Fertilization and implantation

| The fertilization of the ovum is produced by the entry of part of the sperm into its interior at that moment the ovum forms a layer around it that prevents fertilization by a second sperm. This process occurs in the fallopian tube and on cycle day 14 in a woman with regular periods.

The cell resulting from the union between egg and sperm it is called zygote. This is transported through the Fallopian tube while cell divisions begin and therefore their growth. When dividing the zygote it passes to the morula stage. At this time it reaches the uterine cavity where the endometrium has already been prepared for its reception and subsequent implantation. The implantation occurs on day 7 after fertilization and the morula has already passed to the next stage, that of the blastocyst.

The first 10 weeks after fertilization the embryo develops and later it will be called a fetus. The blastocyst cells give rise to both the embryo and the adnexa (placenta, umbilical cord, amniotic sac)

First weeks of pregnancy

• In the week 3 After fertilization, the yolk vesicle is formed, which is already visible by ultrasound and the embryo is a small 2-3 mm thickened disk in the same yolk vesicle.
• In the week 4 post-fertilization the embryo is already about 5 mm and has a heartbeat.
• In the week 5 the embryo begins to bend and the umbilical cord can be seen by Doppler ultrasound.
• In the week 6 After fertilization, the embryo measures between 18 and 25 mm and the brain, spinal column and limb buds begin to form. You can begin to visualize movements of the embryo by ultrasound.
• The week 7 post-fertilization the extremities develop and the bones of the face begin to form, it measures between 25 and 35 mm.
• The week 8 post-fertilization the embryo already measures between 35 and 45 mm. The hands and feet are formed and the embryo begins to have a human form.

At 10 weeks post-fertilization, 12 weeks since the date of the last menstrual period, the embryo already has human form, with fingers and toes, and a 12-week ultrasound was performed with the measurement of the nuchal fold. Various internal organs such as the stomach, brain, urinary bladder or kidneys can be seen by ultrasound. It measures about 60 mm from the head to the rump, after which it is then called fetus.

What happens during the second trimester of pregnancy? Find out.