1. Biology of Fertility Control

2. Learning Outcomes Infertility treatments and contraception are based on the biology of fertility. Cyclical fertility in females leading to a fertile period. Continuous fertility in males. Calculation of fertile periods and their uses.

3. Continuous versus Cyclical Fertility In human males, there is a relatively constant level of FSH and ICSH in the bloodstream Therefore, a steady quantity of testosterone is secreted and a steady quantity of sperm produced As a result, human males are continuously fertile

4. Cyclical Cyclical fertility is in marked contrast with the continuous fertility in males The interplay of pituitary and ovarian hormones results in the period of fertility being restricted to the 1-2 days following ovulation

5. Calculation of Fertile Period The indicators ‘Temperature’ and ‘Mucus’ can be used by a woman to calculate her fertile period This is obviously of use to a couple who are wishing to conceive

6. Temperature Approximately 1 day after the LH surge which triggers ovulation, a woman’s body temperature rises by 0.2-0.5C It remains at this elevated level for remainder of the luteal phase Fertile period lasts for about 1-2 days The infertile period is resumed after the 3 rd daily recording of higher temperature

8. Mucus The cervical mucus secreted into the vagina during the fertile period is thin and watery This allows easy access of sperm to the female reproductive system After ovulation, progesterone causes the mucus to gradually increase in viscosity

9. Try these questions.... 1.Distinguish between the terms ‘continuous fertility’ and ‘cyclical fertility’ 2.For how long does a woman’s fertility period last? 3.Describe two signs that give an indication of when this time occurs

10. Answers.... 1.Men are continuously fertile, sperm are produced at all times throughout any given month. Woman are cyclically fertile. One or more eggs are released and available to be fertilised for a short period of time in any given month. 2.1-2 days 3.Thinner consistency of cervical mucus and increase in body temperature

11. Glossary CONTINUOUS FERTILITY – men are said to be continuously fertile as the feedback effect of testosterone maintains relatively constant levels of FSH and ICSH meaning a steady quantity of sperm are always produced CYCLICAL FERTILITY – women’s fertility period is restricted to 1-2 days per month due to the delicate interplay of pituatry and ovarian hormones that occur in the female body FERTILE PERIOD - the time in the menstrual cycle when fertilisation is most likely to be possible, 1-2 days immediately following ovulation