The first month of pregnancy marks the beginning of the whole process, the gestations starts with the fertilisation of the egg by the spermatozoid. Once fertilisated, the zygote (cell embryo)is formed the cellular splits take place by degrees. During the first week an important event happens: implantation.
From fertilization to implantation
Embryo implantation is the attachment of the embryo to the endometrium (inner layer of the uterus). Once the embryo is implanted a new process of multiple splits and developments commences, slowly forming what one day will be a human being.
Pregnancy is a long process and both the woman and foetus go through several changes. Not just physical changes that can be observed with a naked eye (enlarged belly, breast increase…), but emotional and perceptive, as well as other non-visible symptoms that affect the mother and the baby.
During the first weeks, the unborn will start to develop its taste and deglutition. It is a process that later, during birth and for the rest of his/her life, will help his/her digestion. Despite taking place during the first weeks, the process will last far beyond the first month.
The first day of the last period is considered to be the first day of pregnancy. It is hard to know when the embryo has been implanted into the uterus. That’s the reason why the week of the last period tends to coincide with the fist week of gestation.
In this initial week, your egg, after being reached by the spermatozoid, splits until forming a sphere called blastocyst, that may contain up to 100 cells in the first 4 days, until they start to divide into two groups in the fifth. The exterior group will form the placenta, while the other will become the embryo, later to be called foetus, and after the gestation is over, will be a baby. These inner cells are known by the name of mother cells, able to transform into cells of any part of the organism, being more than 200 different types.
At the end of the week the egg will have traveled to the uterus. It will be placed in this location for the remainder of the gestation.
During this week the ovarian follicle recruitment and follicle selection take place. Some primordial follicle star to growth, until becoming primary follicles. Nonetheless, only one will be picked, the follicle with the highest response to the FSH hormone.
The dominant primary follicle will keep its development,while the others will cease it and will experience atresia. The uterus gets ready for the future coming of the embryo, its wall thickening.
Although is still soon for the nervous system and other important organs to be formed, some laying foundations of these more complex structures, that will develop in the near future, start to flourish. In fact, ears and eyes do enter in the primary formation phase during the second week.
The budding mother’s blood volume has a 50% increase, due to the oxygen demands of the embryo and the formation of the placenta, a safe place for embryo to grow.
The follicle is detached form the follicle and the fallopian tubes catch it. The oocyte will finish its maturation, thus becoming an egg.
During its trip to the uterus, the egg is maturating and the genetic material of te spermatozoid is blending with the egg, resulting in the genes the baby will be composed of. After 24 to 40 hours, the embryo will be divided in 2 cells, after splitting into 4, an so on until forming, in the fifth day, 100 cells.
There’s already a heartbeat in the heart of the future baby, with an average of 150 beats per minute, though the mother will have to wait until the fourth month, approximately in 12th week, to hear its heartbeats (using a stethoscope)
Once the soon-to-be mother reaches the third week, she will notice some symptoms that will create some discomforts, such as dizziness, nauseas, she also will be visiting the toilet more often. All these multiplied cells are stimulating embryonal growth. From now then, the bigger the embryo is, the more discomforts will originate in her carrier, as it is starting to apply pressure on the belly and some of her organs.
The blastocyst floats in the uterus for some days. The embryo is growing 1 mm a day, and now has the size of a bean, approximately. The embryo is a tiny circular saucer of 2,5 mm diameter.
The eyes are two big black dots and what one day will be its limbs (legs, arms), are now little bumps.
It also time for the nervous system, heart, skeleton and muscles to develop at a faster pace. The tissue of its face is also being formed. Hair also grows during this week.
Regarding the mother, frequent urinating and morning sickness will increases, and she might feel more tired and sleepy than usual.