In Couples with Normal Fertility Potential,
the Fates of 100 Mature Oocytes Released Singly
from the Ovaries at Midcycle Are Approximated
Stage of
development		Surviving
oocytes
and oocyte
progeny		Event or
diagnostic
criteria
Oocytes100Fertilization
Zygotes85 
Preclinical
  pregnancies		60Implantation:
Positive
biochemical
assay (ßHCG)
Clinical
  pregnancies		24Delayed or
missed
menses

Ultrasound
discerns
6 weeks from
last menses,
4 weeks after
ovulation
Mature gestation20Infant delivered
at ±40 weeks
of gestation
sample hypothesis activityExcerpted from: Tagatz, George. 1990. Medical Techniques for Assisted Reproduction. p 91 In: Beyond Baby M. Ethical Issues in New Reproductive Techniques. Edited by Dianne M. Bartels, Reinhard Priester, Dorothy E. Vawter, and Arthur L Caplan.
Click sample quiz question above for a sample sample quiz question.