During week 12 of pregnancy, the organ systems of the fetus have practically formed and will continue to grow and start functioning as pregnancy progresses.

As with earlier weeks, a fetus grows rapidly and makes huge developmental strides in week 12. In fact, between weeks 8 and 12, your child will have almost doubled in size.

This article provides a summary of the 12th week of pregnancy, what to expect, how to maintain employment while pregnant, and insights into how your baby is developing.

Take a look at the other articles in the series:

First trimester: fertilization, implantation, week 5, week 6, week 7, week 8, week 9, week 10, week 11.

Second trimester: week 13, week 14, week 15, week 16, week 17, week 18, week 19, week 20, week 21, week 22, week 23, week 24, week 25, week 26.

Fast facts on pregnancy at 12 weeks

  • At 12 weeks of pregnancy, a woman might experience dizziness, bloating, and an increased sex drive.
  • Workplace discrimination by employers against women who are pregnant is illegal.
  • Consider reducing work hours if needed.
  • The fetus is roughly the size of a plum.
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At 12 weeks pregnant, the womb is rapidly growing to accommodate the growing fetus.

At this stage of your pregnancy, you may continue to experience pregnancy symptoms in the body.

These can include:

  • dizziness
  • changes in sex drive
  • frequent need to urinate
  • fatigue
  • excessive saliva
  • bloating or gas
  • a heightened sense of smell
  • increase in vaginal discharge
  • occasional headaches

The pregnancy might or might not be visibly obvious at this stage, but the womb is growing to accommodate the rapidly expanding fetus. During this time of your pregnancy, the uterus is the size of a large grapefruit.

A woman who is pregnant may start feeling the need to wear looser fitting clothes or even maternity clothes around week 12.

There is a higher risk of a urinary tract infection (UTI) during pregnancy. If symptoms suggest an infection, speak to a healthcare provider about treatment.

Expecting the arrival of an infant is a huge change that carries high levels of pressure and preparation. If a woman is in employment while pregnant, there is often a fear of being stigmatized by an employer or even fired as a result of the pregnancy.

There have been laws in place since the Pregnancy Discrimination Act of 1978 to protect women who are pregnant and attending the workplace. This law states that a company may not refuse to hire or fire a woman as a result of pregnancy.

A woman working through her pregnancy is also protected from:

  • losing seniority in the company
  • losing retirement benefits and pensions
  • losing employment as a result of having an abortion

The Family and Medical Leave Act (1993) ensured that workers who are pregnant receive a guaranteed 12 weeks of unpaid maternity leave without losing employment.

While laws differ across the world, many industrialized nations have safeguards in place to protect women who become pregnant during employment.

However, despite these safeguards, some employers discriminate based on pregnancy status. The US Equal Employment Opportunities Commission (EEOC) conducted a study in 2005 that showed a 65 percent increase in the number of complaints against employers that related to pregnancy between 1992 and 2007.

If you feel as if you are receiving unfair treatment or being unjustly dismissed due to a recent pregnancy, contact the EEOC using this webpage.

Is it safe to work while pregnant?

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Working while pregnant is safe and legally protected.

One common stigma is that women should avoid the workplace while pregnant, as the sustained activity levels could be harmful to the mother and infant. However, this is not the case in jobs that do not feature large amounts of manual labor.

If a role requires long periods of standing up or heavy lifting, your employer should reassign responsibilities. Studies have shown that lifting did not generally show a significant impact on childbirth complications.

Working over 40 hours per week has the greatest significance in affecting a modest drop in birth weight but not spontaneous abortion.

Another risk is exposure to chemicals in the workplace that could harm mother and infant, such as second-hand tobacco smoke and carbon monoxide. However, studies into second-hand tobacco smoke exposure specifically at work have shown that the amount experienced is below a harmful threshold.

More research is required on the effect of industrial toxins on childbirth and developmental complications.

Women working in childcare that become pregnant need to be wary of contracting cytomegalovirus, as this is carried in the saliva and skin of children under 30 months old and can cause congenital abnormalities.

Some women who are pregnant decide to apply themselves harder at work during pregnancy to combat the stigma around pregnancy in the workplace, refusing time off and taking on extra hours or responsibilities to “prove” that pregnancy has not made them lazy or uncommitted.

However, this can add stress to the pregnancy and increase the risk of complications.

It is the employer’s responsibility to make an individual feel supported during pregnancy and accommodate the changes necessary to keep the environment safe for mother and child.

Week 12 of pregnancy means making adjustments to accommodate the pregnancy into everyday living and making some of the first full checks on the developing fetus.

Occupational steps

Here are some simple steps that will make continuing to work during pregnancy more comfortable:

  • Avoid standing for long periods, and sit down more often.
  • Always have a water bottle with you.
  • Break frequently for rest, urination, or eating.
  • Do not lift heavy objects without assistance.
  • Reduce the length of your working day.
  • Take time off to prepare for and recuperate from birth.

Make sure your employer knows about the pregnancy and takes the relevant steps to support these measures.

Combined first-trimester screening

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Ultrasound scans can provide a picture of fetal health.

Ultrasound scans can create a picture of the fetus and surrounding organs using sound waves.

Between week 11 and week 13, it will likely be time for two of the first ultrasound scans of the pregnancy. These are a dating scan, designed to provide an estimate of the due date, and a nuchal translucency scan, to assess the risk of chromosomal anomalies, such as Down syndrome.

A blood test may also be requested to assess the risk of abnormalities. If the results come back positive, it does not confirm the presence of Down syndrome or a similar condition. However, it does recommend further diagnostics to rule out genetic disorders.

Your baby is now roughly the size of a plum, measuring approximately 2.5 inches in length and weighing around an ounce.

The head of the fetus is around one half of the length from crown to rump and rests upon its neck rather than its shoulders.

Other developments that are underway include:

  • Head and neck: The head is now half of the size of the body, and the salivary glands start functioning.
  • Heartbeat: The heartbeat can now be heard with an external Doppler scan.
  • Chest: The lungs continue to mature, and amniotic fluid is now inhaled and exhaled.
  • Abdomen: The abdominal organs including the spleen, intestines, and liver are now formed.
  • Pelvis: The sex organs are now formed.
  • Limbs: The arms are now proportional and have increasingly functional hands, although the legs remain short.
  • Skin: The muscles and nervous system are maturing.
  • Other changes: The thyroid and pancreas glands are making hormones.

You will soon find that many lifestyle modifications need to be made during pregnancy and after delivery.

General health

Maintaining peak physical health is essential to both your wellbeing and that of the fetus.

Avoid alcohol, tobacco, and narcotic substances during pregnancy, and discuss any ongoing medications with your doctor.

Eat a healthy diet and be sure to take any necessary nutritional supplements recommended by your doctor during pregnancy. Regular exercise can also help maintain health during this crucial time.

Discuss your current exercise regimen or any regimen you have planned to make sure it is safe.


Using permanent hair color is not recommended during the first 12 weeks of pregnancy. Consider using semi-permanent dye as an alternative.

This article is part of a series exploring the development of a fetus at different stages of pregnancy and the effect it will have on the body.