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

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

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Charlotte Lozier Institute

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

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

The
Voyage of Life
Preparing for Pregnancy
Week 0 to 1
Week 1 to 2
Week 2 to 3
Week 3 to 4
Week 4 to 5
Week 5 to 6
Week 6 to 7
Week 7 to 8
Week 8 to 9
Week 9 to 10
Week 10 to 11
Week 11 to 12
Weeks 13 & 14
Weeks 15 & 16
Weeks 17 & 18
Weeks 19 & 20
Month 6 to 7
Month 7 to 8
Month 8 to 9
Month 9 to Birth

Weeks 13 & 14

Sensory systems and sensations

Human Prenatal Age
  • PCW 13&14
    i
    Post-Conception Weeks
  • 4 Months Pregnant
  • Gestational Weeks 15&16
Highlights

  • Eyebrows have formed.1 

  • The fetal heart has already beat approximately 15,800,000 times.2

  • The stomach lining reaches its mature structure and secretes digestive enzymes into swallowed amniotic fluid.3

  • More of the preborn baby’s skeleton hardens from cartilage into bone. If a doctor took an X-ray this week, the fetus’s skeleton would be visible.4

  • The preborn baby’s circulatory system pumps about 26 quarts of blood per day at 13 weeks after conception. This is like 6 and 1/2 gallons of milk. For comparison, an adult heart pumps 6,000 quarts of blood each day, which would likely fill a small hot tub.5

At 13 weeks after conception, the evidence points to the fetus being able to experience pain. While touch receptors cover almost all of the body, pain receptors develop later than regular touch receptors. Pain receptors develop from 8 to 15 weeks after conception, starting in the hands and the area around the mouth.6 Two neurotransmitters specific to pain processing, substance P and enkephalins, have already appeared at 8-10 weeks after conception and 10-12 weeks after conception, respectively. Furthermore, nerves connecting the primitive pain receptors with the spinal cord and thalamus can be observed as early as 13 weeks after conception.7 While the cortex may not be fully developed, a number of brain structures that process pain activity including the brainstem, insula, and thalamus, are sufficiently mature to process pain at 13 weeks after conception.8 Taken together, the evidence suggests that a fetus can now feel pain.

This fetus could taste the amniotic fluid within the amniotic sac. When the fluid was sweet, he swallowed more than when it was bitter. (Image Credit: Priests for Life)
Purposeful movements

Thirteen weeks after conception, the fetus’s entire body responds to light touch with the exception of parts of the back, buttocks, and thighs.9 The fetus also starts moving each finger separately, and often sucks his or her thumb. By 14 weeks after conception, the unborn child starts grasping objects.10 Interestingly, boys and girls move differently in the womb. In fact, girls open and close their mouths more often than boys do!11 Until this point, the fetus has been mostly stoic. Now the preborn child produces complex facial expressions. According to some research groups, the fetus can even smile!12

By 12 weeks after conception, the fetus displays goal-directed movements. Before this age, the fetal movements were jerky and ballistic, but now the hands slow down as they approach their target. These intentional fetal movements show that the fetus is conscious and aware of his environment. Most of the slower, goal-directed movements were directed at the fetus’ face. However, if the fetus has a twin, he or she will move more slowly when reaching towards the twin’s face as well.13

15 Facts at 15 Weeks
Read the Report
Fetal senses

Many sensory systems start processing rudimentary information in weeks 13 & 14. The olfactory bulb, which processes smells, develops its layered structure at 12 weeks after conception.14 Tastebuds start clustering in functional taste pores and connecting to cranial nerves 12-13 weeks after conception, making it likely that the fetus tastes the amniotic fluid by 13 weeks after conception.15 In fact, 13-14 weeks after conception, the fetus will swallow more amniotic fluid if the amniotic fluid tastes sweet, and less if it tastes bitter.16 Each sensory system is partially developed by 13 weeks after conception.

Dive Deeper
Brain Connections for Movement and Sensations
The brain assumes its adult shape around 5 months after conception...
Read More
Back to The Voyage of Life
Sources
  1. Sadler, Thomas W. Medical Embyrology. 14th ed., 2019.
  2. EHD: Appendix. Appendix
  3. Montgomery, Robert K., Andrew E. Mulberg, and Richard J. Grand. “Development of the Human Gastrointestinal Tract: Twenty Years of Progress.” Gastroenterology 116, no. 3 (March 1, 1999): 702–31. https://doi.org/10.1016/S0016-5085(99)70193-9.
  4. Moore, Keith, TVN Persaud, and Mark G. Torchia. The Developing Human, Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016.
  5. Molina, F. S., C. Faro, A. Sotiriadis, T. Dagklis, and K. H. Nicolaides. “Heart Stroke Volume and Cardiac Output by Four-Dimensional Ultrasound in Normal Fetuses.” Ultrasound in Obstetrics & Gynecology: The Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology 32, no. 2 (August 2008): 181–87. https://doi.org/10.1002/uog.5374.
  6. Bellieni, Carlo V. “Analgesia for Fetal Pain during Prenatal Surgery: 10 Years of Progress.” Pediatric Research, September 24, 2020, 1–7. https://doi.org/10.1038/s41390-020-01170-2.; Terenghi, G., Sundaresan, M., Moscoso, G. & Polak, J. M. Neuropeptides and a neuronal marker in cutaneous innervation during human foetal development. J. Comp. Neurol. 328, 595–603 (1993).
  7. Bellieni, Carlo V. “Analgesia for Fetal Pain during Prenatal Surgery: 10 Years of Progress.” Pediatric Research, September 24, 2020, 1–7. https://doi.org/10.1038/s41390-020-01170-2.; Kostovic, I. & Judas, M. Transient patterns of cortical lamination during prenatal life: do they have implications for treatment? Neurosci. Biobehav. Rev. 31, 1157–1168 (2007).
  8. Sekulic, S., Gebauer-Bukurov, K., Cvijanovic, M., Kopitovic, A., Ilic, D., Petrovic, D., ... & Topalidou, A. (2016). Appearance of fetal pain could be associated with maturation of the mesodiencephalic structures. Journal of Pain Research, 9, 1031. https://doi.org/10.2147/JPR.S117959.;Derbyshire, S. and Bockmann, J. “Reconsidering Fetal Pain,” Journal of Medical Ethics 46, no. 1 (January 2020): 3–6, https://doi.org/10.1136/medethics-2019-105701.
  9. Humphrey, “Some Correlations between the Appearance of Human Fetal Reflexes and the Development of the Nervous System”; Jean-Pierre Lecanuet and Benoist Schaal, “Fetal Sensory Competencies,” European Journal of Obstetrics & Gynecology and Reproductive Biology 68 (September 1996): 1–23, https://doi.org/10.1016/0301-2115(96)02509-2.
  10. Humphrey, Tryphena. “Some Correlations between the Appearance of Human Fetal Reflexes and the Development of the Nervous System.” In Progress in Brain Research, edited by Dominick P. Purpura and J. P. Schadé, 4:93–135. Growth and Maturation of the Brain. Elsevier, 1964. https://doi.org/10.1016/S0079-6123(08)61273-X.
  11. P. G. Hepper, E. A. Shannon, and J. C. Dornan, “Sex Differences in Fetal Mouth Movements,” Lancet (London, England) 350, no. 9094 (December 20, 1997): 1820, https://doi.org/10.1016/S0140-6736(05)63635-5.
  12. A. Piontelli. Development of Normal Fetal Movements: The First 25 Weeks of Gestation. Chapter 7-Facial Expressions. Springer, 2010.; H B Valman and J F Pearson, “What the Fetus Feels.,” British Medical Journal 280, no. 6209 (1980): 233–34, https://doi.org/10.1136/bmj.280.6209.233.
  13. Castiello, Umberto, Cristina Becchio, Stefania Zoia, Cristian Nelini, Luisa Sartori, Laura Blason, Giuseppina D’Ottavio, Maria Bulgheroni, and Vittorio Gallese. “Wired to be social: the ontogeny of human interaction.” PloS one 5, no. 10 (2010). https://doi.org/10.1371/journal.pone.0013199.
  14. Harvey B. Sarnat and Laura Flores-Sarnat, “Development of the Human Olfactory System.,” Handbook of Clinical Neurology 164 (2019): 29–45, https://doi.org/10.1016/B978-0-444-63855-7.00003-4.
  15. Witt, M., and K. Reutter. “Embryonic and Early Fetal Development of Human Taste Buds: A Transmission Electron Microscopical Study.” The Anatomical Record 246, no. 4 (December 1996): 507–23. https://doi.org/10.1002/(SICI)1097-0185(199612)246:4<507::AID-AR10>3.0.CO;2-S.
  16. Liley, A. W. “The Foetus as a Personality.” The Australian and New Zealand Journal of Psychiatry 6, no. 2 (June 1972): 99–105. https://doi.org/10.3109/00048677209159688; P. G. Hepper, “Unravelling Our Beginnings | The Psychologist,” 2005, https://thepsychologist.bps.org.uk/volume-18/edition-8/unravelling-our-beginnings.
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 February 16, 2023