By Sally Robertson, BSc
During the very first trimester of pregnancy, a baby goes through several stages of development, beginning as a fertilized egg after conception then creating in to a blastocyst, an embryo then a fetus.
The growth and progression of a baby up to eight weeks of pregnancy are described in much more detail below.
Senior doctor going through woman’s pregnancy scans – Image Copyright: Rocketclips, Inc.
Weeks 0 to 4
During the very first two weeks of the moment that is called pregnancy, a woman is not in fact yet pregnant.
Conception generally takes put around two weeks after the very first day of a woman’s last period and doctors consist of the moment from that very first day as section of the pregnancy.
During those very first two weeks, a woman’s physique prepares for ovulation and an egg is released at about day 14 of the menstrual cycle. The egg is after that swept in to the funnel-enjoy end of among the fallopian tubes, the usual site for fertilization.
If the egg is fertilized by a sperm, after that around 3 weeks after the very first day of a woman’s last period, the fertilized egg (zygote) is moved gradually along the fallopian tube to the uterus, by tiny cilia that line the tube.
The cells of the zygote divide repeatedly as it moves along the fallopian tube and the zygote takes in between 3 and five days to enter the uterus.
Once inside the uterus, cell division continues and ultimately forms a hollow ball of cells called a blastocyst. This blastocyst burrows in to the uterus wall (implantation) and develops in to an embryo.
Week 4
In weeks 4 to 5, the embryo begins to grow and develop, along with the inner cells beginning to type two then 3 layers. An inner layer called the endoderm is formed, which goes on to come to be the baby’s breathing and digestive system.
A middle layer, called the mesoderm comes to be the bones, muscles, heart and blood vessels and an outer layer called the ectoderm develops in to the mind and nervous system. Throughout these early weeks, a tiny yolk sac supplies the embryo along with nourishment until the placenta fully forms a couple of weeks later and takes over the role of providing nourishment and oxygen.
Week 5
It is Throughout this week of pregnancy that a woman misses her period. At this point, the embryo is concerning 2mm long and is currently creating a nervous system. As the ectoderm develops, a layer of cells begin to fold to type the neural tube that later comes to be the mind and spinal cord.
Another tube-enjoy structure that will certainly come to be the heart likewise begins to type and some blood vessels are currently present. Several of these blood vessels link the baby to the mother and ultimately type the umbilical cord.
Week 6
During the sixth week, the baby’s growth is rapid, along with the neural tube beginning to close and the heart beginning to pump blood. At this stage, a heartbeat can easily sometimes be seen on an ultrasound scan.
The straightforward features of the face begin to come to be apparent including canals that will certainly type the inner ear and arches that will certainly comprise section of the jaw.
There are likewise thickened spots where the eyes will certainly form. The physique begins to come to be curved shaped and small limb buds come to be visible that will certainly make in to the legs and arms.
A bump forms at the end of the neural tube which will certainly make in to the mind and head.
Week 7
By week 7, the embryo measures about 10mm and the brain, head and face begin to make rapidly. Nerve cells undergo continued progression as the mind and spinal cord start to take shape. The forehead is big and the lenses of the eyes begin to form.
The inner ear likewise begins to make and the arm buds lengthen and come to be paddle shaped. These will certainly ultimately make in to hands.
Week 8
By week 8, the baby is called a fetus. The legs type cartilage and improve in length, despite the fact that leg portions such as the knees, thigh and toes are not yet distinct. Fingers have actually started to form, the ears have actually started to come to be shell shaped and the eyes are visible.
The fetus is still contained within the amniotic sac and obtains nutrients from the yolk sac, yet the placenta continues to make and forms structures that will certainly permit it to come to be attached to the womb. The fetus might now be about 11 to 14mm in length.
The mother’s body
A pregnant woman will certainly probably not see any type of signs of pregnancy Throughout the very first four weeks. The very first authorize a woman typically notices is that she has actually missed her period. By the eighth week of pregnancy, a woman will certainly have actually missed Yet another period, despite the fact that some women experience a small quantity of bleeding Throughout the early weeks, called implantation bleeding.
By the seventh or eighth week, the womb is around the dimension of a lemon, the breasts could be tender and there could be a have to urinate much more frequently. Women might likewise feel much more tired compared to usual and begin to experience sensations of nausea or morning sickness.
Reviewed by Yolanda Smith, BPharm