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This week marks a developmental milestone for the baby
Pregnancy

This week marks a developmental milestone for the baby

2 min readWeek 20
Key takeaways
2 min
  • Monitor your baby's organ development as all internal organs are now formed and functioning at this developmental stage.
  • Expect to feel baby movements more clearly if carrying twins, as cramped space makes movements more noticeable than single pregnancies.
  • Schedule detailed ultrasounds to observe baby's head contours, heart chambers, stomach, and limb development during this milestone week.
  • Track nervous system development as your baby's brain forms grooves and the endocrine system reaches full capacity.
  • Prepare for increased fetal activity as your baby can now see, hear, swallow, and suck independently.

During this developmental milestone week, all baby's internal organs are formed and functioning. Baby can see, hear, swallow, and suck while the nervous system continues producing neurons and the endocrine system works at full capacity regulating growth and development.

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This week marks a developmental milestone for the baby

All of the baby’s internal organs are formed and more or less ready to carry out their functions [1]. The baby can see, hear, swallow, and suck.

The baby’s nervous system continues to produce neurons and improve interneuron connections. Their cerebral cortex forms grooves and convolutions, and the differentiation of the cortex’s functional divisions continues. The endocrine system, which produces hormones for everything from metabolism and sleep to growth regulation and sexual function, works at full capacity, playing a role in the functioning of all of the baby’s organs and systems.

At this time, not all mothers can feel their baby’s movements [1]. But if your partner already notices them, they will soon become more pronounced.

If your partner is expecting twins

The babies are starting to get a little cramped, so your partner can probably feel their movements quite clearly, while mothers carrying single pregnancies haven’t felt anything at all.

What we can see on an ultrasound

The image shows a baby during the current week of pregnancy. The baby is lying on their left side, facing the screen.

A clearly defined contour of the head allows us to examine in detail the frontal bones, paired nasal bones, and chin. The mouth is a narrow strip that divides the upper and lower jaws.

This week marks a developmental milestone for the baby - This week marks a developmental milestone for the baby
  1. placenta

  2. hands

  3. head

In the next picture, the heart is clearly divided into the atria and ventricles. Above the spine, in the lower part of the image, the aorta is barely noticeable.

In this image, the stomach looks like a dark oval. Deep in the amniotic fluid, you can see the baby’s hand.

This week marks a developmental milestone for the baby - This week marks a developmental milestone for the baby
  1. stomach

  2. hand

  3. head

  4. heart

The next image shows twins. One of them sits in the foreground, while the other lies slightly higher.

You can see the tiny feet and toes of the baby in the foreground. The other baby’s limbs are partially visible.

This week marks a developmental milestone for the baby - This week marks a developmental milestone for the baby
  1. legs

  2. head


  1. Brewer S. The Pregnant Body Book. Dorling Kindersley Publishing Staff, 2012, p. 136, 139. 

Frequently asked questions

Most mothers feel baby movements between 16-25 weeks of pregnancy. If you're carrying twins, you'll likely feel movements earlier and more clearly due to less space in the uterus.

When baby's organs are fully formed, they can see, hear, swallow, and suck. Their nervous system continues developing neurons and their endocrine system works at full capacity regulating growth and metabolism.

During milestone weeks, ultrasounds clearly show baby's head contours, facial features, heart chambers divided into atria and ventricles, stomach, and developing limbs. Twins may appear more cramped but both babies' features are visible.

Baby's cerebral cortex forms grooves and convolutions while the nervous system produces neurons and improves connections. Functional divisions of the brain cortex continue differentiating throughout this developmental period.

Medical Disclaimer

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or qualified health provider with any questions you may have regarding a medical condition.

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Medically reviewed content

Reviewed by healthcare professionals · Updated September 3, 2024

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