• Contact us
• About us
• A-Z topics
• Symptom Checker
• Service Finder
• Linking to us
• Information partners
• Terms of use
• Privacy

Pregnancy, Birth and Baby is funded by the Australian Government and operated by Healthdirect Australia.

Pregnancy, Birth and Baby is provided on behalf of the Department of Health

Pregnancy, Birth and Baby’s information and advice are developed and managed within a rigorous clinical governance framework. This website is certified by the Health On The Net (HON) foundation, the standard for trustworthy health information.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

Except as permitted under the Copyright Act 1968, this publication or any part of it may not be reproduced, altered, adapted, stored and/or distributed in any form or by any means without the prior written permission of Healthdirect Australia.

Support this browser is being discontinued for Pregnancy, Birth and Baby

Support for this browser is being discontinued for this site

• Internet Explorer 11 and lower

We currently support Microsoft Edge, Chrome, Firefox and Safari. For more information, please visit the links below:

• Chrome by Google
• Firefox by Mozilla
• Microsoft Edge
• Safari by Apple

You are welcome to continue browsing this site with this browser. Some features, tools or interaction may not work correctly.

Pregnancy - week by week

The unborn baby spends around 38 weeks in the womb, but the average length of pregnancy (gestation) is counted as 40 weeks. This is because pregnancy is counted from the first day of the woman’s last period, not the date of conception, which generally occurs two weeks later.

Pregnancy is divided into three trimesters:

• First trimester – conception to 12 weeks
• Second trimester – 12 to 24 weeks
• Third trimester – 24 to 40 weeks.

Conception

The moment of conception is when the woman’s ovum (egg) is fertilised by the man’s sperm. The gender and inherited characteristics are decided in that instant.

Week 1

This first week is actually your menstrual period. Because your expected birth date (EDD or EDB) is calculated from the first day of your last period, this week counts as part of your 40-week pregnancy, even though your baby hasn’t been conceived yet.

Week 2

Fertilisation of your egg by the sperm will take place near the end of this week.

Week 3

Thirty hours after conception, the cell splits into two. Three days later, the cell (zygote) has divided into 16 cells. After two more days, the zygote has migrated from the fallopian tube to the uterus (womb). Seven days after conception, the zygote burrows itself into the plump uterine lining (endometrium). The zygote is now known as a blastocyst.

Week 4

The developing baby is tinier than a grain of rice. The rapidly dividing cells are in the process of forming the various body systems, including the digestive system.

Week 5

The evolving neural tube will eventually become the central nervous system (brain and spinal cord).

Week 6

The baby is now known as an embryo. It is around 3 mm in length. By this stage, it is secreting special hormones that prevent the mother from having a menstrual period.

Week 7

The heart is beating. The embryo has developed its placenta and amniotic sac. The placenta is burrowing into the uterine wall to access oxygen and nutrients from the mother’s bloodstream.

Week 8

The embryo is now around 1.3 cm in length. The rapidly growing spinal cord looks like a tail. The head is disproportionately large.

Week 9

The eyes, mouth and tongue are forming. The tiny muscles allow the embryo to start moving about. Blood cells are being made by the embryo’s liver.

Week 10

The embryo is now known as a fetus and is about 2.5 cm in length. All of the bodily organs are formed. The hands and feet, which previously looked like nubs or paddles, are now evolving fingers and toes. The brain is active and has brain waves.

Week 11

Teeth are budding inside the gums. The tiny heart is developing further.

Week 12

The fingers and toes are recognisable, but still stuck together with webs of skin. The first trimester combined screening test (maternal blood test + ultrasound of baby) can be done around this time. This test checks for trisomy 18 (Edward syndrome) and trisomy 21 (Down syndrome).

Week 13

The fetus can swim about quite vigorously. It is now more than 7 cm in length.

Week 14

The eyelids are fused over the fully developed eyes. The baby can now mutely cry, since it has vocal cords. It may even start sucking its thumb. The fingers and toes are growing nails.

Week 16

The fetus is around 14 cm in length. Eyelashes and eyebrows have appeared, and the tongue has tastebuds. The second trimester maternal serum screening will be offered at this time if the first trimester test was not done (see week 12).

Week 18-20

An ultrasound will be offered. This fetal morphology scan is to check for structural abnormalities, position of placenta and multiple pregnancies. Interestingly, hiccoughs in the fetus can often be observed.

Week 20

The fetus is around 21 cm in length. The ears are fully functioning and can hear muffled sounds from the outside world. The fingertips have prints. The genitals can now be distinguished with an ultrasound scan.

Week 24

The fetus is around 33 cm in length. The fused eyelids now separate into upper and lower lids, enabling the baby to open and shut its eyes. The skin is covered in fine hair (lanugo) and protected by a layer of waxy secretion (vernix). The baby makes breathing movements with its lungs.

Week 28

Your baby now weighs about 1 kg (1,000 g) or 2 lb 2oz (two pounds, two ounces) and measures about 25 cm (10 inches) from crown to rump. The crown-to-toe length is around 37 cm. The growing body has caught up with the large head and the baby now seems more in proportion.

Week 32

The baby spends most of its time asleep. Its movements are strong and coordinated. It has probably assumed the ‘head down’ position by now, in preparation for birth.

Week 36

The baby is around 46 cm in length. It has probably nestled its head into its mother’s pelvis, ready for birth. If it is born now, its chances for survival are excellent. Development of the lungs is rapid over the next few weeks.

Week 40

The baby is around 51 cm in length and ready to be born. It is unknown exactly what causes the onset of labour. It is most likely a combination of physical, hormonal and emotional factors between the mother and baby.

Where to get help

• Your doctor
• Obstetrician
• Midwife

Things to remember

• Pregnancy is counted as 40 weeks, starting from the first day of the mother’s last menstrual period. Your estimated date to birth is only to give you a guide. Babies come when they are ready and you need to be patient.
• The gender and inherited characteristics of the baby are decided at the moment of conception.

1st trimester of pregnancy: what happens to the fetus

1st trimester: 1st-12th weeks

The gestational age is calculated from the first day of the last menstruation, since it is difficult to determine the exact day of conception. Since conception usually occurs in the middle of the menstrual cycle, you are not actually pregnant during the first two weeks, but this period is counted as the beginning of pregnancy.

As soon as the fertilization of the egg takes place around the 3rd week, the hormones begin to produce changes in your body little by little. As a result, you may experience some of the following symptoms:

• Morning sickness. As a result of rising levels of hormones characteristic of pregnancy, up to 80% of women in the 1st trimester experience morning sickness with symptoms such as nausea and vomiting. The idea that such malaise is observed only in the morning is a common misconception. In fact, symptoms can appear at any time of the day or night. Up to 1 in 5 women experience morning sickness in the 2nd trimester of pregnancy and can sometimes persist throughout pregnancy.

  If you experience morning sickness, avoid foods that make you sick, eat little and often, avoid fatty and spicy foods, drink more water. If you experience severe symptoms or symptoms that bother you, see your doctor.

• Breast changes. The mammary glands will begin to increase in size, soreness may appear. The nipples will increase in size, become darker and more protruding.
• Fatigue. High levels of the hormone progesterone can make you feel tired and sleepy. Rest as often as possible in a horizontal position with your legs up and eat as well as possible, which is not easy if you are experiencing morning sickness!
• Increased emotionality. A higher level of emotionality, manifested as a result of an increase in hormone levels, is normal. Understanding and patience on the part of your partner and loved ones is very important here.
• Food likes and dislikes. You may find yourself intolerant of one food and addicted to another. This is usually not a problem, unless you feel like eating weird foods like chalk. If you are concerned about the situation, contact your doctor.
• Frequent urination. As your fluid levels increase and your uterus puts pressure on your bladder, you will become more likely to visit the toilet. Go to the toilet as soon as you feel the need - this minimizes the pressure on the bladder.
• Feeling of dizziness. Sometimes you may feel a little dizzy (this is due to hormonal changes). Try not to stay on your feet for a long time and slowly rise from a sitting or lying position. If you experience severe dizziness, contact your doctor immediately.
• Heartburn and constipation. Your digestive system will slow down to give you more time to digest your food. This can lead to heartburn and constipation. To help manage heartburn, try to eat small meals at regular intervals and avoid fried or spicy foods and carbonated drinks. Constipation is helped by eating a diet rich in fiber, maintaining physical activity and drinking plenty of water.

• Approximately 7 days after fertilization, the embryo implants in the uterine wall. The placenta, umbilical cord and amniotic sac will begin to form to provide nourishment and protection to the embryo.
• By the end of the first 12 weeks of pregnancy, the uterus is palpable through the wall of the abdomen, the abdomen will begin to grow.

By the end of the 1st trimester:

• All the main organs of the baby are formed, the circulatory system works.
• The development of the sexual organs has begun.
• Fingers are formed on the hands and feet, nails have appeared.
• Facial features have formed.
• The length of the baby's body is about 6 cm from the head to the lower part of the body, he is already recognizable. The baby moves in the amniotic sac, but you don't feel it move yet.

Clinic mobile app

You can make an appointment with a doctor, get tests
and much more...

Fill out the form to make an appointment or order a call back

I agree with personal data processing policy and user agreement I also give my consent to the processing of personal data.

Sign up for a consultation

I agree with personal data processing policy and user agreement I also give my consent to the processing of personal data.

By continuing to use rd.clinic23.ru, you agree to the use of cookies. How to ban the use of certain cookies can be found in Politics

1st trimester of pregnancy: everything you need to know | Mamovedia

The average gestation period is 40 weeks, counted from the date of the last menstrual period and measured in trimesters, months and weeks

The first trimester of covers the period from the 1st to the 12th week of pregnancy, which is approximately three months of the solar calendar. The second trimester starts at 13 weeks and ends at 27 weeks of pregnancy.
Finally, the third trimester covers the period from 28 weeks to the due date.

The first trimester of pregnancy is the most important for the development of your future baby.
During this period, the embryo (as the fetus of the first 8 weeks of life is defined) develops until it weighs from 14 to 28 grams, and growth, on average, from 7.5 to 10.5 centimeters.
Until the 20th week, the length of the embryo (and then the fetus) is usually measured from the head to the end of the spine. After that, its length is measured from head to toe.
The growth of the fetus in length will occur during the third, fourth and fifth months, and the increase in its weight will fall on the last two months of pregnancy.

What are the most common symptoms of pregnancy in the first trimester?

Usually the first symptoms accompanying pregnancy are nausea, vomiting, frequent urination, fatigue, breast tenderness . Many women begin to experience these symptoms even before a missed period or a positive pregnancy test result.

As your pregnancy progresses, you may begin to experience other symptoms such as mood swings, headaches, cramps, constipation, indigestion, bloating, food cravings or aversion, and an incredibly strong sense of smell: the latter often makes nausea worse.

Most of these symptoms, including mood swings and emotional outbursts, are believed to be caused by elevated levels of estrogen and progesterone.
If during this period you feel severe pain in the lower back, you have bleeding, severe nausea, it is recommended to consult a gynecologist, as these may be symptoms of a miscarriage.

First trimester weight gain

• Fetus. The weight gain of the fetus in the first trimester is negligible: at the end of the first trimester, it is actually the size of a peach.
• Expectant mother. Although the growth rate of the fetus is very subjective, the weight gain of the expectant mother by the end of the first three months should be about 1-2 kg.

During the first three months of motherhood, you can follow your regular diet and you don't have to eat for two!

Examinations and screenings during this period

As soon as you know you are pregnant, schedule your first appointment with your OB/GYN. The first examination is usually never done before the 8th week of pregnancy unless there is a risk of complications such as a history of abortion or a family history of hereditary genetic diseases. This visit is required for:

• check for any abnormalities in the growing embryo;

Testing for HIV, syphilis, rubella, hepatitis B, as well as asymptomatic bacteriuria, chlamydia, toxoplasmosis is generally recommended for all women.
Ultrasonography as part of prenatal screening for genetic chromosomal risks should be performed between weeks 9 and 12 , along with a biochemical blood test for beta-hCG, PAPP-A and PIGF (optional) with a geneticist's conclusion. The woman must be informed of the abnormalities that may be found in order to have the choice of whether to continue the pregnancy or not.

What does the baby look like in the 1st trimester?

At the end of the 1st month the embryo reaches the size from 2 to 5 millimeters . The heart and stomach are being formed in him, the sensory apparatus and the structure from which the nervous system will originate begin to develop. In addition, cavities for the eyes are formed and the very first sketches of future upper limbs appear.

By the end of the second month of embryonic development, the contours of the head and face begin to be drawn; nostrils, mouth, bronchi and lungs begin to form; brain grows; the very first sketches of the lower extremities appear; the upper limbs lengthen, acquiring the shape of a scoop. At this stage, the retina also begins to develop. At the end of the 2nd month, the embryo reaches a size of 2.3 centimeters and a weight of 15 grams . The heart of the embryo makes 110 beats per minute.

By the end of the third month, the elbows begin to bend, the eyelids and outer ear are defined, the corpus callosum appears in the brain between the two hemispheres, the formation of bones, nerves, muscles and great vessels continues. The growth of the body is observed.
Formed liver produces red blood cells and bile fluid; sketches of future external genital organs (penis in men; clitoris and labia majora in women) begin to develop, which is why it is possible to predict the future sex of the child at an early stage. Nails appear on the fingers; the intestine passes into the abdominal cavity; teeth are laid; the pancreas begins to produce insulin.
At the end of the 3rd month, the fetus measures 6.5 centimeters and weighs about 73 grams .

Things to remember in the 1st trimester of pregnancy

Most of the development of your unborn baby's nervous system occurs during the 1st trimester of pregnancy.

Learn more

• 
  3 month old baby movements
• 
  How to stop child support garnishments
• 
  What to expect each week of pregnancy
• 
  Fetus five weeks
• 
  Cerebral palsy caused by birth
• 
  Red spots on back of neck
• 
  Hungry all the time pregnant
• 
  Am i going to get pregnant
• 
  Swollen feet when waking up
• 
  Hunger pains pregnancy
• 
  Chicken pox symptoms for infants