What to Expect During the First Trimester

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Pregnancy consists of three trimesters. Each trimester is responsible for different growing functions of your baby and lasts about 13 weeks each. A full-term pregnancy lasts for 40 weeks. It is normal for you to experience each trimester differently. The first 13 weeks of pregnancy are considered the first trimester. This is when you will experience the first signs of pregnancy such as morning sickness and tender breasts. By the end of the 13 weeks, the organs of the foetus will start to develop. 

The gestational age of your pregnancy is known as the first day of your last period. Your healthcare provider will calculate your due date by adding 40 weeks from the first day of your last period. Most women only realise they are pregnant from 4 weeks, and some even later than that. 

The Beginning of Pregnancy Explained

The first two weeks of your menstrual cycle count as your first two weeks of pregnancy. The first week is known as your period and the second week is your period. Once ovulation occurs, egg cells travel through the fallopian tube to the uterus waiting for a sperm cell to start fertilisation. Once fertilisation occurs in the fallopian tube it will travel to the uterus, this is called week 3 of your pregnancy. Once the fertilised egg reaches your uterus it will implant into the uterus lining. This will alert your body that you are pregnant and start the process of changing your body and hormones. 


Your Experience During Week 5 

During fertilisation, your baby is the size of a headpin (+- 0.1-0.2 mm). After the fertilised egg is implanted in the uterus, your body will produce a hormone called human chorionic gonadotropin (hCG). This hormone is what will turn your pregnancy test into a positive one. During week 5 of your pregnancy, the baby will only be 3 weeks old and is the size of +- 1-4mm. During this time you will experience a missed period, followed by implantation bleeding (spotting). You might already experience nausea during this time. 

The Baby’s Growth During Week 5

The embryo will develop into three layers (gastrulation), the outer layer is called the ectoderm, the middle layer is called the mesoderm, and the inner layer is called the endoderm. These layers will start the process of developing tissue and organs for the baby. You will be able to see a head and tail during this time. 


Your Experience During Week 6

During this time, you will experience breast tenderness and see that your nipples are darker. This is because of the blood supply that is moving to your breasts. You may also experience a change in your smell and feel tired. You can have your first ultrasound this week. 

Your Baby’s Growth During Week 6

Your baby’s size will now be 4-10 mm The brain and spinal cord will start to develop, followed by the baby’s jaw. Your baby will start developing arms and their heart will start to pump blood. 


Your Experience During Week 7

You will experience food cravings, your pre-natal supplement might cause nausea, it is advised that you take them with food. Your vulva and vagina will start to turn purple, this is because of the increased blood supply to these areas. 

Your Baby’s Growth During Week 7

Your baby’s size will now be 11-15 mm. Your baby is vulnerable during this stage as all the essential organs start to develop.  The spinal nerves will now begin to grow. The head will appear much larger than the rest of the baby’s body. Your baby’s eye lenses will start to form, and ears will start to appear. This is also the stage of forming the basic digestive tract and hands. Your baby’s jaw, lungs, nose, and palate will start to develop now. 


Your Experience During Week 8

You might experience severe nausea during this time. Your blood flow will increase leading to more fluid build up and urinating. 

Your Baby’s Growth During Week 8 

Your baby’s size is +-16 mm. The baby’s head will still appear bumpy, the eyes will become more obvious, the nose, lips, and tongue will be formed, and taste buds will begin to develop. Your baby will start developing internal sex organs, followed by arms, legs, and fingers. 


Your Experience During Week 9

Your uterus will now be double in size, and you might not fit into your clothes anymore. 

Your Baby’s Growth During Week 9

Your baby’s size will be +-23 mm. Eyelids will begin appearing, the upper limbs will start to lengthen, and nipples and first hair follicles will form. Taste buds will continue to develop as well as tooth buds. The heart will divide into two chambers and the tail will disappear during this week. 


Your Experience During Week 10

Your waist will start growing this week, so it will be a good time to invest in maternity pants. You might also experience mood changes caused by hormones. 

Your Baby’s Growth During Week 10

Your baby’s size will be 31 mm. The head will be rounder, the eyelids will be more developed and might close at the end of this week. Ear, upper limbs, and toes are more developed. The toes will be separated by the end of this week. Your baby might start moving during this week. 

Your Experience During Week 11

Due to extra blood supply, your temperature might be higher. You will start to notice a change in your weight. For some women, the nausea of the first weeks will start to fade. During this week you can have an ultrasound and test for chromosomal abnormalities such as Down syndrome.

Your Baby’s Growth During Week 11

Your baby’s size will be 41mm. Your baby’s organs will continue to grow and develop. The head will be more rounded, and the eyelids will start to close. The nose and ears will take shape. Your baby’s urine formation will begin, and external genitals will start to develop. 


Your Experience During Week 12

Changes in your hormones might result in headaches. You might experience dizziness due to blood pressure changes.

Your Baby’s Growth During Week 12

Your baby will start developing a vocal cord, and fingernails. Your placenta will take over hormone production to sustain the pregnancy. Your baby will receive oxygen from your blood supply through the umbilical cord and placenta. 

By week 13 you will enter the second trimester of your pregnancy.

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