(Note: This information is intended for general education purposes only, and should not be relied upon as a substitute for professional medical advice.)

From the moment of conception, the human embryo embarks on an amazing journey like no other. The instant the egg and sperm unite, the newly formed conceptus is a unique person in which hair and eye color, gender and all other physical characteristics are determined. During the first 8 weeks after conception, (or 10 weeks post-LMP), the period of ‘organogenesis’ occurs. The baby is termed an ‘embryo’ during this time when all the organs are forming. The following information includes some highlights of the earliest days and weeks of human development.

• The face emerges: discernable eyes, nose and ears.
• Leg and arm buds form.
• The heart forms and begins beating 25 days after conception.
• The baby weighs just under one ounce and is one-half an inch long.
• During a sonogram, the baby's heartbeat can be seen as early as 3 1/2 weeks after conception (or 5 1/2 weeks post-LMP).

• The baby is now termed a 'fetus', which means 'small one' in Latin.
• The baby's hands and feet are fully formed.
• Bones and muscles have developed and the eyelids have formed.
• The heart is almost completely developed and blood is circulating.
• The baby is one inch long.
• Movement can be seen on an ultrasound exam. The mother will not feel the movement for another 2-3 months, however.

9 weeks (post-LMP); 7 weeks (after conception)	9 weeks (post-LMP); 7 weeks (after conception)	10 weeks (post-LMP); 8 weeks (after conception)

13 WEEKS (end of 1st trimester) (3 months) Fingerprints and fingernails have formed. The baby is about 4 inches long.
	13 weeks post-LMP; 11 weeks (after conception)

• The baby can hear and react to sounds.
• The gender can now be determined.
• Lots of activity: swallowing, kicking, sucking thumb
• The baby sleeps off and on.
• "Quickening", or the 1st time the mother feels movement, typically occurs between 17 and 20 weeks.

22 WEEKS (5 months) The baby's eyelashes can be seen. A baby born after 24 1/2 weeks can survive with the support of the neonatal intensive care unit.
	22 weeks post-LMP; 20 weeks (after conception)

• Stenchever: Comprehensive Gynecology, 4th ed., 2001 Mosby, Inc. p. 413
• Life Begins, CD-ROM; 1998; Used with permission from Gordon Harkness; www.lifebegins.com
• Obstetrics: Normal and Problem Pregnancies; 4th ed., 2002 Churchill Livingstone, Inc.; Edited by S. Gabbe, M.D., et al.; p. 734
• "Before You Decide"; 2002 Care Net; (703)478-5661