Pregnancy Symptoms Week by Week
Pregnancy is a normal physiologic process for the development of human beings and it is necessary process to produce offspring.
Pregnancy starts with conception where egg (ovum) is fertilized with a mature sperm. After fertilization, implantation occurs in the uterus of female to continue further development of embryo.
Here we will discuss week by week pregnancy symptoms. Pregnancy spans 280 days and it is usually divided into three trimesters, with 3 months in each trimester. In 1st trimester all major organ systems are developed; while in 2nd semester fetus can be visualized by ultrasound to see anatomic details of fetus and in 3rd trimester fetus can survive, even if it is born as a preterm baby. 35th week is important landmark and at this stage weight of fetus is 2500 grams. It determines the maturity of fetus.
Week 1 (Ovulation to Implantation)
- Mature ovum is produced by ovary and it is expelled into uterus for fertilization.
- Some females feel pain at the time of ovulation, it is called mittelschmerz.
- In case of successful fertilization, Zygote is formed which is earliest form, and from which further development of embryo takes place.
- Zygote further divides and its implantation is started in the inner side of uterus.
- No visible changes observed in second week of pregnancy in mother.
- Implantation is completed by the end of second week.
- In this week there is risk of ectopic pregnancy as it depends upon the site of implantation. Most common site of ectopic pregnancy is uterine tube so it is called tubal pregnancy. It is very threatened type of pregnancy as it may lead to maternal death.
- Most frequent symptoms of pregnancy are observed in the end of 3rd week which among which most important symptoms are;
- Time of onset may be variable and unexpected bleeding may occur as a consequence of implantation.
- 3rd week is much important because fate of most organ system, eyes, heart and brain is accomplished in this week.
- 3rd week is much vulnerable to teratogenic insults which lead to abnormal development of fetus. Mothers taking antidepressants such SSRIs during pregnancy may lead to heart abnormalities in fetus. Many other examples of teratogens are smoking, drinking alcohol etc.
- In this week most of the females feel tiresome, may experience frequent urination and they are usually short-tempered.
- Slight breast tenderness is observed in this week.
- hCG hormone is raised is in urine so pregnancy test can be done for confirmation.
- No weight gain is observed till the end of 4th week of pregnancy.
- Various organs are formed in this week, such as primitive heart and neurulation or formation of central nervous system (CNS).
- Fetus is attached to uterus via placenta which starts secreting hCG hormone.
- By the end of this week, embryo is still to light too be weighed.
- Breasts become more tender, and to some extent, it may be aching.
- Tiredness, morning sickness and bloating are also observed.
- Urination frequency is increased.
- These symptoms are observed till the end of 1st trimester of pregnancy.
- Till is stage, embryo is made up of three embryonic layers from which further development of other organs takes place:
- Ectoderm: it gives rise to CNS, ear, nose, eyes, skin including hair, nails and teeth.
- Mesoderm: it forms muscles, cartilages and bones.
- Endoderm: it gives rise to lungs, intestine and urinary bladder.
- Symptoms described above such as nausea, vomiting, morning sickness including increased sense of smell get more intensified and these symptoms will persist up to 1st trimester. Mood swings are observed due to fluctuating hormonal influences.
- Elbows, hands and fingers develop from upper limb buds.
- Legs develop from lower limb buds.
- Heartbeat can be detected by ultrasound.
- External ear is formed.
- Breast tenderness, nausea, vomiting, headache and food craving like symptoms are observed as given above.
- Length at this stage is 13 to 22 mm.
- Fingers become prominent, eyelids are formed
- Symptoms present at this time are morning sickness, fatigue, urinary urgency and breast tenderness.
- Length at this stage is 21 to 31 mm.
- Limbs become long, toes become free, and tail disappears.
- By the end of this week, embryo has all the distinct characteristics of human being.
- Face appears human-like.
- As enzymes are fluctuating in pregnancy, indigestion and heartburn is observed.
- Breasts are tender and waistline is growing with the passage of time.
- Development of heart is completed.
- Development of tongue begins and larynx is growing.
- Eyelids are completely formed but remain closed.
- In this week, women get some relief from morning sickness and feel better to some extent.
- Breasts and abdomen are tender.
- Blood flow to uterus, breast and skin is increased.
- From this week to birth, embryo is called fetus.
- Fetus floats in the amniotic fluid.
- Fetus has 50mm length.(Crown rump length)
- Ears and nose are prominent.
- Muscles of body are formed.
- Women start weight gaining in this week.
- Balanced diet and daily exercise is recommended for a healthy pregnancy.
- Nausea and fatigue are common and constant symptoms in early pregnancy.
- Breasts remain tender.
- Fingernails development starts in this week and continues growing for several months.
- Length of fetus is 61mm (CRL).
- External genitalia become visible but it is too early to differentiate between baby boy or baby girl.
- Weight gain is continued in this week.
- Women start getting relief from uncomfortable symptoms of early pregnancy such as nausea and fatigue. Women feel some energy at this level.
- Placenta is now fully developed.
- Headache and dizziness is experienced.
- Constipation is another complaint in pregnant women which can be prevented by use of dietary fibers.
- At this week, baby is considered fully developed.
- Fetus starts moving which can be detected by Doppler.
- Elbow and knee reflexes are present.
- Organs of fetus start functioning.
- 2nd trimester starts from this week and women feel better as symptoms of 1st semester (morning sickness and fatigue) subside. So, women feel energetic.
- Her appetite is increased.
- Bleeding gums are observed during cleansing of teeth, it subsides when pregnancy is over.
- In start of 2nd trimester, fingers and toes of fetus are prominently separated and fetus resembles the little human.
- Nose and chin are well differentiated.
- Eyes move closer and intestines migrate into abdomen.
- External genitalia are almost developed but sex cannot be differentiated till now.
- Uterus keeps on increasing its size for accommodation of fetus.
- Growing uterus also compresses the bowl in abdomen.
- So, flatulence, heartburn and constipation like symptoms are experienced.
- Blood vessels become engorged in abdomen and breast.
- Weight is continuously growing.
- Face started to be modified through bringing eyes toward center of face.
- Ears are placed on either side of head.
- Lanugo, soft hairs are produced throughout the body.
- Kidneys start producing urine, and fetus also starts meconium production.
- Fetus starts sucking thumb.
- In case of baby boy, prostate is developed, while in case of baby girl, ovaries descend down into pelvis.
- As the blood volume is increased and fluid retention also takes place so, ankles are swollen.
- As weight is increasing so, clothes may cause discomfort.
- Insomnia is also experienced.
- Fetus body comes in a proportionate pattern as the size of head is decreased as compared to the rest of body.
- Lanugo, the soft hairs act as insulator of body.
- Blood vessels of fetus are visible as skin is very thin.
- Other structures and organs like muscles and bones continue growing.
- Weight gain is up to 7lb in this week.
- Further increase in weight may cause health issues so it can be prevented by taking balanced diet. If this problem is not solved, consult with family doctor as it may be harmful for both mother and baby.
- Head and dizziness is experienced due to fluctuating blood pressure.
- Hairs grow on scalp which may have color.
- Muscles of face are now developing which will helpful in facial expression in future.
- Skin becomes itchy due to stretching over abdomen and breasts.
- Stretch marks, dark lines (linea nigra), skin pigmentation and bleeding gums are observed.
- Swelling of ankles is experienced; it can be prevented by taking plenty of fluids.
- Weight gain, flatulence, heart burn and indigestion are also experienced.
- Sugar level must be observed to rule out the gestational diabetes.
- As ears are fully developed, so fetus can hear sounds.
- Fat begins to accumulate beneath the skin of baby as it helps to maintain body’s temperature.
- Umbilical cord becomes thick and strong. It is also a route of nutrition supply to fetus.
- Retina has developed and become sensitive to light.
- As uterus size is increasing, stretch marks are observed on the abdomen and skin become itchy.
- Weight is also increasing due to increase in baby size and uterus size.
- Stretch marks are also seen on breast. It denotes the preparing of the breast for nursing.
- Back pain, swollen legs and ankles, and round ligament stretching cause pain.
- Fetus is growing faster at this stage.
- Baby can hear mother’s heartbeat.
- Baby has a pattern of sleep and awake.
- Quickening (first movements of fetus) are felt by mother
- Indigestion and heartburn are constantly experienced symptoms due to decreased motility of gut.
- Skin rashes develop on the stretched skin.
- Thin skin of fetus is now developing a protective whitish fatty layer called vernix caseosa.
- Baby is frequently moving in amniotic sac.
- Symptoms like heartburn and indigestion are following the increasing size of uterus.
- As already described about swelling of ankle and lower leg which can be prevented by ingesting plenty of fluids.
- At this stage, average weight gain is 5 to 10 pounds.
- Fetus is growing and organs are now being placed at their proper place.
- Kidney gets its normal bean shaped.
- External genitalia become more pronounced and recognizable.
- Increased appetite due to increased demand of calories to body.
- Pregnancy related Backache is due to force of gravity.
- Constipation, backache and edema (swelling) of lower limbs can be prevented by slight exercise.
- Baby is learning about swallowing reflex by ingesting amniotic fluid.
- Development of nail beds has been completed and now fingernails and toenails growth has begun.
Week 22 to week 25
- Increase in libido due to increase in breast size in week 22.
- Swelling of feet makes uncomfortable wearing shoes.
- Increase in weight is up to 15 pound
- Anxiety becomes prominent in week 23
- Contractions occur in body in week 24 which may be irregular, painless; such contractions are called Braxton-Hicks contractions. If these contractions are regular, then consult with family doctor to rule out preterm labor.
- Backache, frequent urination, nightmares, patchy discolored skin.
- Weight gain is one pound per week afterwards till pregnancy
- Eyelids and eyelashes are formed completely in week 22.
- As sensory retina is developed, fetus responds to dark and light.
- Skin is much wrinkled as it is due to rapidly growing skin.
- Fingernails are present and eyelids are fused till now.
- Lungs, brain and taste buds are developing.
- By the end of this stage (after 24 weeks) fetus can be saved so called viable fetus.
Week 26 to 29
- Fatigue, lower limb cramps, sleep disturbances is experienced.
- Prenatal checkups are recommended after every two weeks.
- Breast size is increased and amniotic fluid is also increasing to protect the baby.
- Backache and discomfort is present.
- Eyelids are now separated due to break down of fusion.
- Fat is accumulated beneath the skin and wrinkling of skin is starting to disappear.
- Toenails are now prominent.
- In baby boy, testes descend to reach inguinal canal.
- If premature baby is born, he can survive due to complete development of lungs and brain
Week 30 to 34
- Breathlessness is experienced as growing uterus imparts pressure over the lungs.
- Vital sign and baseline should be monitored to rule out complications in pregnancy and at the time of delivery.
- Weight is increasing consistently, one pound every week.
- Increasing pressure by uterus may cause varicose veins, leg cramps and hemorrhoids.
- Urinary frequency is increased. Other symptoms of 1st trimester which were subsided, in week 33 these appear again such as fatigue, nausea, vomiting and flatulence.
- Dizziness and forgetfulness may be present.
- Braxton Hicks contractions which are painless and irregular in nature may be present.
- More fat is deposited under the skin, so now skin becomes smooth.
- Lanugo, soft hairs now disappear from face.
- Fingernails are now completely formed.
- White cheese like layer called vernix caseosa over the skin become thicker which is protective for fetus.
- In baby boy, left testes reach to testes.
Week 35 to 38
- All the symptoms described above become more intense.
- Braxton Hicks contractions become more severe and it is preparation of delivery.
- Weight is still increasing and it is round about 25-35 pounds.
- Regular contractions increase during walk.
- Cervix moves down and forward toward opening of vagina.
- Breast becomes large and black pigmented areola also covers a large area. Milk is leaked out from breast, this milk is called colostrum.
- Edema (swelling) of feet and legs is present.
- Symptoms of labor are observed; such as diarrhea, contractions, discharge from vagina which may be bloody.
- Plentiful fat has been accumulated and fetus appears as round.
- Lanugo, soft hairs now disappear from most of body except shoulder region.
- In baby boy, both testes reach down in scrotum.
- Now Nails grow beyond tip of fingers and toes.
Week 39 & 40
- Labor symptoms become intense. Be careful and inform your health care provider.
- Mucus plug is present at cervical os, preventing against bacteria.
- Other symptoms experienced are constipation, difficulty in breathing, fatigue and insomnia.
- Labor may occur any time in week 40.
- Baby is formed completely and ready to deliver. In other words, the fruit is ripened for which you sowed nine months back!
- Circumference of head is larger than other parts of body and it is important factor regarding to passage of fetus through birth canal.
- Countdown My Pregnancy. Pregnancy week by week [online] 2013 last updated [Cited 2013, May 1]. Available from: http://www.countdownmypregnancy.com/pregnancy/pregnancy-week-by-week.php.
- Kidz Health. Pregnancy Calendar [online] 2012 last updated [Cited 2013, May 1]. Available from: http://kidshealth.org/parent/pregnancy_calendar/.
- Owe KM, Nystad W, Skjaerven R, Stigum H, Bo K. Exercise during pregnancy and the gestational age distribution: a cohort study. Med Sci Sports Exerc 2012; 44(6):1067-74.
Published by Dr. Jackie Te RN, MD under Women's Health and Pregnancy.
Article was last reviewed on January 12th, 2022.