Chinese Medicine

How to Track Pregnancy? A 40-Week Pregnancy Change Guide

Author Bowtie Team

Updated on 2025-07-25

Disclaimer: This article is translated with the assistance of AI.

Expecting a baby? As a first-time mom, you’re likely both thrilled and nervous. Curious about the changes in your body and your baby’s growth over 40 weeks? The Bowtie team breaks it all down for you in this detailed guide!

How to Calculate Pregnancy Weeks & Due Date

When it comes to calculating pregnancy weeks or due dates for natural conception, there are two main methods. If your menstrual cycle is very regular, your ovulation timing will likely be quite accurate, so you can calculate based on the conception date. The other method is based on your menstrual cycle. For assisted reproduction, calculating pregnancy weeks or due dates is often easier since the date of embryo implantation or ovulation is known, making the results more precise. Keep in mind that these calculations might slightly differ from the actual due date, so it’s best to consult a doctor for the most accurate estimation.

	Calculation Method
Based on Menstrual Cycle (Natural Pregnancy)	Since pregnancy typically lasts about 40 weeks (or roughly 38 weeks from conception), you can count 40 weeks or 280 days from the first day of your last menstrual period. Use the “add 7, subtract 3” method: Add 7 days to the first day of your last period and subtract 3 months. For example, if your last period started on April 11, subtract 3 months (April – 3 = January) and add 7 days (11 + 7 = 18). Your due date would be January 18.
Based on Conception Date (Natural Pregnancy)	If you’re sure intercourse occurred during ovulation, add 266 days or 38 weeks to that date to estimate your pregnancy duration and due date.
IVF: Based on Implantation Date (Assisted Reproduction)	Add 38 weeks (266 days) to the date of egg fertilization to determine the due date. Alternatively, add 38 weeks to the fertilization date, then subtract the number of days until embryo implantation. For instance, if the embryo was implanted on day 3, subtract 3 days.

Pregnancy Week 1: What to Expect

During the first week of pregnancy, since it’s the very early stage, most women won’t notice any signs or changes indicating they’re pregnant.

Throughout pregnancy, both the mother and baby undergo various changes at different stages. If you’re soon-to-be a mom, check out the table below to get a glimpse of what happens to both you and your baby across different weeks and trimesters.

Early Pregnancy: Weeks 2-12 Changes

Week	Mother’s Body Changes	Baby’s Development	Dietary Restrictions
Week 2	An egg is released from the ovary and swept into the fallopian tube. Within the next 12 to 24 hours, one of your partner’s roughly 250 million sperm will swim up and fertilize it, forming a zygote. At this stage, the baby’s gender is determined: a Y chromosome means a boy, while an X chromosome means a girl. You might experience intermittent sudden lower abdominal pain, breast swelling, elevated body temperature, or increased vaginal discharge.	No noticeable changes yet.	Stop smoking or drinking alcohol. Avoid over-the-counter medications and consult a doctor before taking any drugs. Take a daily multivitamin with at least 400 mcg of folic acid to reduce the risk of birth defects.
Week 3	The fertilized egg implants in the uterus and begins to grow. You might experience light spotting, breast swelling, pain, or tingling, with heightened sensitivity to touch due to increased blood flow, estrogen, and progesterone levels.	The baby starts forming, though no significant changes are visible yet.	Opt for foods rich in folic acid like beans, bread, and cereals, or take folic acid supplements directly.
Week 4	A pregnancy test can now confirm you’re pregnant. Pregnancy slows digestion, allowing bacteria in the gut to linger, ferment, and produce gas, leading to bloating. You may also feel tired, moody, or constipated.	All of the baby’s organs begin to develop and function. The forming baby now has two cell layers (ectoderm and endoderm), and the maturing placenta starts working to supply oxygen and nutrients for growth. The amniotic sac, which provides cushioning, and the yolk sac, which produces red blood cells for the baby, are also ready.	Cut back on gas-causing foods like beans, cauliflower, broccoli, asparagus, onions, pears, and carbonated drinks. Eat smaller, more frequent meals and chew slowly. Drink from a glass instead of a bottle or straw, and avoid gulping beverages.
Week 5	You may feel tired, moody, and experience breast swelling. Nausea and frequent urination are common.	The baby’s brain begins to develop at this stage. The baby now consists of three cell layers: ectoderm, mesoderm, and endoderm. The ectoderm will form skin, hair, nails, tooth enamel, mammary glands, and sweat glands; the mesoderm develops into muscles, cartilage, bones, and subcutaneous tissue; and the endoderm forms lungs, intestines, the basic urinary system, thyroid, liver, and pancreas. The primitive placenta and umbilical cord start functioning.	Avoid diuretic drinks like coffee, tea, and other caffeinated beverages.
Week 6	Hormonal changes may cause mood swings. Light vaginal bleeding may occur. Your sense of smell becomes sharper, often leading to nausea (especially in the morning).	The baby is about the size of a lentil (4 to 5 mm wide). The heart starts beating and develops into left and right ventricles. Eyes, nostrils, ears, limbs, intestines, and lungs are forming. The tongue and vocal cords begin to take shape.	Eat smaller, frequent meals. Avoid foods with strong odors. Try sour plums or ginger to ease nausea.
Week 7	Some women experience vomiting due to morning sickness. As the embryo grows, it presses on the bladder, causing frequent urination.	The baby is about half an inch long, with elbow joints and distinct, slightly webbed fingers and toes. Teeth, the inside of the mouth, ears, eyes, and nasal wings are forming. The baby’s liver starts producing red blood cells at this stage.	Keep simple snacks like soda crackers handy. Eat small, frequent meals or snacks to avoid an empty stomach. Avoid greasy, spicy, or acidic foods.
Week 8	Symptoms include frequent urination, nausea, breast tenderness, fatigue, mood swings, and bloating. A less common symptom is increased saliva production.	The baby’s hands bend at the wrist, and knee and elbow joints are formed.	Eat more fruits, vegetables, dairy, whole grains, and lean meats.
Week 9	Early pregnancy progesterone relaxes smooth muscle tissues, including the gastrointestinal tract, leading to bloating, slower digestion, more gas, and burping.	The baby’s basic physiological structures are in place. Eyelids fully cover the eyes and are tightly shut, earlobes are present, and the mouth, nose, and nostrils are clearly visible. The baby can move its limbs.	Avoid chewing gum or soft candies. Eat smaller meals and drink less liquid while eating. Sit while eating and chew slowly.
Week 10	Breasts and abdomen start to protrude. The rapid growth of the uterus stretches the supporting ligaments, causing abdominal pain. Saliva production increases more than usual.	Vital organs—liver, kidneys, intestines, brain, and lungs—are in place and starting to function. Fingernails, toenails, and fetal hair begin to grow.	Eat smaller, frequent meals. Drink plenty of water and carry a bottle for easy access. Suck on hard candy or chew sugar-free gum.
Week 11	You may notice clear vaginal discharge.	With the development of the diaphragm, the baby can hiccup. Fingers and toes are now separated.	Continue taking prenatal vitamins daily. Opt for calcium-free prenatal vitamins if needed.
Week 12	Your waistline thickens, and you may experience heartburn.	The kidneys start functioning and produce urine into the bladder. The baby can make reflex movements, including sucking.	Eat smaller meals and chew thoroughly. Avoid fried, spicy, greasy, or acidic foods. Skip chocolate. Avoid soda or caffeinated drinks, and reduce water intake between meals. Wait at least an hour after meals before lying down.

Pregnancy Weeks 13-27: Second Trimester Guide

Week	Changes in Mom’s Body	Baby’s Development	Dietary Restrictions
Week 13	Hormonal changes and increased blood supply to the baby may reduce blood flow to the mom, causing dizziness. Breasts start producing colostrum. Appetite increases, along with heightened libido and renewed energy.	Baby’s unique fingerprints are formed. Kidneys and urinary tract start functioning, expelling swallowed amniotic fluid as urine.	With a better appetite, focus on nutritious foods.
Week 14	Nausea, fatigue, and breast tenderness begin to subside.	All basic structures of the baby (internal and external) are formed. Baby starts growing fine, soft body hair called lanugo, covering the entire body. Liver begins producing bile, and spleen starts making red blood cells. Baby starts producing urine, releasing it into the amniotic fluid.	Focus on nutritious foods.
Week 15	Increased estrogen levels may cause swollen mucous membranes, leading to nasal congestion. Some moms may experience nosebleeds due to increased blood flow and dilated nasal blood vessels.	Baby’s taste buds and lung air sacs begin to form. Baby can sense light. Baby can move all joints and limbs.	Drink plenty of water.
Week 16	You might start feeling “baby kicks.” Increased blood flow to skin vessels gives a rosy complexion. Pigmentation darkens around nipples, thighs, and underarms.	Baby’s weight doubles, and length increases by several inches. Circulatory system and urinary tract start functioning. Eyes can move slowly, and toenails begin to grow.	No special precautions.
Week 17	Backache and lower back pain. Memory may be worse than before pregnancy.	Baby’s skeleton starts hardening into bone. Umbilical cord grows stronger and thicker.	No special precautions.
Week 18	Appetite increases significantly.	Baby’s reproductive organs are formed, including uterus, fallopian tubes, or penis.	Avoid drinking water a few hours before bed to reduce nighttime bathroom trips. Keep snacks by the bed for midnight hunger pangs.
Week 19	Lower abdominal pain or sharp, sudden pain on one or both sides. Skin pigmentation darkens in various areas. Indigestion may cause a “heartburn” sensation. Constipation.	Kidneys continue producing urine, and scalp hair starts growing. This stage is crucial for sensory development: brain areas for smell, taste, hearing, vision, and touch are forming.	Drink plenty of water and eat fruits and veggies for smoother digestion. Eat small, frequent meals. Avoid irritants like spicy, greasy, or acidic foods.
Week 20	Swelling in hands and feet. Dry eyes. Lower leg pain or cramps. Mild gum bleeding.	Baby swallows more often and starts producing meconium, which accumulates in the intestines.	Ensure adequate iron intake from red meat, poultry, fish, lentils, other legumes, and spinach.
Week 21	As the baby grows, increased pressure in the abdomen may cause back pain, abdominal pain, or shortness of breath. Pregnancy adds pressure to the legs, making varicose veins more likely. Hormonal changes and increased facial oil production may lead to acne.	Baby’s eyebrows and eyelids are fully developed. If it’s a girl, her vagina is formed at this stage.	Avoid fried or irritating foods to prevent acne.
Week 22	Belly expands to accommodate the growing baby, possibly leading to stretch marks and itchy skin. Darkened pigmentation appears on the belly, buttocks, thighs, hips, and breasts. Elevated estrogen levels may cause spider veins—small, red, branching lines—on the face, neck, upper chest, and arms.	Eyes are developed, though iris pigment hasn’t formed yet. Lips become more defined, and the first signs of teeth appear as tooth buds form under the gums. Baby’s lips become more prominent.	No special precautions.
Week 23	Pregnancy-induced “innie” belly button may flatten and soon protrude. Mild swelling, especially in ankles and feet.	Blood vessels in the lungs are developing for future breathing. At this stage, baby’s skin is red and wrinkled, often appearing pink or reddish at birth.	Drink plenty of water to stay hydrated and prevent swelling.
Week 24	Stretching skin on the abdomen and chest may feel itchy. Some moms experience “dry eye syndrome,” a common pregnancy symptom, with eyes feeling gritty, dry, and sensitive to light. Check out more on Dry Eye Syndrome . Increased body size may lead to snoring during sleep. Hands may feel tingly at times.	Brain grows rapidly, and taste buds start functioning. Lungs develop bronchi and cells that produce surfactant (a substance helping air sacs inflate). Baby becomes more sensitive to sounds at this stage.	No special precautions.
Week 25	Fingers and wrists may feel tingly, numb, or swollen, with some experiencing “Carpal Tunnel Syndrome.” Learn more about Carpal Tunnel Syndrome . Hair appears thicker and shinier than ever, while body hair may grow darker and denser. Due to androgen influence, new hair may grow on the chin, upper lip, jaw, cheeks, chest, or belly.	Baby’s hair color and texture become noticeable, though they may change after birth.	No special precautions.
Week 26	Frequent urination, swollen feet, and anxiety may affect sleep quality. Constipation.	Nerves in the baby’s ears are developing, increasing sensitivity to sounds. If it’s a boy, his testicles begin descending into the scrotum.	Drink plenty of water (6-8 glasses daily). Eat high-fiber foods like cereals, oats, fruits, and vegetables. Don’t stop taking iron supplements without consulting a doctor. Ask your doctor about fiber supplements or stool softeners.
Week 27	Symptoms like back pain, lower back pain, and posterior pelvic pain may appear. Leg muscle cramps. Enlarged uterus pressing on pelvic veins and rectum may cause swollen anal veins and difficulty with bowel movements, leading to hemorrhoids. Learn more about Hemorrhoids .	Baby can open and close eyes at this stage. Sleep patterns become more regular.	Drink plenty of water (6-8 glasses daily). Eat high-fiber foods like cereals, oats, fruits, and vegetables. Don’t stop taking iron supplements without consulting a doctor. Ask your doctor about fiber supplements or stool softeners.

Pregnancy Weeks 28-40+: What to Expect

Weeks	Changes in Mom’s Body	Baby’s Development	Dietary Restrictions
Week 28	You might experience foot discomfort, swelling, or cramps.	Baby’s eyelashes are fully developed. Baby’s fat layer is getting thicker.	Reduce caffeine and antihistamine intake to avoid worsening leg discomfort.
Week 29	As your body prepares for breastfeeding, your breasts may secrete pale yellow “colostrum.” You may feel heartburn and constipation. Pregnancy hormones like progesterone relax smooth muscles, including the digestive tract, and reduced abdominal space slows digestion, causing bloating.	Baby’s muscles and lungs are maturing, and the head grows larger with brain development. Neurons in the brain are developing.	Eat high-fiber foods and drink plenty of water (at least 8 cups daily).
Week 30	Stretch marks become more noticeable. Fatigue sets in due to insomnia and various discomforts. Mood swings, physical discomforts, and hormonal changes may lead to prenatal depression.	Baby can now distinguish between light and dark and may even follow a light source.	No special precautions needed.
Week 31	Breasts soften in preparation for breastfeeding. Uterine contractions increase, vaginal discharge changes (mucus-like, pink with blood streaks), abdominal pain or menstrual-like cramps occur, and pelvic pressure causes lower back pain.	Baby’s head can move side to side unconsciously.	No special precautions needed.
Week 32	Some may experience Braxton Hicks contractions (false labor).	Fingernails and toenails are fully grown. Some babies even have hair on their heads.	No special precautions needed.
Week 33	As baby grows rapidly, abdominal pressure increases, leading to shortness of breath, bloating, and even urinary leakage. Fingers, wrists, and hands may feel painful or numb.	Baby’s bones start to harden, but the skull remains soft and flexible with gaps to allow compression during birth through the narrow birth canal.	No special precautions needed.
Week 34	You’ll often feel baby’s movements like stretching or kicking. You may experience “supine hypotensive syndrome”: lying on your back can cause changes in heart rate and blood pressure, leading to dizziness until you change position. Itchy red bumps or stripes may appear on your belly (often evenly spread across thighs and buttocks). This harmless condition is called PUPPP (Pruritic Urticarial Papules and Plaques of Pregnancy).	Baby’s lungs are fully mature.	Drink at least 8 cups of water daily to stay hydrated; drink more if exercising or in hot weather. Eat small, frequent meals instead of three large ones to prevent blood sugar drops. Take iron supplements or prenatal vitamins with iron.
Week 35	Braxton Hicks contractions (false labor) become more frequent and regular. The uterus is now under the ribcage and has expanded to about 15 times its original size.	Baby’s liver can now process some waste or toxins.	No special precautions needed.
Week 36	As baby descends into the pelvis with the head facing down, upper abdominal pressure eases, and breathing difficulties lessen. False contractions become more frequent. About 3% to 7% of pregnant women may develop preeclampsia, with symptoms like swelling in hands and face, sudden weight gain (due to water retention), blurred vision, spots in vision, sudden severe or persistent headaches, and upper abdominal pain.	The fine hair (lanugo) and waxy coating (vernix) on baby’s body are shedding.	Opt for small, frequent meals.
Week 37	Vaginal mucus discharge increases. False contractions become more frequent and last longer.	Baby is developed enough to survive outside the womb. Some babies already have hair.	Reduce fluid intake in the afternoon or evening to avoid frequent urination disrupting sleep.
Week 38	Swelling in feet, hands, or face, persistent severe headaches, blurred vision, spots in vision, or upper abdominal pain may occur.	Baby’s eye color is now set. Baby’s lungs and brain are developed enough to function.	No special precautions needed.
Week 39	Signs of approaching labor may include more regular and frequent contractions, water breaking with leakage, and lower abdominal pain.	Baby’s organs are fully developed and in position. Baby is very active in the womb.	No special precautions needed.
Week 40	Doctors may perform a biophysical profile test, including a detailed ultrasound to check baby’s overall activity, heartbeat, breathing, muscle tone, and amniotic fluid levels. Doctors will also assess the cervix’s “ripeness,” including its position, softness, thinning, and dilation.	Baby’s nails and hair grow rapidly.	Cook and freeze meals that can be easily reheated for convenience.

*** The following information is provided by Bowtie ***

⚡Bowtie Pink Blog Promo!

Tired of sky-high private hospital bills but hesitant about purchasing VHIS? Bowtie Pink provides full coverage*, with long-term premiums are substantially lower than market rates^.

For a limited time, use the exclusive Bowtie Blog promo code【BLOGENGINSURE】to get an impressive 65% in first year’s premium and secure top-tier health protection at an unbeatable price!

^{*Full coverage shall mean no itemized benefit sub-limits, and applies to designated benefit items only. The benefit payable shall be subject to the remaining deductible (if applicable), annual benefit limit, lifetime benefit limit and other limitations such as reasonable and customary charges, a pre-existing condition, “List of Designated Hospitals in Mainland China” and receiving medical treatment in the United States. For detailed terms and conditions, product risks, and exclusions, please refer to the relevant product website and policy.}
^{^For example, with Bowtie Pink (Ward) and the deductible option HK$80,000, the monthly premium for a 30-year-old non-smoker is HK$197. The premium comparison above is based on similar medical insurance plans with the ward level (data source on 27, July 2023), HK$50,000 to HK$80,000 deductibles, for a 30-year-old non-smoker. Different medical insurance plans have different coverage and benefit limits. For details, please refer to the relevant insurance policy and its terms and conditions.}

Sources

Author

Bowtie Team

The Bowtie Life Insurance Company Limited is an authorized life insurance company and Hong Kong’s very first virtual insurer approved. Through the use of modern technology and medical expertise, Bowtie offers an agent-free, commission-free and more convenient online platform for customers to quote, apply and claim for Voluntary Health Insurance Scheme (VHIS) anytime anywhere. Bowtie is ranked first in the direct channel sales throughout 2021. Stay up to date at www.bowtie.com.hk