Summary:
For further details, please refer to the complete fact sheet.
Pregnancy, also referred to as gestation, spans 40 weeks and commences from the onset of your last menstrual cycle. It is segmented into three trimesters.
The gender and inherited traits of the baby are determined at conception.
Estimating your expected due date is a general guideline; infants typically arrive when they are prepared.
The duration of pregnancy can differ among individuals. Babies considered ‘full term’ may be born anywhere between 37 to 42 weeks, while some may arrive prematurely.
An unborn baby typically spends approximately 38 weeks in the womb, although the average duration of pregnancy (gestation) is counted as 40 weeks.
This discrepancy arises because pregnancy is measured from the first day of the woman’s last menstrual period, rather than the date of conception, which typically occurs about 2 weeks later.
Furthermore, pregnancy is generally divided into three distinct stages known as trimesters, each lasting approximately three months:
- The first trimester spans from conception to 12 weeks.
- The second trimester encompasses weeks 13 to 27.
- The third trimester extends from weeks 28 to 40.
It is important to note that the length of pregnancy can vary among women. Babies are considered ‘full term’ if they are born anywhere between 37 to 42 weeks.
During the first trimester of pregnancy, which spans from conception to 12 weeks, there are various symptoms and signs that may indicate early pregnancy:
- Missed periods
- Nausea and vomiting, often referred to as morning sickness
- Changes in the breasts
- Fatigue
- Increased frequency of urination
If you are experiencing any of these symptoms and suspect that you might be pregnant, it is advisable to take a pregnancy test.
In cases where the pregnancy was unintended, it is crucial to undergo a pregnancy test as soon as possible. Confirming the pregnancy early enables you to access care promptly and provides you with a wider range of options.
Miscarriage is common during the first trimester, with approximately 1 in 4 pregnancies ending in miscarriage. The majority of spontaneous miscarriages (75 to 80 percent) occur within the first 12 weeks of pregnancy. It’s worth noting that many miscarriages go unreported or unnoticed, especially when they happen very early in the pregnancy.
Conception occurs when the woman’s ovum (egg) is fertilized by the man’s sperm. It is at this moment that the gender and inherited characteristics of the baby are determined.
Pregnancy Week 1:
During this initial week, you are experiencing your menstrual period. Despite not having conceived yet, this week is considered part of your 40-week pregnancy, as your expected due date (EDD) is calculated from the first day of your last period. If you are aware of the date of your last period, you can utilize a gestation calculator to determine your due date.
Pregnancy Week 2:
Fertilization of your egg by sperm, known as conception, typically occurs towards the end of this week.
Pregnancy Week 3:
Approximately thirty hours post-conception, the fertilized cell divides into two. Three days later, it further divides into 16 cells. Within two more days, the fertilized egg, now called a zygote, moves from the fallopian tube to the uterus (womb). By the seventh day post-conception, the zygote implants itself into the thick uterine lining (endometrium), now termed a blastocyst.
Pregnancy Week 4:
At this stage, the developing baby is smaller than a grain of rice. The rapidly dividing cells are beginning to form various body systems, including the digestive system.
Pregnancy Week 5:
The emerging neural tube will eventually develop into the central nervous system, comprising the brain and spinal cord.
Pregnancy Week 6:
At this stage, the developing baby is referred to as an embryo, measuring approximately 3 mm in length. It begins secreting specific hormones that prevent the mother from experiencing menstrual periods.
Pregnancy Week 7:
The baby’s heart starts beating, and the embryo establishes its placenta and amniotic sac. The placenta embeds itself into the uterine wall to access oxygen and nutrients from the mother’s bloodstream.
Pregnancy Week 8:
The embryo grows to about 1.3 cm, with a rapidly developing spinal cord resembling a tail. The head appears disproportionately large.
Pregnancy Week 9:
Formation of the eyes, mouth, and tongue begins, while tiny muscles allow the embryo to start moving. The embryo’s liver starts producing blood cells.
Pregnancy Week 10:
The embryo transitions into a fetus, measuring approximately 2.5 cm. All major organs are formed, and nubs or paddles evolve into distinct fingers and toes. Brain activity with brain waves is detected.
Pregnancy Week 11:
Teeth buds start forming inside the gums, and the baby’s heart continues to develop.
Pregnancy Week 12:
Fingers and toes become recognizable, although still connected by webs of skin. The first-trimester combined screening test, which includes a maternal blood test and ultrasound of the baby, can be conducted around this time. This test assesses for trisomy 18 (Edward syndrome) and trisomy 21 (Down syndrome).
Second Trimester of Pregnancy – Weeks 13 to 27:
The second trimester typically spans from weeks 13 to 27 of pregnancy. During this period, many women experience relief from morning sickness and may notice an increase in energy levels.
By this time, your pregnancy may become more apparent, and you might have gained some weight. While steady weight gain is normal and essential for both your health and the baby’s, it’s important to maintain a balanced diet and engage in regular exercise to avoid excessive weight gain.
Gestational diabetes screenings typically occur around weeks 24 to 28, although it may manifest earlier.
Pregnancy Week 13:
The fetus becomes more active, capable of swimming vigorously, and measures over 7 cm in length.
Pregnancy Week 14:
Eyelids cover the fully developed eyes, and the baby, now equipped with vocal cords, can silently cry. It may even start sucking its thumb, while nails begin to form on the fingers and toes.
Pregnancy Week 16:
The fetus reaches approximately 14 cm in length, with the appearance of eyelashes, eyebrows, and taste buds on the tongue. Maternal serum screening for the second trimester is offered if not done during the first trimester (see week 12).
Pregnancy Weeks 18-20:
An ultrasound is conducted to assess fetal morphology, including checking for structural abnormalities, placental position, and the presence of multiple pregnancies. Additionally, fetal hiccups may be observed.
Pregnancy Week 20:
Measuring around 21 cm, the fetus’s ears are fully functional, enabling it to perceive muffled sounds from the external environment. Fingerprints begin to form, and gender can often be distinguished through ultrasound imaging.
Pregnancy Week 24:
At this stage, the fetus measures approximately 33 cm and gains further development. Eyelids, previously fused, now separate into upper and lower lids, allowing the baby to open and close its eyes. The skin is covered in fine hair (lanugo) and protected by a layer of waxy secretion (vernix), while the baby initiates breathing movements with its lungs.
Third Trimester of Pregnancy – Weeks 28 to 40:
During the third trimester, your baby undergoes rapid growth, and you may experience increased fatigue. As your baby develops, you will notice changes in your body. In the later weeks, your baby will descend into your pelvis in preparation for birth.
It is common to feel anxious, along with experiencing back pain, shortness of breath, and sleep disturbances as labor approaches. While preeclampsia can occur at any point during the latter half of pregnancy, the risk is higher during this stage.
Pregnancy Week 28:
Your baby now weighs around 1 kg (1,000 g) or 2 lb 2 oz and measures approximately 25 cm (10 inches) from crown to rump, with a total length of around 37 cm. The body has caught up with the large head, and the baby appears more proportionate.
Pregnancy Week 32:
The baby spends most of its time asleep, with strong and coordinated movements. It likely assumes the head-down position in preparation for birth.
Pregnancy Week 36:
At around 46 cm in length, the baby has likely nestled its head into the mother’s pelvis in readiness for birth. If born at this stage, the baby’s chances of survival are excellent, and lung development progresses rapidly over the ensuing weeks.
Pregnancy Week 40:
Measuring approximately 51 cm, the baby is fully developed and ready for birth. The onset of labor is influenced by a combination of physical, hormonal, and emotional factors between the mother and baby.