4 Weeks Pregnant - What to Expect

See the incredible journey from fertilization to implantation and learn about the crucial role of the placenta in the early stages of pregnancy. Learn more about week 4 of pregnancy: https://www.whattoexpect.com/pregnancy/week-by-week/week-4.aspx Track your baby's growth with the What to Expect App: https://wte.onelink.me/85iI/29dt1g98 Transcript: It's implantation time! Now no bigger than a poppy seed, the ball of cells that will become your baby has completed its voyage down your fallopian tube and has docked itself in your uterus, tunneling into the sticky uterine lining where it will stay connected to you until delivery. Once in place, about six to 10 days after fertilization, the blastocyst undergoes the great divide, splitting into two bundles of cells. The inner bundle will become your baby, while the outer bundle will borrow deep into the wall of the uterus to become the placenta, your tiny one's lifeline throughout your pregnancy. Some of those placental cells will form an outer layer of membranes called the chorion. Other cells will form the amniotic sac, which will fill with fluid to cushion your baby, now promoted to embryo as he or she grows. And finally, you'll have the sign you've been waiting for, a positive pregnancy test, courtesy of the pregnancy hormone hCG generated by the developing placenta. That, of course, and you'll miss your period. Though your embryo is only a tiny dot, it has already started to differentiate into three layers, each with its own job assignment. The inner layer, called the endoderm, will become the digestive system, liver and lungs. The middle layer, the mesoderm, will grow into the heart, sex organs, bones, kidneys and muscles. The outer layer, called the ectoderm, will develop into the brain, nervous system, skin, hair and eyes. It's hard to believe, but by the end of the fourth week of pregnancy, all the building blocks for your baby's vital organs are firmly in place, with of course, a whole lot of growing to go.

الفئة