Pregnancy Facts

Pregnancy is a miraculous process!  Here are a few facts to consider:

  • Pregnancy in humans normally lasts approximately 38 weeks as measured from the time of fertilization, or conception, until birth. 1
  • Biologically speaking, “human development begins at fertilization,” with the union of the male and female reproductive cells. 2
  • The heart begins beating 3 weeks and one day following fertilization. 3
  • Between 3 and 4 weeks, the body plan emerges as the brain, spinal cord, and heart of the embryo are easily identified. 4
  • The embryo begins to make spontaneous and reflexive movements 5 1/2 to 6 weeks after fertilization. Prenatal movement is necessary to promote normal bone and neuromuscular development. 5
  • Electrical activity of the embryo’s heart recorded at 7 1/2 weeks reveals a wave pattern similar to the adult’s. 6
  • By 7 1/2 weeks fingers are separate and toes are joined only at the bases. 7
  • During the embryonic period, the human embryo grows from a single cell into the nearly one billion cells which form over 4,000 distinct anatomic structures. 8
  • The 8-week embryo possesses more than 90% of the structures found in adults. 9
  • The 9-week fetus can grasp an object, move the head forward and back, open and close the jaw, move the tongue, sigh, and stretch. 10
  • By 9 weeks after fertilization, nerve receptors in the face, the palms of the hands, and the soles of the feet can sense light touch. 11
  • Between 9 and 10 weeks body weight increases by over 75%. 12
  • Fat deposits begin to fill out the cheeks by 14 weeks. 13
  • By 20 weeks the cochlea, which is the organ of hearing, has reached adult size within the fully developed inner ear. From now on, the fetus will respond to a growing range of sounds. 14
  • The heart of the developing human beats approximately 54 million times before birth.
  • Bone formation is underway in most bones by 10 weeks. 15

  • Footnotes

    All Facts Drawn From The Endowment For Human Development (EHD.org) – Improving lifelong health one pregnancy at a time.

    1. Cunningham FG et al., 2001, 226; Spraycar, 1995, 377 & 637; O’Rahilly and Muller, 1987, 9; O’Rahilly and Muller, 2001, 92.

    2. O’Rahilly and Muller, 2001, 8; Moore and Persaud, 2003, 16; “Biologically speaking, human development begins at fertilization.” O’Rahilly and Muller, 1987, 9; Carlson, 2004, 3.

    3. Campbell, 2004, 14; Wisser and Dirschedl, 1994, 108; O’Rahilly and Muller, 1987, 99; Navaratnam, 1991, 147-148; Kurjak and Kos, 1994, 439; van Heeswijk et al., 1990, 151; Gittenger-de Groot et al., 2000, 17; Gilbert-Barness and Debich-Spicer, 1997, 650; Gardner and O’Rahilly, 1976, 583; de Vries and Saunders, 1962, 96; Carlson, 2004, 117 & 430.

    4. Moore and Persaud, 2003, 78-79.

    5. Birnholz et al., 1978, 539; Hogg, 1941, 373; Sorokin and Dierker, 1982, 723 & 726; O’Rahilly and Muller, 1999a, 336; Natsuyama, 1991, 13; Visser et al., 1992, 175-176; Kurjak and Kos, 1994, 48; Humphrey and Hooker, 1961, 147; Humphrey and Hooker, 1959, 76; Humphrey, 1970, 12; Humphrey, 1964, 99; de Vries et al., 1982, 301 & 304; Liley, 1972, 101.

    6. Gardner and O’Rahilly, 1976, 571; Straus et al., 1961, 446.

    7. Moore and Persaud, 2003, 85.

    8. Pringle, 1988, 176; O’Rahilly and Muller, 2001, 87.

    9. O’Rahilly and Muller, 2001, 87.

    10. Robinson and Tizard, 1966, 52; de Vries et al., 1982, 311; de Vries et al., 1982, 305-307; Valman and Pearson, 1980, 234.

    11. Humphrey, 1964, 96; Humphrey and Hooker, 1959, 77-78; Reinis and Goldman, 1980, 232; Humphrey, 1970, 16-17.

    12. Brenner et al., 1976, 561.

    13. Poissonnet et al., 1983, 7; Poissonnet et al., 1984, 3.

    14. Glover and Fisk, 1999, 882; Hepper and Shahidullah, 1994, F81; Sorokin and Dierker, 1982, 725 & 730; Valman and Pearson, 1980, 233-234; Lecanuet and Schaal, 1996, 5-6; Querleu et al., 1989, 410.

    15. Cunningham FG et al., 2001, 133.