Following the ovulation, fertilization and conception taking place successfully; by fourth week the blastocyst is firmly embedded in your uterus. This is the time for more advanced development of your baby. Normally, your body would be getting ready for the next menstrual period by this time; but your pregnancy will trigger new hormonal secretions that will prevent this from happening.
The two week period following your ovulation is known as the luteal phase. Corpus luteum, which is a collapsed follicle that has remained behind after releasing the ovum, plays a major role in the changes taking place in your body during this period. Hence this phase is known as the luteal phase.
The corpus luteum increases the production of progesterone, which in turn warms up your body and uterus for embryo. Simultaneously it thickens the endometrium, and increases the blood supply which creates a soft cushion like condition to catch the blastocyst when it arrives.
Your brain has already been informed by your reproductive system to stop the procedure of menstruation. Your body signifies what is best for your foetus through hormonal signals and triggers.
Another major change you observe in your body is the secretion of hCG (human chorionic gonadotropin)hormone. The level of hCG in your body increases rapidly during the first few weeks of pregnancy; it doubles itself almost every day. This hormone is responsible for detection of pregnancy in pregnancy tests.
By the beginning of the gestational 4 week pregnancy, the blastocyst is comfortably settled in your uterus. Your uterus has undergone enough changes and has made the epithelium of the uterine wall suitable for the reception of the blastocyst. If the endometrial epithelium is not properly prepared for implantation, the blastocyst will fail in attaching itself to it.
The unicellular zygote which was created few days ago now consists of an inner cell masses that constitute embryoblast, trophoblast and a primary yolk sac by the 4th week of pregnancy. The embryoblast will develop into an embryo and the trophoblast will develop into the placenta.
By this time, a second cavity has appeared within the inner cell mass which later enlarges to become an amniotic cavity. Most of cells that make up the amniotic cavity come from inner cell mass, but some cells are borrowed from the trophoblast.
The placenta cells are tunnelling away into the interior lining of your uterus with their microscopic tentacles known as chorionic villi. The placenta may become fully functional by the end of the week, but at present it is unable to provide nutrients or take away the waste produced by the developing foetus.
Slowly the placenta begins to grow and embed itself in the uterine wall. It is made of two distinct layers at this point. The cells of the placenta are implanting themselves and creating space inside the lining of uterus so that there is a channel created for the blood to flow inside the developed placenta.
The amniotic sac will protect the foetus by cushioning it from any possible damaging pressure which may arise inside the womb by keeping it comfortable, in addition to preventing dehydration of foetal tissues. The yolk sac delivers nutrients to the foetus, since the placenta will take time to develop. It also begins to produce the red blood cells.
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Your tiny baby who is now a foetus is establishing its connections with you by growing long projections into the uterine walls. Isn’t that amazing? The tiny little hair like tendrils that enfold around the copious small blood vessels in the lining of your uterus, will develop into a placenta. This is the time when the embryo will develop a membrane around itself which is also the inner layer of the developing placenta.
The membrane known as chorion, establishes a connection between your uterus and your baby, which will continue until child birth. The tendrils provide oxygen and nutrients to the growing foetus until the placenta is fully formed. From now on, you are responsible for providing oxygen and nutrients for the developing baby to survive. It is a great responsibility, but fortunately nature has made every mother fit to carry that duty with natural ease.
Your baby is fast reaching the embryonic stage during the 4th week of pregnancy. Though there has been rapid cell division, all the baby has managed to reach is the size of a pinhead. The epiblast and hypoblast present during this stage will develop into the body and organs of your baby. All the cells in the zygote were identical until it reached the eight-cell stage, but then it started to form into embryonic stem cells. The foetus will start to function by the end of week 4 with the help of the nutrients and oxygen supplied by the mother’s blood.
During 4 week pregnancy, the embryonic stem cells have a choice to develop into any other specialized cell that is required for the baby’s growth. They may develop into nerve cells, blood cells or muscle cells at this stage, but once they become specialized, they have to perform their function exclusively. They cannot change to any other type of cells after this stage. From the stage of identical 8 cells, now these cells can form all the different tissues required by the growing baby.
No matter what the IQ of your child is going to be after birth, at this stage your baby is performing a great task of switching the genes on and off with a high degree of accuracy, precision and complexity. The cells at this stage are called specialized cells because they switch off the genes that are not necessary and switch on the genes that are required to make a specific cell work.
The muscle cells have all the genes except the genes needed to make muscle cell proteins. The same applies to all specialized cells which switch off genes that they do not require for the specific function. The cellular actions of switching on and off the growth factors continues at specific times and locations as directed by the signals sent out by the embryo, or precisely by the genetic code present in it.
Imagine the tiny embryo embedded in your womb that is tuning the signal strengths and turning the switch of the growth factors and receptors on or off according to the requirement, depending on their location. This is one of the greatest miracles of the rapid development taking place inside your womb.
The baby is already establishing its own identity in your womb. Even from the very early stage of your pregnancy, the blood of your body does not mix with the blood of your baby. The placenta pays the gatekeeper in this situation. The vascular network of your baby is developing and performing the functions of transporting blood, oxygen and nutrients from you blood stream through the umbilical cord.
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Finally by the end of the week 4, you baby can be measured, though it is very tiny. The embryo is just a collection of cells measuring 0.4 mm or 1/25th of an inch, but is already functioning like a human being. Imagine the long journey your foetus has taken from being just a hollow ball, with just some cells growing as a cluster within to this stage. That is a giant leap.
Though you are officially pregnant and your baby is growing in your warm womb, it is still too early for signs and symptoms of pregnancy to show. However, if you are fertile and planning on conceiving, you should watch out for early signs and symptoms of pregnancy at 4 weeks; because this is the phase when most of the major development in your baby takes place and also this is time when she is very vulnerable.
Knowing you are carrying a precious foetus may help you make wise decisions quite early in your pregnancy. Here are few signs you may watch out for in week 4, but know that they are highly individualized. Some women experience all the symptoms of pregnancy whereas others sail through their pregnancy with just a bump to show. Do not panic if these signs are present or absent.
When the blastocyst embeds itself in the wall of the uterus, in some women it is accompanied by slight spotting. But if there is no spotting, just know that you are not one of them. Spotting is not necessary during implantation.
If you have a short menstrual cycle, then by the end of week 4 you will know that your monthly visitor has not arrived. Now that you know 4th week pregnancy symptoms, lets see some care and tips.
Week four is the time when the stage is being set for the development of your baby’s heart, head, brain, spinal cord, tissues, hair, organs, teeth, muscles and bones. Your baby has firmly established its connection with you for another 36 weeks. Take care to make the best of the connection and help your baby grow safe and healthy. Here are few tips that would have a positive effect on your pregnancy.
Even after safe implantation in the uterus, the chance of you having an early miscarriage is about 20-30%. So take care of yourself during the fourth week by avoiding activities and food that may felicitate the unfortunate event.
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Article by Farida Rizwan
Copyrighted Pregnancy & Baby by Mummys Market 2019
