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From Embryo to Fetus


Every future mom is interested to know how her baby develops, what he looks like and what he can do at different stages of pregnancy. Currently, thanks to the existence of such a diagnostic method as an ultrasound, the expectant mother can get to know her baby before birth. Let’s examine the development of the embryo by weeks and months.

Stages of development of the human embryo

It is worth saying that the prenatal development of a person can be divided into two periods: embryonic and fetal.

The embryonic period lasts from the moment of conception to the 8th week of pregnancy, when the embryo acquires human traits and all internal organs and systems. So, let’s review the main stages of development of a human embryo.

The starting point of the development of a human embryo is the fertilization of an egg by a sperm cell.

There are the following periods of embryonic development:

  • The zygote stage is short and lasts until the moment of division;
  • Blastocyst stage. At this stage, active reproduction of cells occurs, as a result of which a tube with a cavity inside is formed;
  • The stage of gastrulation is characterized by the transformation of a single-layer embryo into a bilayer (ectoderm and endoderm);
  • The stage of isolation is characterized by the separation of organs and systems with their further development.

During week three of pregnancy a protrusion forms on the back of the embryo that turns into a neural tube. Cranial thickening of the neural tube leads to the development of the brain, and the spinal cord is formed from the rest of the neural tube. During week four of pregnancy, segmentation of the embryo occurs, the differentiation of tissues and the formation of organs begins.

Embryo development at week five is characterized by the appearance of undeveloped hands.

In the development of the embryo at six weeks, the further formation of the hands and the beginning of the formation of the legs are noted. The development of the embryo at 7-8 weeks is characterized by the formation of fingers and the acquisition of a human appearance.

It is known that among women who smoke and consume alcohol, the embryo lags behind in development.

Stages of fetus development

After eight weeks of gestation, the embryo is called a fetus and its further development continues. During this period the fetus has a weight of 3 grams and a length of 2.5 mm. At 8th week of development, the baby’s heart is already beating and the fetal heartbeat can be seen on an ultrasound.

At 9-10 weeks of development, the growth and development of the cardiovascular system, liver and biliary tract continues, the urinary and pulmonary system is actively formed. At this stage of development, there are already genitals, but they are not yet visible by ultrasound due to the small size of the fetus.

By the 16th week of pregnancy, the length of the fetus reaches 10 cm, the placenta and the umbilical cord are already formed and the baby now receives all the necessary things through them. During this period the fetus actively moves in the uterus, sucks a finger and swallows, but the future mother still does not feel these movements, because the baby is still very small. The pregnant woman starts to feel fetal movements only at 18-20 weeks of pregnancy, when the fetus reaches a weight of 300-350 grams. At six months of development, the baby can already open his eyes. From the age of seven months, the child already reacts to the light, can cry and can feel pain. At eight months of pregnancy, the baby is fully formed and only gains body weight, the final maturation of the lungs occurs.

All mothers are experiencing wonderful feelings during pregnancy; feelings that she will carry through the years. Love, care, patience, compassion and the desire to always be with her child.

The Network of Reproductive Medical Centers (ISO 9001:2015 certified) “Mother and Child” that employs the highly renowned reproductive embryologists and long-standing members of the European Society of Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM) has been successfully involved for over eleven years in practical application of assisted reproductive technologies (ART) and various types of surrogacy programs at affordable cost that resulted in birth of 9,074 healthy children and helped thousands of people throughout the world to find the happiness of parenthood.

Please contact IVF Group Surrogacy Services at +1(213) 277-5874 or visit our website at www.ivf-international.com to find out more or to schedule a consultation with a reproductive embryologist.