Charlotte Lozier Institute

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

2776 S. Arlington Mill Dr.
Arlington, VA 22206

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Weeks 21 & 22

Preparing for life outside the womb

Human Prenatal Age
  • Post-conception week 19&20
  • 5-6 Months Pregnant
  • Gestational Weeks 21&22
  • By 22 weeks the inner ear has developed. The baby moves after hearing a loud, low-pitched sound, such as her father’s voice.1

  • The left and right sides of the brain show differences as early as 22 weeks.2

  • The fetus responds to taste, temperature, pain, pressure, movement, and light with changes in heart rate and movement patterns.3

Between the beginning and the end of the fifth month, the fetus prepares for life outside of the womb. Multiple babies born after 21 weeks and 1 day gestation have survived.4 Many American hospitals have started routinely offering resuscitation and active care for infants born at 22 and 23 weeks gestation.

Starting in the fifth month, the fetus’s movements and breathing follows a daily cycle, called a circadian rhythm.5 Interestingly, fetal activity, especially breathing movements, increases about two hours after the mother eats, and then starts to decrease.6 The fetal heart rate follows a daily pattern as well.7

By examining continuous ultrasounds of fetuses between 20 and 40 weeks, researchers found that the fetus shows periods of wakefulness, and that she sleeps in cycles of about 45 minutes, or half the length of an adult sleep cycle.8

In females, the number of future eggs in the ovary peaks around 7 million at 21 weeks. After this, the ovary essentially stops creating oogonia, and about 5 million of these cells die before birth. The remaining oogonia produce several thousand primary oocytes, or egg cells.9

Every detail of the human face comes together with flawless precision, following the genetic blueprint laid forth in the zygote. (Image Credit: Priests for Life)
Dive Deeper
More and more premature babies born after 21 weeks gestation survive as...