Embryonic Development Stages

Your baby will start off as a miniscule fertilized egg and grow to a small human being who is able to survive outside of your body. All these amazing developments will take just nine months. And before you know it, your child will be born and you'll be have the opportunity to try early learning methods to stimulate your baby's mind.

The Beginning

The earliest stage of your unborn child's life will be as a zygote or fertilized egg. By week four, around the time you might be able to get a positive pregnancy test, your baby will be a blastocyst as it implants in your uterus. Week five is the beginning of the embryonic development stage and this stage will last until week eight.

Embryonic definition is the first two months of your baby's life in utero. Your unborn child go through vast changes during these two months and will continue to grow throughout your entire pregnancy. Perhaps the most astonishing stage of pregnancy is that of the embryonic development as your unborn child goes from being the size of a sesame seed and looking like a tadpole to being the size of a kidney bean with some neck definition and tiny webbed fingers and toes.

Embryonic Development Stages

Your baby is considered an embryo from week five to week eight of your pregnancy. Chromosomes have already developed to determine your baby's gender at week five, but you won't be able to tell until sex organs become visible in an ultrasound. Your baby is made of three layers, the endoderm, the mesoderm and the ectoderm, that will soon form into her tissues and organs.

The top layer is the ectoderm and this is where your infant's spinal cord, brain, nerves and spine will grow. This is also where tooth enamel, mammary and sweat glands, skin, hair and nails will grow. The mesoderm, or middle layer, will be where the under skin (subcutaneous) tissue will form as well as your baby's cartilage, muscles and bone. The third layer, the endoderm, will be his rudimentary urine system, pancreas, thyroid, liver, intestines and lungs.

By week six your baby has grown to be the size of a lentil. An ultrasound can pick up his heart which will beat at about 100 to 160 times a minute. The first time you see and hear your baby's beating heart it will be like embryonic music to your ears! Blood is beginning to go through his body now and the pituitary gland is starting to form.

At week seven your baby will still have a small tail. This small tail is an extension of her tailbone and it's the only thing on her body getting smaller. Everything else is growing and your embryo is now the size of a blueberry. This is double the size of the previous week. Eyelids are starting to form and brain hemispheres are starting to grow. Her liver is beginning to produce red blood cells until bones are formed and the bone marrow can take over this task.

The final week of the embryonic stage is week eight. The tail is almost gone and your baby is very active and is swimming around in the embryonic fluid. It's now possible to see a hand and knee joints on an ultrasound although you will probably need a skilled technician to point out those spots to you. Your baby will also now be able to automatically reflex to certain types of stimuli. Week nine will be the beginning of your baby's life as a fetus.

Embryonic Review

Here's a look, in a nutshell, of your baby's life as an embryo. The embryo stage starts at five weeks gestation and is finished at the end of the eight week. Sometimes even before you know you're pregnant your baby's heart will be beating. By the end of the embryonic stage your baby will have more than doubled in size.