The first trimester of your pregnancy begins from the first day of your last menstrual cycle and lasts till the last day of 12th week. It means that the first 3 months of pregnancy are considered first trimester. A lot of activity is going on in your body. From the fertilization of egg to the development of organs, many crucial milestones of baby’s development are achieved during this trimester. First of all, the fertilized cell divides into a cluster of cells called blastocyst and is implanted into the uterine wall where it continues developing. Development occurs most rapidly during the first trimester.
Here is a thorough guide on what to expect during your first trimester.
Week 1 to 4:You get pregnant somewhere in the middle of these 4 weeks. However, you are still considered 4 weeks pregnant even though the egg may have implanted in your uterus only 2 weeks ago. During the 4th week, your baby is only the size of a poppy seed measuring only 2mm . Even though the size is small, several biochemical changes are occurring. The cells are constantly dividing and layering up. This cluster of cells will eventually give rise to different parts and organs of your baby.
Your baby’s tiny heart and nervous system has already started developing at this stage. Surprisingly, the little dot growing inside you has already developed some of its own blood vessels, connected to you via a tiny cord that will eventually develop into an elaborate umbilical cord. At this stage, your baby is known as an embryo. At this stage, your baby gets all its nutrition from the yolk sac and it continues until the placenta is developed. The embryo is also surrounded by amniotic fluid in the amniotic sac which provides protection and acts as a shock absorber. You may have already started feeling symptoms of pregnancy at this stage such as nausea, spotting, tender breasts and abdominal discomfort.
Week 5 to 8:By week 5, the tiny dot growing inside you starts taking shape. Your baby’s tiny nose and eyes start to form. By this time, your baby is sized at 9mm, about as big as a fingernail. Your baby’s hands and feet start to appear as little buds. The skull bones form around their tiny brain. The outer layer of amniotic sac develops into an elaborate placenta. Placental cells divide and penetrate into the uterine wall, maintaining a blood supply for the baby with maternal blood vessels serving as a source. Placenta will now serve as a source of nutrition for the baby. You also start having cravings around this time or may suddenly end up despising something you previously loved to devour. It is very important to take proper care of your nutrition for yourself and your baby. Having early pregnancy symptoms and cravings is normal at this time.
During the 6th week, your baby resembles a tadpole with a tiny tail and curved back. Your baby’s heart started beating sometime during the 4th week and a bulge can be seen at the place where the heart will eventually fully develop. Even at this early stage, the heartbeat can be detected using a transvaginal scan. Just like heart, there is a bump at one end that will eventually develop into your baby’s head. The primitive facial features can be made out at this stage. Your baby is covered by a thin layer of skin. Cravings, headaches and nausea/vomiting may become pronounced at this stage.
During the 7th week, your baby becomes as big as the size of a grape. Your baby appears more like an alien at this stage as their head develops faster than the rest of the body. The tiny buds of their hands and feet start taking shape and cartilage starts to develop that will eventually turn into solid bones. As the nervous system further develops, a network of nerves is laid down throughout the body. They start showing little movements at this stage as signals start to travel down brain and spinal cord to the muscles. Soon enough, your tiny miracle will be able to start feeling certain sensations such as temperature and taste. You may feel more thirty with frequent urge to urinate during this time.
During the 8th week, your baby doubles in size and start to look like a tiny human. Their legs and arms are differentiated and their arms are longer than their legs as at this stage, the upper body is growing faster than the lower body. Amniotic sac is well developed, keeping your baby safe. Placenta further develops forming chorionic villi that burrow into the uterine wall, establishing a proper blood supply. By the 8th week, your baby is referred to as a fetus rather than embryo. Make sure to make an appointment and visit your doctor.
Week 9 to 12:At 9th week, your baby measures 22mm, as big as a strawberry. By this time, pigment starts to appear in their tiny eyes and eyelids start to take shape. Taste buds start to appear on the tongue. By this time, the genitals of your baby also start to develop. A tiny bud of cells appears between the legs that will eventually give rise to a penis or clitoris. Your baby has already started moving in the womb but it may take some time for you before you start to feel it. Hormonal surge can make you feel very emotional with frequent mood swings.
At 10th week, your baby measures about 3cm. if you could look at their tiny face, you would be able to spot their nostrils and upper lip. Your baby has developed the ability to react to light by this time. The eyelids develop further as well as jaw bone starts taking shape complete with all their milk teeth. An ultrasound scan at this stage will be able to spot the movements of your baby. Indigestion and heartburn start around this time and may continue throughout the course of pregnancy. You may also feel faint and dizzy.
At 11th week, your baby starts looking more like a baby. Soon, your baby bump will start showing. If you could look at your baby, you would be able to spot their teeny tiny fingers and toes as they start to separate from each other. Your baby’s eyes are now well developed and completely covered with the eyelids. Their kidneys have started filtering blood and their stomach has started making gastric juice.
At 12th week, all the organs of your baby appear well developed. The organs, limbs, muscles, bones, vessels etc. are all in their place and only need to develop further and grow bigger in size. At this stage, your baby is fully formed, though still the size of a plum. Placenta is fully developed, and the cartilaginous network in their muscles is starting to transform into the hard bone. Your baby is capable of moving, waving, dancing, swallowing; you just cannot notice it as yet. From now onwards, your baby will continue to grow and grow until fully developed. Some women may experience excessive salivation and nosebleeds.