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First trimester of pregnancy

First trimester of pregnancy


Pregnancy test showing two lines? Congratulations you are already in the First trimester of pregnancy! In our content, you will find everything about what will happen to your body and how the child will develop. Here is everything important you need to know about necessary medical examinations, diet and daily routine features, permissible physical activity, etc.

Pregnancy is counted in two ways.

The obstetric gestation period is counted from the 1st day of the last menstruation since then the egg is fertilized by sperm and begins to mature.

The total duration of the obstetric period is 40 weeks, and it is on him that doctors are guided when they are pregnant. The results of ultrasound studies are also interpreted based on obstetric counting.

The true gestational age is counted from ovulation and conception, 2 weeks shorter than obstetric. Doctors don’t use this method of counting since it’s impossible to determine ovulation and conception without medical supervision accurately.

As you know, the waiting time for a baby is 9 months, and this period is usually divided into three equal parts: the 1st, 2nd and 3rd trimesters.

The 1st trimester includes the 1st, 2nd and 3rd months of pregnancy and lasts from the 1st to the 13th obstetric week inclusive.

Week of pregnancyChanges in baby
1st and 2nd week pregnancyFollicles mature in the ovaries. No baby has formed yet
3rd weekThe embryo moves through fallopian tubes and attaches to the uterine wall. development of the nervous system begins
4th weekThe embryo begins to influence the hormonal background. the possible onset of toxicosis
5th weekDevelopment of the nervous system (nervous and cardiovascular systems) laid. deficiency of folic acid may cause disturbances in the formation of the neural tube
6th weekThe embryo has a head and chord. Brain and spinal cord form. Circulation of blood begins. A deficiency of iron may affect normal development. ears and eyes outlined
7th weekThe umbilical cord is formed. nutrient and oxygen supply, as well as excretion of metabolic products, accelerated
8th weekThe head is clearly framed, and facial features are distinguishable. Bone and cartilage tissue formed (calcium is needed for density). retina begins to form in eyes (omega-3, potassium, vitamins A, B1, B2, B12, B6, C needed for development). external genital organs formed
9th weekPlacenta formation is complete, and the baby is better protected from adverse external factors. The heart becomes four-chambered. Eyelids on eyes have formed.
10th weekThe genitourinary system begins to work. kidneys excrete urine, sex cells formed in genital organs
11th weekThe main organs of the baby are formed. the fetus needs to grow actively
12th weekThe fetus makes swallowing movements. The brain is divided into the cerebellum and two hemispheres. Blood tests can determine group and Rh factors.
13th weekThe formation of all organs of the fetus is completed and the placenta is formed.
Changes in baby, fetus by week in first trimester

What happens to body of the pregnant mother in First trimester?

The 1st trimester is both a happy and a difficult time for a pregnant woman. 

Her well-being and body are changing and must be accepted, discussing any worries with her obstetrician-gynecologist and other doctors.

Nausea in the morning:

Toxicosis is the most famous symptom of pregnancy. It is familiar to 60-80% of expectant mothers and is caused by hormonal changes. Also, nausea can be provoked by a deficiency of vitamins and minerals or a sharp drop in blood sugar levels. Toxicosis begins at the 2–3rd or 4–5th week of pregnancy and ends at the 12–14th. Medical attention is needed if an unpleasant symptom lasts longer or overtakes late in pregnancy. If vomiting is more than 5 times a day, then a doctor’s supervision is also required to avoid the threat of miscarriage due to dehydration.

Problems with digestion:

Due to hormonal games, expectant mothers can have a strong appetite, and its complete absence, constipation (this is generally a common problem during pregnancy, a dangerous threat of miscarriage), and diarrhea. And food addictions reactions to smells also change. 

Weight set:

The approximate rate of weight gain in the first trimester is 1-2 kg. This indicator varies, taking into account the individual characteristics of the pregnant woman’s health: shortage, overshoot or the norm on the scales, the doctor decides.

More frequent urination:

Throughout pregnancy, the urge to go to the toilet will be more frequent: the more the uterus increases in size, the more it presses on the bladder. Changes in the hormonal background also affect: an increase in the level of progesterone in the blood provokes more consumption and, accordingly, the release of fluid.

Bloody discharge:

A small discharge of blood from the vagina occurs in 75% of pregnant women in the first weeks of the term. It means that the fetus has undergone implantation – fixed in the uterus. Important! Smearing bleeding may indicate an ectopic pregnancy. Severe bleeding may indicate a miscarriage, and medical assistance is needed.

Breast swelling:

The mammary glands slightly increase and become more sensitive (up to painful sensations), as before the onset of menstruation. So the body of the expectant mother begins preparation for breastfeeding.

Feeling tired and drowsy, fainting:

Hormonal changes increase progesterone production, spasm the blood vessels, congest them, and lower blood pressure.

Baby development by month during first trimester

Baby at first trimester Ultrasound at first trimester
Baby at first trimester , Ultrasound at first trimester

Along with the joy of realizing that you are expecting a baby, anxiety arises for him: the first 3 months are the most dangerous in terms of miscarriage statistics and the most important for forming a child’s health.

1st month of first trimester. 

After sexual intercourse fertilization occurs – the fusion of male and female germ cells (sperm and egg) in the fallopian tube. The resulting new cell called zygote enters the uterus and is fixed. An embryo is formed with the rudiments of the skeleton and muscles, the digestive tract, the cardiovascular, nervous, and urinary systems, and the placenta and umbilical cord. By the end of the month the embryo’s size is 4–5 mm.

2nd month of first trimester. 

The embryo shows the rudiments of arms and legs with fingers. The neck, the rudiments of the sense organs, and the genital organs are formed. The brain begins to coordinate the work of other organs. A heartbeat appears the stomach secretes gastric juice, and the liver performs hematopoiesis function. The embryo is already considered a fetus at the end of the second month. Its size reaches 25-30 mm, while the size of the head is equal to half the “growth” of the fetus.

3rd month of first trimester. 

Eyelids, rudiments of nails and hair, and urogenital and anus openings are formed, and ossified areas appear in the cartilaginous skeleton. The fetus already has facial expressions and can move its arms and legs. The shape of the external genitalia can determine the sex of the unborn child. The length of the fetus is 7–8 cm, while the head remains large relative to the proportions of the body.

Having twins in First Trimester of pregnancy

Statistics say: for every 87–90 pregnancies, there is one pregnancy with twins (according to other sources, 3 cases out of 100). For future parents, especially for mothers, this is double happiness and double responsibility. 

What is important to know?

  • Twins can be monozygous (and then twins will be born) and dizygotic (Two mature eggs are fertilized and born babies of even of the same sex will not be outwardly copies of each other). The presence of fraternal twins is determined by ultrasound at the 4–5th week of pregnancy and identical twins – at the 12th week.
  • With multiple pregnancies, the hCG hormone level in the expectant mother’s body is 2 times higher than during normal pregnancy.
  • In general, the future mother’s well-being twice does not differ from the state of health of those expecting one baby, although toxicosis, anemia, heartburn, back pain and weight gain may be more pronounced. The ideal weight gain with twins in 9 months should be at least 7 kg and not more than 18-20 kg.
  • The predisposition to multiple pregnancies is genetically transmitted (usually through a generation), and the chance of getting pregnant with twins is higher in women aged 30-40+. Scientists explain this by a safety net of the body, which is programmed by nature to continue the race. Also, the predisposition to the conception of twins is affected by the refusal of oral contraceptives against the background of their long-term use, infertility treatment, and IVF.
  • Twins develop in utero at the same pace as babies with a singleton pregnancy, but, as a rule, they have less weight and size (however, they easily catch up with their peers after birth in this parameter). So, by the end of the 1st trimester, both fetuses reach 6 cm in length and weigh about 8 g each.

Difficulties bearing

Hormonal disruptions, poor heredity, severe stress, maternal diseases and other adverse factors can lead to fetal defects and loss. In many cases, you can cope with the difficulties of bearing if you are under the supervision of doctors and follow their recommendations.


 Medical statistics say that 15-20% of pregnancies (approximately every fifth conception) end in spontaneous abortion when the mother’s body rejects the fetus. Moreover, more than 80% of miscarriages occur in the 1st trimester. There are many reasons for the loss of a child. Among them are bad ecology (including difficult working conditions), bad habits, natural selection (wise nature gets rid of a non-viable embryo), TORCH infections that the expectant mother gets, and an earlier abortion.

Non-developing pregnancy:

10-15% of pregnancies stop in development, ending in the fetus’s death. Most often, this happens for up to 28 weeks, and the most dangerous are the weeks of the 1st trimester, although, unfortunately, the fetus can stop developing in the later stages. The causes of pregnancy fading are similar to the factors that provoke miscarriage: from bad habits and side effects of certain medications to genetic predisposition, stress and abortions.

Ectopic pregnancy:

1-2% of pregnancies are cases where the fetal egg is attached not inside the uterus but inside one of its two tubes or, less often, to the cervix or ovary. Pathology can be detected at 3-4 weeks of pregnancy with the help of ultrasound and a blood test for hCG (the level of this hormone will be lower than when carrying a fetus that is properly fixed in the uterus). Starting from the 4-5th week, the expectant mother with an ectopic pregnancy is at risk: the growing fetus leads to rupture of the tube and internal bleeding – a threat to the health and life of a woman. The doctor decides which way to remove the fetal egg: surgical or chemical. The causes of an ectopic pregnancy may be the bad habits of the expectant mother and her abortions, inflammatory diseases of the uterine appendages, operations on the fallopian tubes, previous ectopic pregnancies, the use of an intrauterine device as a contraceptive, etc.

Development of fetal pathologies:

Approximately 5% of healthy couples become parents of special children – with mental or physical developmental disorders. At the same time, according to the World Health Organization, malformations can be caused by genetic, infectious, socio-economic or environmental reasons. 

Remember: Before diagnosing a disease in a child, double-check the diagnostic data with additional examinations from multiple specialists. With today’s medical technology, many diseases can be corrected either prenatally or after birth.

Do’s and don’ts of First Trimester of Pregnancy.

Do’s of First Trimester

  • Give up bad habits (smoking, drinking alcohol, drugs).
  • Get enough sleep (norm – 8-9 hours sleep).
  • Switch to regular but light fitness training: jogging, Nordic walking and regular walking, yoga for pregnant women, swimming and water aerobics.
  • Observe the “rule of clean hands” to prevent infectious diseases.
  • Avoid overwork and stress.
  • Take multivitamins and supplements in consultation with your doctor.
  • Eat regularly and properly.

Don’ts of First trimester

  • Take any medications without the doctor’s approval.
  • Give yourself intense exercise.
  • Wear uncomfortable, tight clothing, underwear and shoes because these impair blood circulation.
  • Undergo X-ray examinations.

Nutrition guides for first trimester 

Vitamin/MineralBenefits for Pregnant WomenBenefits for Unborn Child
Folic acid (vitamin B9)Reduces risk of congenital malformations of nervous and cardiovascular systems of fetus, reduces risk of miscarriageN/A
Vitamins B6 and B12Helps prevent anemia, alleviates manifestations of toxicosisNecessary for full development of fetus
Vitamin ENormalizes metabolism, maintains elasticity of skin, reduces risk of miscarriageNecessary for full intrauterine development of child
Vitamin DNecessary for formation of bone tissue, prevents rickets in childN/A
Vitamin CStrengthens immune system, strengthens blood vessel wallsN/A
Vitamin ANecessary for formation of baby’s organ of visionN/A
IodineImportant for normal functioning of mother’s thyroid gland, necessary for full mental and physical development of unborn childN/A
CalciumIndispensable for formation of child’s skeleton, replenishes calcium losses in woman’s bodyN/A
IronNecessary for hematopoiesis, prevents iron deficiency anemiaN/A
ZincAvoids fetal malformations, underweight in newborns, positively affects immune system, skin, hair and nails of expectant motherN/A
LuteinImproves visual acuity of mother, positively affects development of brain of unborn childN/A

The expectant mother should not eat for two, but for two, that is, pay attention not so much to the quantity as to the quality of food: its freshness, saturation with vitamins and minerals, balance in the content of fats, proteins and carbohydrates. And remember, your diet should be discussed with your doctor.

Basic principles of healthy eating in First trimester:

Fruits and berries : 3-4 servings per day. 1 serving = 1 fresh fruit = 1 cup berries = 1/2 cup canned fruit = 1/4 cup dried fruit = 3/4 cup fresh juice. You must have an apple and citrus fruit in your diet every day (if you are not allergic), and it is better to drink juice with pulp to retain fiber that is useful for digestion.

Vegetables : 3-5 servings per day. 1 serving = 1 cup fresh leafy vegetables = 1/2 cup fresh or boiled, baked fruits and roots. The menu of the expectant mother must certainly include lettuce, spinach, green onions, white cabbage, broccoli, carrots, potatoes, pumpkin, bell peppers, and tomatoes.

Dairy products : 3 servings per day. 1 serving = 1 glass of milk or yogurt = 50 g of hard cheese = 100 g of cottage cheese. Dairy products provide you and your baby with the calcium needed for a healthy and strong musculoskeletal system.

Protein: 2-3 servings per day. 1 serving = 60-85 grams of meat, poultry or fish = 1 cup legumes = 2 eggs = 1/4 cup nuts. You and your baby need vegetable and animal protein as a “building material”: lean meat, poultry, fish, eggs, lentils, beans, peas, nuts, sunflower seeds and pumpkins.

Whole grains : 3 servings per day. 1 serving = 1 slice of bread or cracker, loaf = 1/2 cup cereal or cereal side dish = 50g pasta or pasta. The fiber contained in these products supports the normal functioning of digestion, and helps prevent constipation and hemorrhoids.

What vitamins are needed in first trimester

As you know, a modern person does not get enough vitamins and minerals with food, so he makes up for what he needs by taking multivitamin complexes. The expectant mother for excellent health and her baby for the full development in the 1st trimester especially need such useful nutrients as:

Fitness for pregnant mothers in First trimester

Moderate physical activity benefits a woman expecting a baby. It helps to stay in good shape, suffer less toxicosis, protect the fetus from oxygen starvation, and maintain a positive emotional mood.

Fitness activities in the 1st trimester have limitations because the fetal egg needs time to finally gain a foothold in the uterus and be protected by the placenta (it appears at 12–14 weeks and begins to function at 18–20 weeks of pregnancy fully). Be sure to coordinate your type and training regimen with your doctor and stop exercising (change to another load) if they bring physical discomfort to you and your baby!

What’s allowed:

  • Breathing exercises.
  • Walking at a leisurely pace.
  • Fitness ball exercises.
  • Water aerobics.
  • Yoga programs and Pilates for pregnant women.
  • Light stretching.
  • Gymnastics for pregnant women.

What to avoid in First trimester:

  • Intense cardio training.
  • Workouts with twists, squats, sharp bends, jumps, and swings.
  • Strength sports, martial arts.
  • Cycling, tennis, rollerblading and cycling, and horseback riding.
  • Running for speed and endurance.
  • Intense stretching.

The most common diseases during first trimester

The 1st trimester is the very beginning of pregnancy, so any diseases of the expectant mother can negatively affect the baby, because his body is just being formed. Not a single symptom of ill health, even a “banal” runny nose or body temperature just above 37 degrees, a woman in position should not be ignored, as well as self-medicate. Do not postpone the visit to the doctor and follow his instructions exactly!

The most common diseases of expectant mothers in the 1st trimester of pregnancy are as follows:


Acute respiratory diseases caused by viruses, bacteria and other microorganisms include influenza, tonsillitis, rhinitis, pneumonia, sinusitis, pharyngitis, bronchitis, laryngitis, etc. Airborne droplets transmit them and household means and cause inflammatory processes in the airways. These infections increase the risk of fetal abnormalities, miscarriage, and miscarriage.

Prevention: influenza vaccination; compliance with the rules of personal hygiene; wearing a gauze mask in public places and at home if there is a sick person in the family; regular ventilation; lubrication of the nasal mucosa with oxolin ointment, viferon


A viral disease in the form of itchy rashes-bubbles that affects the skin (not only the lips!) And mucous membranes. Attacks the body when the immune system is weakened. Herpetic infection can provoke the development of fetal heart defects, disrupt the formation of the gastrointestinal tract, and cause cerebral edema – hydrocephalus.


Practicing good hygiene and avoiding contact with people with herpes when they are in the acute phase.


Difficulty defecation or a feeling of incomplete emptying worries expectant mothers because the hormonal changes in their body affect the work of the intestines. The muscle tone of the pelvic organs is weakened under the influence of hormones so that the embryo can safely “settle down” in the uterus, but the woman’s bowel functions suffer because of this. Also, the causes of constipation in pregnant women are non-compliance with the drinking regime, unbalanced nutrition and a sharp restriction of physical activity. Frequent constipation not only causes discomfort to the mother and the baby but also provokes the appearance of hemorrhoids, dysbacteriosis, and inflammatory processes in the pelvic organs and increases the risk of miscarriage.

Prevention: To maintain regular bowel movements, consume adequate fluids and fiber-rich foods, such as dried fruits, fruits, berries, and vegetables. You can also use glycerin suppositories and stay physically active.


At least 75% of women at least once fall ill with vaginal candidiasis, nicknamed thrush for its characteristic cheesy-white discharge. The cause of the disease is fungi of the genus Candida, which, for one reason or another, begin to actively multiply and exceed their normal number in the microflora of the female body. In expectant mothers, thrush occurs 2-3 times more often than in non-pregnant women since changes in hormonal levels affect the immune system and the balance of microflora. Candidiasis complicates the course of pregnancy. In more than 70% of cases, it is transmitted to the child, which is especially dangerous if he is born prematurely.

Prevention: Maintaining intimate hygiene, avoiding refined foods high in sugar and other carbohydrates, wearing cotton underwear, taking antibiotics only as prescribed by a doctor, and preventing hypothermia are all important for good health.


Inflammation of the mucous membrane of the bladder makes itself felt with frequent painful urination, cloudy sediment or blood in the urine, pain in the lower abdomen, and fever. Pregnancy can weaken a woman’s immune system and cause hormonal changes, leading to cystitis. If not treated, cystitis can develop into pyelonephritis, an inflammatory kidney disease that poses a risk to both the mother and baby.

Prevention: Maintain intimate hygiene, drink plenty of fluids, follow a special diet, wear loose-fitting cotton clothing, and avoid hypothermia.


An unpleasant burning sensation occurs due to the ingestion of the contents of the stomach into the esophagus. In expectant mothers, heartburn is usually due to a hormonal shift: the hormone progesterone relaxes the gastrointestinal tract muscles, and gastric juice easily enters the esophagus. This does not affect the child’s health, but his mother causes considerable discomfort.

Prevention: A balanced diet should restrict or exclude foods high in fat, sugar, and other fast carbohydrates, as well as carbonated drinks. Additionally, tight clothing should be avoided. And it is not recommended to rest or do activities involving bending or lifting weights immediately after eating.

First trimester checklist

  1. Register at the parental clinic.
  2. Complete scheduled examinations and tests.
  3. Normalize diet and daily routine.
  4. If possible, postpone dental treatment until the 2nd trimester of pregnancy. If a visit to the dentist is unavoidable, inform them of what week of pregnancy you are in.
  5. Make a shopping list that includes things for yourself in late pregnancy and a dowry for a newborn.
  6. Before the baby arrives, a list of tasks needs to be completed, such as moving, repairing, buying furniture, and removing unnecessary items.
  7. Postpone coloring or perming your hair until the 2nd trimester
  8. Quit smoking and other bad habits.
  9. Make friends with a type of fitness that is comfortable for you personally and suitable for pregnancy.
  10. Find online and offline friends and like-minded women among other expectant mothers.
  11. To study information about the intrauterine development of the child and the changes occurring in a pregnant woman’s body.
  12. Start a new one or continue your old creative hobby.

Tips for First trimester

Find a doctor you trust: Not always the obstetrician-gynecologist to whom you are “attached” in the antenatal clinic suits you as a specialist and person. Visit several doctors of the same profile, and you will be able to find, as a safety net, the doctor with whom you will feel comfortable during your entire pregnancy. Ask friends, relatives or colleagues who have already become a mother to recommend such a specialist.

Start Stretch Mark Prevention: As a result of strong tension on the skin of the growing abdomen and the chest and thighs, scars (striae) may appear – a consequence of the rupture of collagen fibers. You can prevent the appearance of stretch marks and make existing ones less pronounced by applying a moisturizer or special medical cosmetics to the skin daily. You also need to remember to drink at least 1.5 liters of liquid (preferably plain drinking water, not tea, juices, etc.) per day, consume enough protein and minimize pastries and sweets.