1. Menstruation, Fertilization & Pregnancy
Ms. Markowski

2. Menstruation
4 phases: follicular phase, ovulation, luteal phase, menstruation
Follicular phase (~10 days):
follicles in ovaries are told by hormones to develop an egg to be released
Lining of uterus begins to build to prepare for implanation of fertilized egg
Ovulation (~3-4 days):
Egg is released from ovary into one of the fallopian tubes

3. Menstruation 3. Luteal Phase: ~10-14 days after last menstrual cycle
1st 2 days of luteal phase is greatest chance of fertilization!
Lining of uterus continues to build while egg travels from fallopian tube to uterus
If egg is fertilized, it will divide and implant itself in the lining of the uterus and pregnancy begins
If egg is NOT fertilized, menstruation begins

4. Menstruation 4. Menstruation: ~3-7 days
If an egg is not fertilized, hormone levels drop, signaling lining of uterus to detach
Uterine lining, unfertilized egg and blood will flow through the vagina
Commonly known as a “period”
After “period” is over, a new cycle begins again!
NOTE: many things can change how regular or irregular a woman’s cycle is, such as:
Stress, under-eating, over-eating, jet lag, illness, birth control pills, drugs, exercise level, etc.

5. Picture of Menstrual Cycle

6. STOP and THINK!
Do you notice how much variation exists between different women’s cycles and even within one woman’s own cycle?
Do you better understand why it can be so complicated to predict when a woman is ovulating or not?

7. Fertilization and Development
The process of a sperm joining with an egg to create a zygote
Complete details of pregnancy and development are beyond the scope of this course, but the following is a brief overview of events.

8. Fertilization and Implantation
Sperm and egg usually join together in the fallopian tube
Fertilized egg begins to undergo millions of cell divisions (called mitosis)
Travels to and implants itself in lining of uterine wall

9. Fertilization and Implantation
Uterine wall
Blastocyst
Morula
4 cells
2 cells
Zygote
Ovary
Fallopian tube
Day 3
Day 2
Day 1
Day 4
Fertilization
Day 0
Day 7
Implantation of blastocyst
Egg released by ovary

10. Development Three main phases:
Implantation: into lining of uterus
Gastrulation: germ layer development for future development of internal organs and tissues
Neurulation: development of the nervous system
After about 40 weeks, the fertilized egg has grown from a zygote, to a morula, to a blastocyst, to an embryo, to a fetus,
to infant

11. STOP and THINK! What does it mean for you?
Want to avoid an unwanted pregnancy?
Be educated!
Ask questions….check out some common questions on the next slide…

12. STOP and THINK!
But what if we have sex while she is having her period?
It is still possible for a woman to get pregnant even if she is menstruating.
The younger the woman, the more likely her cycle is going to be irregular as her body adjusts to changes in hormone levels.

13. STOP and THINK!
Can a woman get pregnant by having oral sex because sperm (ejaculate) enter her digestive system?
No, if sperm (ejaculate) have ONLY entered the mouth, there is no connection between the digestive system and the reproductive system.
However, if ejaculate is deposited near the vagina, it is possible for a sperm to swim up to an available egg.
BE CAREFUL!

14. STOP and THINK!
But what if I ejaculate outside her body or “pull out”?
Smaller amounts of sperm are released in “pre-ejaculate fluid” during intercourse
Therefore, it is very possible to get someone pregnant even if you “pull out” before ejaculation
A sperm only needs to swim up the vagina into the uterus or fallopian tube to meet the egg. Sperm on the labia majora and minora can be capable of doing this
Bottom line: there is NO guarantee to avoid pregnancy 100% except by abstinence

15. Resources:
Miller, K. & Levine, J. (2005). Prentice Hall: Biology [CD ROM]. Pearson Education, Inc.
Bold, M., Jennings, G., & Brock, L. (2005). FS 5023 Family Sexuality [CD ROM]. Department of Family Sciences, Texas Woman’s University.