Pregnancy is a 9-month period where both mom and fetus change dramatically. Each 3-month period is known as a trimester, and each trimester is associated with different milestones for both the fetus and the mother.
The First Trimester (0–3 Months)
The first trimester spans the initial 12 weeks of a woman’s pregnancy. During this period of time, the embryo changes into a fetus with fingers, organs and a heartbeat. There is a wide range of changes and symptoms that mothers experience during the first trimester. To accommodate these physical changes, moms can make many lifestyle modifications can be made with regards to sleep, nutrition, exercises, and supports.
Weeks 0–2
The beginning of a pregnancy can be calculated by determining the first day of your last menstrual period. After 10–14 days, a female will release an egg that combines with sperm from a male resulting in conception. During the first 2 weeks, pregnancy is extremely difficult to detect, and you may not test positive on a pregnancy test.
Week 3
During the third week, the fertilized egg will divide and reach the size of a vanilla bean seed. You of the most noticeable bodily changes will be an increase in the production of hormones such as estrogen, progesterone, and human chorionic gonadotropin (hCG). Some women may experience heightened senses or mild symptoms such as lower abdominal pressure and a metallic taste on their tongue. Starting this week, you may want to increase your iron, protein, and vitamin C levels by incorporating fruits, vegetables, meat, and nut products into your diet.
Week 4
The fourth week of pregnancy signals successful fertilization. The fertilized egg will implant onto the wall of the uterus, and the embryo. Half of the embryo will grow into the fetus while the other half will form the placenta. The placenta is responsible for transporting nutrients to the growing embryo, which is now the size of a poppy seed. Increased hormone levels and a spongy uterine wall create the perfect environment for development. Most women are unaware of their pregnancy until the 4–6-week mark. Early symptoms of pregnancy include a missed period, stubborn urge to urinate, sensitive breasts, fatigue, and mood swings. It is important to avoid hazards, limit caffeine intake, and stop the consumption of alcohol, cigarettes, and other drugs.
Week 5
Many amazing things occur during the fifth week of pregnancy. The first organ system, the circulatory system, will begin to form. The tube eventually forms a functional heart begins to pump, although you may not be able to hear a steady heartbeat for another few weeks. During the first few months of pregnancy, you may experience fatigue and an increased need for sleep. These symptoms may be accompanied by nausea, vomiting, food cravings, and excess saliva. It is imperative to get enough sleep during the first trimester and form a structured sleep schedule with napping and an early bedtime. Most women are recommended to take prenatal vitamins (folic acid, vitamin B12, etc.), eat a balanced diet, and reduce the frequency of physically demanding tasks.
Week 6
Your baby will begin to develop a liver, facial features, limbs, and a pair of lungs. At the size of a sweet pea, the embryo takes on a fetal position in the womb. At 6 weeks, an at-home urine test will likely test positive due to the increased levels of hCG. Although referred to as “morning sickness”, certain smells and tastes can trigger vomiting and nausea throughout the entire day. To help with nausea, you can avoid spicy and greasy foods and eat smaller portions more frequently throughout the day. Women may experience breast changes including enlarged breasts, nipple sensitivity, and changes in areola colour and texture.
Week 7
Your baby is now as large as a blueberry and has started to develop webbed hands and feet stubs. Don’t worry, it’s perfectly normal! Brain development and kidney size have changed a lot at this stage. Hormonal changes can cause acne breakouts on your face and/or body. Consulting a dermatologist about medications and washing your face with gentle cleansers can help eliminate some of the skin problems that may arise at this stage. Food cravings are normal, but it is important to find a balance between giving in and maintaining a balanced diet. Food aversions are also common and can be improved by eating bland food substitutes.
Week 8
Your baby is beginning to form facial touch receptors, a nose, lips, and sense of taste. In terms of size, your baby spans the length of a raspberry. The development of the intestines, retina, and kidneys are well underway by the end of the first two months. If you have not already, it is important to visit your physician. Healthcare professionals will conduct tests during your first appointment such as collecting a urine sample, measuring blood pressure and weight, doing a pap smear, blood tests and a pelvic exam. Symptoms that have been present since the 3-week period may continue in addition to bloating, vaginal discharge, and constipation.
Week 9
As your child develops, their head will straighten out, their ears will continue to grow, and limb movement will also take place. As large as a green olive, your baby’s heartbeat will continue to grow stronger and may be detected on an ultrasound. Heightened emotions can be a result of hormonal changes and can lead to random laughter and crying. Although mood fluctuations are expected, persistent feelings of low mood or anxiety may be a concern and something to report to your healthcare professional. If you notice such negative feelings, please take a look at MomsOverMatter — our free mental health resource for pregnant women and mothers in the postpartum period. Intense feelings of fatigue are also anticipated as a result of increased energy demands. Many physicians will recommend a genetic test using the non-invasive prenatal testing (NIPT) tool if there is a family history of certain disorders.
Week 10
Your prune-sized fetus now has distinct fingers and toes; at this stage in the pregnancy, their bone and cartilage continue to form. At this point, some women may notice a slight bump at the bottom of their abdomen, but it is completely normal if you do not. Visible veins on your breasts and abdomen can be a consequence of the expanding blood supply that is required to nourish your growing baby. Faintness, dizziness, and occasional headaches are common for many women and can be alleviated using acetaminophen instead of aspirin or ibuprofen.
Week 11
The fetus will develop hair follicles on their head, and nail beds for their fingers and toes. Comparable to the size of a large strawberry, your fetus will now have distinct features such as ears and a tongue. Weight gain is a common concern for women during pregnancy; however, most women only gain an average of 4–5 pounds during the first trimester. Genetic and external factors will determine how much weight you may gain. It is advised to consume an extra 300–500 calories of highly nutritious food at this stage. Women may have weaker immune systems during their pregnancy, so it is important to wash your hands, social distance, and vaccinate against certain illnesses as advised by a healthcare professional.
Week 12
The digestive system, muscles, and vocal cords develop, and your fetus will increase white blood cell production to fight infections after birth. Most of the major organ systems started to form, and the pituitary gland has started producing sex hormones. If you have not heard the baby’s heartbeat yet, you should be able to hear it at your next doctor’s visit. Your child is as big as a lime and the placenta will now produce the hormones necessary to support your child. You may experience less peeing as your abdomen becomes larger and rounder. Many women face occasional headaches, and this symptom can be worse for those that have a history of migraines. To combat low blood pressure and low blood sugar, it is important to stay hydrated and continue eating a balanced diet.
The Second Trimester (3–6 Months)
The second trimester of pregnancy is between months 3–6, where both the mother’s and fetus’s body continue to grow. Your fetus will be between 13 and 16 inches long, and weigh about 2 to 3 pounds by the end of the second trimester. Morning sickness is relatively rare during the second trimester, and extreme tiredness and breast pain will ease due to the decrease in hormone levels. Whereas diet in the first trimester was important for development and differentiation of the fetus’ organs, diet in the second trimester is important for brain development and overall fetal growth.
Week 13
By week 13, the baby’s bones begin to form and develop. A full heart exam of the fetus can be performed since both the aorta and pulmonary trunk (two structures of the heart) have developed and are visible. This is an important stage in pregnancy as heart defects are the most frequently encountered congenital malformation.
Week 14
As early as week 14, your fetus is developing coordination with their facial muscles. These same muscles will be used to smile, laugh and cry. The fetus is still relatively small: only the size of a ripe lemon. Blood samples as early as week 14 can be used to diagnose anemia, zinc, and vitamin B deficiency. At this time, the baby’s fingernails and toenails are beginning to form.
Week 15
By week 15, your energy may be growing due to hormonal changes. The bones that were developing in the fetus earlier on are beginning to harden. This is the time when the fetus will begin developing eyebrows and eyelashes made of very thin hair.
Week 16
The first 16 weeks of pregnancy have been cited as the most critical period in human development. The fetus’ circulatory system has finished developing by this week. The fetus’ eyes are still glued shut, but they will be able to start perceiving some light that shines through your belly. Additionally, 16 weeks is typically when you will be able to feel your baby’s first kick.
Week 17
By week 17, the fetus begins developing fat which is important for protecting their bones and organ systems. Additionally, the umbilical cord connecting you to your baby is strengthening and thickening for optimal delivery of nutrients and other things that your baby needs to grow. This also means it’s important for you to watch what you consume and be careful not to smoke or drink excessively.
Week 18
Your baby will be able to hear their first sounds by week 18. Although they can detect sounds, their hearing capacity is not yet perfect. Week 18 is also the time when the placenta becomes a fully developed fetus.
Week 19
The vernix caseosa is a white, creamy biofilm that begins to show up at week 19 of pregnancy and continues to thicken throughout the coming weeks. Its purpose is to protect the delicate fetal skin; it serves as a barrier to water loss, temperature regulation, and protection from infections. Week 19 is also when the main airways in the lungs form to prepare your baby for taking their first breath.
Week 20
Week 20 marks the halfway point of a typical pregnancy with the fetus being about the length of a banana. At this point, the placenta is fully developed for nutrient and waste transport.
Week 21
At week 21, your baby may aggressively kick. Relaxin, a hormone, will release to help to lessen the pain and discomfort of such kicks. This hormone also relaxes the uterine muscles to allow the uterus to stretch when it is time for birth. Week 21 is when the fetus’ rapid eye movements (REM) begin during sleep.
Week 22
Week 22 is when your baby begins growing their first bodily hair. This hair will typically fall out within the first few weeks after birth but is used to protect the baby. Your baby can fully open and close their fist by the end of week 22.
Week 23
By week 23, your baby is around a foot long. REM sleep increases at this stage to help brain development and strengthen brain structures (Okawa et al. 2017). Week 23 is when we can identify ridges forming on the fingertips and feet of your baby via medical imaging.
Week 24
At week 24, your baby’s movements will be so strong that others can put their hands on your torso and feel their kicks. Your baby is developing muscle tone to assist in kicking and movement. Week 24 also marks the time when your baby’s inner ear is fully developed. This means that your baby can hear sounds and words but will not understand the language you are speaking.
The Third Trimester (6–9 Months)
The third trimester occurs from week 28 to week 40 of your pregnancy. During this time, several changes will occur to you and your fetus to prepare for delivery. Your baby will be gaining much more weight and you may start to experience false labor contractions. You may experience swelling in the feet and ankles and shortness of breath due to your baby pushing on your diaphragm. It is important to visit your doctor regularly to ensure there are no complications with the birth of your baby.
Week 26
At this time, you will be able to feel your baby move. You may need to purchase a body pillow to help you sleep better since you may experience many disturbances at night, from your baby twisting and turning. By the 26th week of your pregnancy, your baby is approximately 2 pounds and 9 inches long.
Week 28
Your baby will be about 10 inches long by week 28. Additionally, your baby’s eyelids have now formed, and their eyes are partially open. The baby’s brain will be able to control their body temperature and breathing movements.
Week 30
During this week, the fetus will have lungs that are functional and can breathe in air. Red blood cells will start to form in your baby’s bone marrow. Your baby may have a full head of hair now! Although you may not be able to see it, your baby is able to suck its thumb and cry.
Week 32
At this point in your pregnancy, your baby has developed toenails. The baby’s lanugo (soft hair that covers the skin) will begin to start falling off. Your baby will be around 11 inches long and their intestinal tract will start absorbing important minerals such as iron and calcium.
Week 33
Your baby will now be able to detect light and other stimuli. The baby’s bones will also be hardening, while the skull remains soft to allow for childbirth.
Week 34
At this point, your baby has pink and smooth skin, and their fingernails have now reached their fingertips. Almost all babies that are delivered at this point in the pregnancy will live if intensive care services are available.
Week 36
Your baby is now much plumper and larger. Although your child will have limited movement due to their size, they will still be able to roll around.
Week 38
Your baby can now grasp firmly and will start moving so that they are in a head-down position. However, your baby fails to move properly during this time, a breach pregnancy could occur where your baby exits the womb from the rear instead of their head. The circumference of the baby’s head and abdomen will be equal at this period.
Week 39
Your body will start to prepare for the delivery of your baby by allowing the baby to fall into your pelvis. The doctor will be able to assess the size of your baby by measuring your belly during this time.
Week 40
Your baby is now around 14 inches in length. They are considered to be full-term, and birth typically occurs either two weeks before or after the expected due date, which is determined by your doctor. If the baby remains in the uterus for more than two weeks after the predicted due date, your doctor may talk to you about inducing your labour.
Although there will be many changes that occur to the baby during this time, it is important that you are aware of the symptoms and physical changes you will experience as well. Firstly, you may experience more heartburn and shortness of breath since the baby will be putting pressure on your diaphragm. Additionally, you may notice more swelling in your feet and ankles, which is due to increased blood pressure. This increase in swelling can also be due to higher blood volume levels which are directly caused by weight gain. Another potential complication of increased blood volume is varicose veins which are likely to become worse during this period.
Authors
Radha Sharma, Rebecca Ladouceur, Pegi Kaimi, and Mateusz Faltyn
lleTTonna
lleTTonna is a Canadian organization whose mission is to help mothers and their families thrive throughout pregnancy and the postpartum period via the development of innovative and personalized mental healthcare technologies.
Designed in consultation with physicians, psychologists, nurses, social workers, and women who have recovered from postpartum depression and anxiety, MomsOverMatter is a free web application that delivers information regarding personalized treatment options for postpartum depression and related disorders based on user-generated responses to validated questionnaires.
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*Disclaimer: The content in this article is for informational purposes only and does not represent any form of formal diagnosis or medical recommendation. Only a trained healthcare professional can make diagnoses or recommendations. If you are concerned, please consult your healthcare professional
