An Embryo Forms: Weeks 4 to 8 of Pregnancy | Parents

An Embryo Forms: Weeks 4 to 8 of Pregnancy | Parents

In the fourth week of your pregnancy, the
ball of cells that is developing into your baby is
the size of a poppy seed. It’s at this stage that the
cells separate into 3 distinct layers from which your baby’s
internal organs and skin will develop. The outermost layer forms
the brain, nervous system and skin. The middle layer forms
the heart, blood vessels, bones, muscles and reproductive system. The
innermost layer will develop into the stomach, intestines, lungs, and
other organs. Your baby’s first blood cells are already being
produced in the yolk sac. Expect big changes by the
fifth week of your pregnancy. The ball of cells now
resembles a tadpole and it is big as a peppercorn. The creation of the brain, spinal cord, heart,
and blood vessels is already well under way. The neural
tube, which will form the brain and spinal cord starts
to close from the center of the embryo outward. After
it closes, the portion in the head thickens and divides
into the forebrain, midbrain, and hindbrain. Rapid
growth causes folding of the embryo. During this process, part of the yolk
sac is incorporated into the lining of the digestive
system. The primitive backbone is curled and looks like a tail,
which will recede in a few weeks. Your baby’s heart is
transformed from a tube into an S-shaped loop that begins
beading about 22 days after conception. At this point,
you may begin experiencing early signs of pregnancy
including nausea, fatigue, and breast tenderness. By your sixth week of pregnancy,
your little one has tripled in size and is protected by
amniotic fluid. The baby is grown by leaps and bounds,
but still only about the size of a lentil. You’ve
just been to the OB/Gyn and she is confirmed the
good news. You’re definitely pregnant. You don’t
know if you’re having a boy or a girl yet, but you can thank
dad for your child’s sex because one of two sex
chromosomes either an X or a Y was delivered by
the sperm determining your child’s gender. The egg always contains
an X so if the sperm contained an X, the embryo develops into a girl. But if the sperm
contained a Y, the embryo develops into a boy. A gene
on the Y chromosome becomes active late in the sixth
week, functioning for only a few days to tell the
embryo to become a boy. Facial features have formed and
his heart has a regular rhythm pumping fetal blood. Right
now because your baby’s skin is only one cell think,
it’s transparent. Little knobs protrude from the embryo’s trunk. These
buds of tissue will become arms and legs. At the
beginning of your seventh week, your baby is now about
the size of a coffee bean. The umbilical cord connecting
your baby to the uterus is now visible. The placenta
is covered with lots of small projections called villi. The
villi from the placenta intermingle with your blood where they
steal some of your breakfast, lunch and dinner. The nutrients
and oxygen travel about 18 inches through the umbilical cord
to your growing baby. It’s too early to tell whether
your child will have your nose, but mouth, nostril and
ear indentations are visible in the head. The arm buds
that form last week look like paddles. The brain is
growing rapidly including the right and left sides of the
brain. The right side of the brain is associated with
nonverbal and spatial tasks. The left side is associated with
speaking and writing. You’ll have to wait and see if
your child becomes predominantly right or left brain. By the
eight week, your fetus is about the size of a
blueberry. What were once just little tissue buds have become
recognizable as hands and feet with webbed fingers and toes.
Soon, this extra tissue between the digits will be reabsorbed
to reveal individual fingers and toes.


  1. my daughter is 8 weeks. she has been really sick. she has one daughter three miscarriages. we are going for an ultra sound in three days and we are both scared to death. pray for us

  2. 6weeks & 5 days today. First dr appt is tomorrow with an Obgyn. #ExcitedMuch & love & bliss to you and yours.

  3. i found out this week that im having my first baby i'm afraid and happy at the same time i just want my baby to have what he or she needs and not mess up

  4. Just found out today I am expecting my 2nd baby! Such an amazing journey we have and go through! Such a blessing!!! ❤️

  5. I just found out I'm pregnant with baby #2! I'm so happy after trying for over 2 years after miscarriage. May God Bless everyone posting their exciting news.

  6. I am so happy after my wife gave me the good news of expecting our 2nd baby after almost 10 years of trying. At this stage, i just want this baby to come out healthy. It don't even matter the sex. Our daughter doesn't know she will have company soon. As a girl, she wants a baby sister. But my wife wants to give our daughter the news for her birthday on may 21st. People, get ready to see me cry,too. God bless you all for all these blessing over you.

  7. 5 weeks with baby #3 😀 so excited im like a kid on sugar lol ♥♥ after 2 boys hope its a girl but as long as healthy and safe ♥♥

  8. It makes me happy to see all of these woman saying they're pregnant but kind of makes me sad because I have been trying for almost a year with my boyfriend and nothing has happened yet :/

  9. I am 6 weeks and 4 days….I am nervous but happy. We miscarried 8 months ago and kept trying then stopped trying and concieved that month! want to tell anyone that may be worried to just enjoy your mate. The one month we didn't track my ovulation we got pregnant

  10. I am kow 6 weeks and 2 days !:) I am so excited, as this is my first and it took us 8 years to conceive! I can't wait to meet my little miracle.😍

  11. The mother determines the child's gender. She gives X automatically. He has to provide a y to change her mind. The female is the first sex

  12. And you're talking about a stage that I don't want to hear it. If I wanted to hear that part I would have got done a different video. This thing is it sterile s***.

  13. I found out that am pregnant on the 22nd of this month, this is my first baby and I'm two weeks pregnant

  14. Helpful video to review before embryology exam, but incorrect. Not a baby. Not even a fetus. It's an embryo. Not a baby. Not a child.

  15. I’m 5 weeks and 3 days with my first baby 😭🥺❤️🙏🏽 I’m very nervous and excited at the same time!

  16. I’m excited the father still in shock.we had sex multiple times took morning after pill STILL turned up pregnant 😥. ALL babies are blessings. With GOD I’ll be alright 😌

  17. My last menstruation was last january 8-11 but today is february 17 and still waiting for my mens to visit .can anybody tell me if i am pregnant or not

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