Journey with us as we take a look at what goes on in the womb as baby grows in our week-by-week guide.
WORDS RACHEL LIM
The first week is the week of your menstrual period. Your expected date of delivery (EDD) is calculated from the first day of your last period. This week counts as part of the 40 weeks of pregnancy even though your baby has yet to be conceived.
Your body gets ready for ovulation and prepares for fertilisation.
As sperm meets egg in the fallopian tube, fertilisation occurs. The fertilised egg goes through a process called cell division and continues to divide as it makes its way to the uterus. The group of cells now looks like a tiny ball and is known as a blastocyst. At the end of this week, the blastocyst will implant itself to the lining of the uterus. The implantation site eventually develops into the placenta.
Your baby which is now called an embryo consists of two layers of cells— epiblast and hypoblast. These cells will eventually develop into baby’s organs and body parts. The amnion and the yolk sac also develop at this point in time.
Your human Chorionic Gonadotropin (hCG) levels are now high enough to get a positive on a home pregnancy test kit!
Your baby’s heart begins to beat! The beginnings of digestive and respiratory systems are forming and small buds that will grow into baby’s limbs are also appearing.
At this stage, because baby’s legs are curled up against the torso, full-length measurements are difficult and hence they are measured from crown to rump rather than from head to toe.
The umbilical cord is formed. It is your baby’s vital connection to you throughout the pregnancy, transporting oxygen and nutrients to him as well as removing waste.
Baby’s eyes are becoming more obvious because they have begun to develop pigment in the retinas.
The tail of your baby’s spinal cord has shrunk and will almost disappear by the end of this week. In contrast, your baby’s head is growing and it is relatively large compared with the rest of his body. Also, parts of the internal reproductive system, such as testes or ovaries, start to form.
All of your baby’s vital organs have been formed. Congenital abnormalities are unlikely to develop after this week.
The embryo now has a distinctly human appearance and is officially considered a foetus.
In the last week of your first trimester, your baby’s tiny fingernails, toenails, and vocal cords begin to form. His kidneys are also functioning. He swallows amniotic fluid and passes it out as urine.