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

Month 8 to 9

Brain growth and lung maturation

Human Prenatal Age
  • PCW 30-33
    i
    Post-Conception Weeks
  • 8 Months Pregnant
  • Gestational Weeks 32-35
Highlights

  • At 30 weeks after conception, the fetus practices breathing almost 40% of the time.1

  • At 32 weeks after conception, the fetal heart pumps about 990 quarts of blood each day.2

  • By 32 weeks after conception, true alveoli start forming in the lungs. About 95% of the true alveoli develop after birth. Children keep growing true alveoli until age 8.3 

  • Although in boys, the testicles develop 12 weeks after conception, they remain in the abdomen until 33 weeks after conception. Then they descend into the scrotum.4 

The creation of synapses between neurons peaks 32 weeks after conception.5 Simultaneously, the fetus’s ability to recognize familiar songs and stories improves dramatically.6

40000
Synapses / Second
At their peak, neurons create 40,000 new synapses every second!7 After birth, many of these synapses will be eliminated as the brain supports the survival of neurons and synapses that efficiently transmit messages, while the unnecessary neurons and synapses are removed.8

This month, the brain develops many bumps and grooves, called gyri and sulci.9 These bumps and grooves increase the surface area of the brain, which is important because the cortex is only on the surface of the brain. By adding gyri and sulci all over, the brain can pack in more cortical neurons than it otherwise could. This explosive brain growth is accompanied by huge advances in fetal learning capabilities.

At this point, the baby makes a variety of facial expressions. His eyelids open and close, and his eyes move rapidly while he sleeps. (Image Credit: Science Source)
When does the fetus start to learn?

Although the fetus is actively sensing his world for most of the pregnancy, he only starts to show measurable signs of recognition around 30 weeks after conception.10 Specifically, researchers can measure recognition in utero by examining changes in fetal heartrate. In the third trimester, the fetus usually responds to non-startling sounds with a mild deceleration in heartrate. The fetus will respond to a familiar sound with a larger heartrate deceleration than she will respond to an unfamiliar sound. When mothers read a rhyme aloud daily, it took 26-week post-conception fetuses about 5 weeks to become familiar with the rhyme. However, it only took 30-week post-conception babies 2 weeks to become familiar with the rhyme, showing that sound recognition dramatically improves between 26 and 30 weeks after conception.11

This premature baby benefits from skin time. The mother’s body helps regulate his temperature and reduce stress hormones. Over 98% of babies born in this month survive.12 (Image Credit: Sathishsugavanam27, 29 January 2019)

At birth, newborns prefer looking at faces compared to upside-down faces or other images. Scientists also wondered whether postnatal experience was important for this preference. To answer this question, one research group decided to project patterned light from outside the mother into the womb. Red lasers projected three dots into the womb – one set of dots that looked like a face, with eyes and a mouth, and another set upside-down. Amazingly, at 32 weeks after conception, the fetuses turned their heads toward the face-like lights projected through the uterine wall, and turned less when the dots were upside-down.13 This shows that not only can the fetus see and respond to visual information from outside the womb, the fetus also prefers looking at face-like stimuli.

By this point, the fetus also grasps objects that come near her hands. In fact, as early as 25 weeks after conception, the fetus can hold her own body weight momentarily by grasping.14

Dive Deeper
Fetal Taste and Maternal Diet
By 26 weeks, the fetus can distinguish between different smells in the amniotic fluid...
Read More
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Sources
  1. de Vries, J. I. de, G. H. Visser, and H. F. Prechtl. “The Emergence of Fetal Behaviour. II. Quantitative Aspects.” Early Human Development 12, no. 2 (November 1985): 99–120. https://doi.org/10.1016/0378-3782(85)90174-4.
  2. 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.
  3. Moore, Keith, TVN Persaud, and Mark G. Torchia. The Developing Human, Clinically Oriented Embryology. 10th ed. Philadelphia: Elsevier, 2016.
  4. Sadler, Thomas W. Medical Embyrology. 14th ed., 2019.
  5. Marsh, Rachel, Andrew J. Gerber, and Bradley S. Peterson. “Neuroimaging Studies of Normal Brain Development and Their Relevance for Understanding Childhood Neuropsychiatric Disorders.” Journal of the American Academy of Child & Adolescent Psychiatry 47, no. 11 (November 1, 2008): 1233–51. https://doi.org/10.1097/CHI.0b013e318185e703.
  6. Charlene Krueger and Cynthia Garvan, “Emergence and Retention of Learning in Early Fetal Development,” Infant Behavior and Development 37, no. 2 (May 1, 2014): 162–73, https://doi.org/10.1016/j.infbeh.2013.12.007.
  7. Marsh, Rachel, Andrew J. Gerber, and Bradley S. Peterson. “Neuroimaging Studies of Normal Brain Development and Their Relevance for Understanding Childhood Neuropsychiatric Disorders.” Journal of the American Academy of Child & Adolescent Psychiatry 47, no. 11 (November 1, 2008): 1233–51. https://doi.org/10.1097/CHI.0b013e318185e703.
  8. Susan L Andersen, “Trajectories of Brain Development: Point of Vulnerability or Window of Opportunity?,” Neuroscience & Biobehavioral Reviews, Brain Development, Sex Differences and Stress: Implications for Psychopathology, 27, no. 1 (January 1, 2003): 3–18, https://doi.org/10.1016/S0149-7634(03)00005-8.
  9. Catherine Garel et al., “Fetal Cerebral Cortex: Normal Gestational Landmarks Identified Using Prenatal MR Imaging,” American Journal of Neuroradiology 22, no. 1 (January 1, 2001): 184–89.
  10. Charlene Krueger and Cynthia Garvan, “Emergence and Retention of Learning in Early Fetal Development,” Infant Behavior and Development 37, no. 2 (May 1, 2014): 162–73, https://doi.org/10.1016/j.infbeh.2013.12.007.
  11. Charlene Krueger and Cynthia Garvan, “Emergence and Retention of Learning in Early Fetal Development,” Infant Behavior and Development 37, no. 2 (May 1, 2014): 162–73, https://doi.org/10.1016/j.infbeh.2013.12.007.
  12. Emily Oster, Expecting Better: How to Fight the Pregnancy Establishment with Facts (London: Orion, 2013).
  13. Vincent M. Reid et al., “The Human Fetus Preferentially Engages with Face-like Visual Stimuli,” Current Biology 27, no. 12 (June 19, 2017): 1825-1828.e3, https://doi.org/10.1016/j.cub.2017.05.044.
  14. Tryphena Humphrey, “Some Correlations between the Appearance of Human Fetal Reflexes and the Development of the Nervous System,” in Progress in Brain Research, ed. Dominick P. Purpura and J. P. Schadé, vol. 4, Growth and Maturation of the Brain (Elsevier, 1964), 93–135, https://doi.org/10.1016/S0079-6123(08)61273-X.
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 August 29, 2022
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