm) and weight: 0.49 ounce (14gm)
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Week Thirteen
- Your infant is about 2.91 inches (7.4cm) and weighs around 0.81 ounce (23gm) - This is about the same weight as 4 quarters.
- If you could peek in again you may spot your baby as he begins to practice inhaling and exhaling movements
- Eyes and ears continue to move and develop
- Baby's neck is getting longer, and the chin no longer is resting on his chest
- Her hands are becoming more functional - Your baby may find it comforting to start playing with her fist.
- At this point all nourishment is received from the placenta
- On your next doctor visit you should be able to hear heartbeat with a Doppler by now - (Don't worry though if you can't, the heartbeat can be confirmed through U/S). Your baby's heartbeat is much rapider than your own and may remind you of the race towards birth that he is running!
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Week Fourteen
- Thyroid gland has matured and your baby begins producing hormones which will be used throughout his or her life.
- In boys, the prostate gland develops
- In girls, the ovaries move from the abdomen to the pelvis
- Your little one may have learned to suck his thumb by this point!
- Your child's bones are getting harder and stronger by the day!
- Your baby's skin is very transparent still
- Lanugo (very fine hair) covers the baby's body and will continue to grow until 26 weeks gestational age - Generally this will be shed prior to birth. Its purpose is to help protect baby's skin while in all that water!
- Your baby is 3.42 inches (8.7cm) long and weighs about 1.52 ounces (43 grams) - approximately the weight of a letter!
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3d ultrasound images reprinted with permission from Eco-3d and SonoPortal. Embryoscopy and fetoscopy photos appearing on this web site are reproduced under "fair use" uterms for the purpose of public education.
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