burger-menu
Or Choose Category
End of Life
Life & the Law
Maternal & Public Health
Abortion
Fetal Tissue, Stem Cells & Bioethics
Fetal Development
Chemical Abortion
Trending Research
close-panel

Charlotte Lozier Institute

Phone: 202-223-8073
Fax: 571-312-0544

2776 S. Arlington Mill Dr.
#803
Arlington, VA 22206

Get Notifications

Sign up to receive email updates from Charlotte Lozier Institute.

close-panel

Become A Defender of Life

Your donation helps us continue to provide world-class research in defense of life.

DONATE

Charlotte Lozier Institute

Phone: 202-223-8073
Fax: 571-312-0544

2776 S. Arlington Mill Dr.
#803
Arlington, VA 22206

The
Voyage of Life
Weeks 1 and 2
Week 3
Week 4
Week 5
Week 6
Week 7
Week 8
Week 9
Week 10
Week 11
Week 12
Week 13
Week 14
Weeks 15 & 16
Weeks 17 & 18
Weeks 19 & 20
Weeks 21 & 22
Month 6
Month 7
Month 8
Month 9 and Birth

Weeks 17 & 18

Stress response and sensations

Human Prenatal Age
  • Post-conception week 15&16
  • 5 Months Pregnant
  • Gestational Weeks 17&18
Highlights

  • The fetus responds to a painful procedure with a stress response that includes recoiling and increasing circulating stress hormones in his bloodstream separate from any stress hormones in the mother’s bloodstream.1

  • The fetus begins storing energy as body fat. Fat deposits make the baby’s cheeks chubby.2

  • The corpus callosum, which connects the right and left sides of the brain, begins developing.3

Although the baby started moving at 7 ½ weeks gestation, the fetus has finally become big enough and strong enough for the mother to feel. A pregnant mother can usually feel her unborn child moving around 16 weeks if she has had a previous child, and 18 weeks if she has not. This is also known as quickening.4

In week 17 and 18, the mother may feel her unborn child moving. (Image Credit: Priests for Life)
The fetal stress response

Stress and pain responses in the unborn have been recorded from fetuses as young as 18 weeks gestation. When doctors used a needle to draw blood from a vein near the fetus’s liver, the fetus responded with “vigorous body and breathing movements” similar to recoiling. Furthermore, five minutes after the transfusion, large increases in stress hormones were observed in the fetus’s blood, but not the mother’s blood, showing that the fetus’s stress response was separate from the mother’s. Additionally, when a needle was inserted into the umbilical cord, which does not have pain receptors, the fetus did not respond with a large increase in circulating stress hormones. This shows that the hormones are released in response to the sensation of pain.5

Lung development

Additionally, the airways in the lungs keep developing. Cilia, which started to grow at 15 weeks, are now developing at a rapid pace.6 Cilia are tiny hair-like projections protruding from the cells that line the airway. Cilia catch debris and mucus and sweep it towards the throat, helping prevent infections in the lungs. The mature cells that line the airway will have about 200 cilia each.7

Airways in the lungs finish forming around 18 weeks,8 although the sites of gas exchange in the lungs, called alveoli, still need to develop and mature.

When does a baby start forming blood?

Although the baby has blood by week 6 when the heart starts beating, many of the complex cells in the blood, such as red and white blood cells form later and in different locations than they do in the adult. For example, around week 11, red blood cells start forming in the liver.9 At 17 weeks, fetal blood cells start forming in the bone marrow.10 Blood cells will form in the bone marrow for the rest of the baby’s life.

Dive Deeper
The Science of Fetal Pain
The old, uninformed notions that unborn and newborn babies cannot feel pain are refuted by a growing body of scientific evidence.
Read More
Brain Connections for Movement and Sensations
The brain assumes its adult shape around 5 months...
Read More
Back to The Voyage of Life
Sources
  1. Xenophon Giannakoulopoulos et al., “Human Fetal and Maternal Noradrenaline Responses to Invasive Procedures,” Pediatric Research 45, no. 4 (April 1999): 494–99, https://doi.org/10.1203/00006450-199904010-00007.
  2. C. M. Poissonnet, A. R. Burdi, and S. M. Garn, “The Chronology of Adipose Tissue Appearance and Distribution in the Human Fetus,” Early Human Development 10, no. 1–2 (September 1984): 1–11, https://doi.org/10.1016/0378-3782(84)90106-3.
  3. Keunen, Kristin, Serena J. Counsell, and Manon J. N. L. Benders. “The Emergence of Functional Architecture during Early Brain Development.” NeuroImage, Functional Architecture of the Brain, 160 (October 15, 2017): 2–14. https://doi.org/10.1016/j.neuroimage.2017.01.047.
  4. Mangesi, L., Hofmeyr, G. J., Smith, V., & Smyth, R. M. (2015). Fetal movement counting for assessment of fetal wellbeing. Cochrane Database of Systematic Reviews, (10).
  5. Giannakoulopoulos et al., “Human Fetal and Maternal Noradrenaline Responses to Invasive Procedures,” Pediatric Research 45, no. 4 (April 1999): 494–99, https://doi.org/10.1203/00006450-199904010-00007.
  6. J. W. DiFiore and J. M. Wilson, “Lung Development,” Seminars in Pediatric Surgery 3, no. 4 (November 1994): 221–32.
  7. Guyton, AC, and JE Hall. Textbook of Medical Physiology. 10th ed. Philadelphia: W.B. Saunders, 2000.
  8. J. W. DiFiore and J. M. Wilson, “Lung Development,” Seminars in Pediatric Surgery 3, no. 4 (November 1994): 221–32.
  9. Sadler, Thomas W. Medical Embyrology. 14th ed., 2019.
  10. K. C. Pringle, “A Reassessment of Pregnancy Staging,” Fetal Diagnosis and Therapy 3, no. 3 (1988): 173–84, https://doi.org/10.1159/000263352.
See Full Bibliography

All images and illustrations on The Voyage of Life were reviewed by credentialed scientists for accuracy.

Medical art animation was used to provide a schematic representation of fetal development, with some features, including timing, not to scale. The animation was chosen as an ethically uncompromised guide to fetal development. There are many real human images at each developmental age showing the most accurate fetal forms throughout development. A concerted effort was made to use images and material in which the human embryo or fetus did not undergo any known harm.

Page last updated on November 22, 2023