First Trimester Baby Growth

First Trimester

Week 2
Fertilization, the joining of the sperm and the egg in the fallopian tube to form a unique human being, occurs. Forty-six chromosomes provide the blueprint for the embryo’s physical characteristics.


This picture (above) is a fertilized egg only thirty hours after conception. Magnified here, it is no larger than the head of a pin. Still rapidly dividing, the developing embryo, called a zygote at this stage, floats down from the fallopian tube and towards the uterus.

Week 3
At this point, the blastocyst, or developing embryo, is looking for a spot to implant in the uterus. Early formation of the central nervous system, backbone, and spinal column has begun. The gastrointestinal system has also begun to develop with the kidneys, liver, and intestines forming. The heart has begun to form.

Week 4 & 5

Hormones produced by the embryo stop the mother’s menstrual cycle.The embryo’s tiny heart begins to beat by day twenty-one. The brain has developed into 5 areas and some cranial nerves are visible. Arm and leg buds are visible and the formation of the eyes, lips, and nose has begun. The spinal cord grows faster than the rest of the body giving a tail like appearance which disappears as the embryo continues to grow. The placenta begins to provide nourishment for the embryo.

Week 7

Major organs have all begun to form. The embryo has developed its own blood type, unique from the mother’s. Hair follicles and nipples form and knees and elbows are visible. Facial features are also observable. The eyes have a retina and lens. The major muscle system is developed and the embryo is able to move.

Week 8

The embryo is reactive to its environment inside the amniotic sac where it swims and moves. Hands and feet can be seen. At the end of week 8, the embryonic period is over and the fetal stage begins.

Week 9 to 12
The heart is almost completely developed and the heart rate can be heard on a Doppler machine at the doctor’s office. Most major organs and tissues have developed and red blood cells are now produced in the liver. The face is well formed and the eyes are almost fully developed. The eyelids will close and not reopen until the 28th week. Arms, hands, fingers, legs, feet, and toes are fully formed. Nails and earlobes start to form and tooth buds develop in the gums. Fetus can make a fist with its finger. Testosterone (male sex hormone) is produced by the testes in male fetus.

I love looking at these pics... they are so adorable even when they dont look Human!

I still find it amazing that we come from a single sperm and an egg.. everyone is so unique..
Yes before anyone asks, my mum did tell me about the birds and the bees, but you know what I mean

Yeah sure is amazing.The egg picks the sperm too,did you guys know that?

Yeah i heard something about the egg picking the sperm but exactly how does it do that do you know?

I would love to know how Doctors find out things like that! I mean my eggs must be really fussy about choosing their sperm, 6 months and still no takings. Come on ladies! :scratch:

Oh I didnt know you were trying... Just think though when your baby comes out you can tell her she/he has to be the best! -lol-