4 weeks pregnant
Your developing Baby-
Implantation of the embryo into the wall of the uterus is a common feature of all mammal and in humans occurs six or seven days after fertilization i.e when you are 4 weeks pregnant. Successful implantation requires a receptive endometrium that has been appropriately primed with estrogen and progesterone.
When you are 4 weeks pregnant, development in your baby started rapidly. In 8th day postfertilization, the formation of the human placenta begins. Primary functions of a placenta are the transport of oxygen and nutrients between the fetus and mother.
by the 10th day the blastocyst becomes totally encased within the endometrium. It measured only 0.36 by 0.31 mm
The mesenchymal cells within the cavity are the most numerous and eventually will condense to form the body stalk, which serves to join the embryo to the nutrient chorion and later develops into the umbilical cord.
The neural tube – from which the brain, backbone and spinal cord, and nerves will sprout – develops in the top layer. The heart and the circulatory system begin to appear in the middle layer. The third layer starts to house the lungs, intestines and beginnings of the urinary system. These all development started in your baby when you are 4 weeks pregnant, but even you don’t know that you are pregnant.
This week your baby continues to implant in your uterus, burying itself deep within the endometrium. Once implanted, your baby starts to produce a hormone called human chorionic gonadotropin (hCG), which helps to maintain the lining of the uterus. It also sends a signal to the ovary to stop releasing an egg each month, which stops your monthly periods.
Early Sign when you’re 4 weeks pregnant – Some women experience slight cramping and spotting of blood during this week while implantation is taking place, and they may mistake this for a period, as it often occurs around the time their monthly period was due.
- Einat L.K. Pregnancy week by week : Pregnancy Guide: Voices from the womb. Speedy Publishing LLC, (2014). ISBN 1633833291.
- F. Gary Cunningham, John C. Hauth. WILLIAMS OBSTETRICS – 22nd Ed. (2005). The McGraw-Hill Medical Publishing Division. p.33 . ISBN: 0-07-141315-4.
- Glade B. Curtis, Judith Schuler (2011). Your Pregnancy Week by Week (7th Ed). Da Capo Press, 2011. p. 1-24 ISBN 0738215422
- Laura Riley. You & Your Baby Pregnancy: The Ultimate Week-by-week Pregnancy Guide (1st Ed.). Meredith Books (2006). p.14
- NHS. The Pregnancy book. ebook. (2009). p.6
- Paula Spencer, Cindy Luu. Pregnancy Journal: A Week-By-Week Guide to a Happy, Healthy Pregnancy. Peter Pauper Press, Inc., 2006. p. 11-15. ISBN 1593594364.