CIE IGCSE Biology

Revision Notes

16.2.4 Contraception & Fertility

Types of Birth Control

Types of birth control, IGCSE & GCSE Biology revision notesTypes of birth control

  • Birth control methods are important in keeping family sizes small and in limiting the increase in human population
  • Humans can use mechanical, chemical, surgical and natural contraceptive methods to prevent a pregnancy
  • Some birth control methods also give protection from sexually transmitted infections

 

Natural

  • Abstinence
    • avoiding sexual intercourse completely
  • Rhythm method
    • avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs
    • the exact time ovulation happens can be worked out by monitoring body temperature and quality of cervical mucus
    • this is the least reliable method of birth control

Chemical

  • IUD / IUS
    • an intrauterine device or intrauterine system is a small device fitted inside the uterus by a doctor or nurse
    • it releases sex hormones which thicken the mucus produced in the cervix, making it difficult for sperm to swim into the uterus
    • it also thins the lining of the uterus, making it more difficult for a fertilised egg to implant
    • an IUD also interferes with passage of sperm through the uterus, in which way it is acting as a barrier method of birth control
  • Contraceptive pill, implant, injection
    • may contain just progesterone or a mixture of progesterone and oestrogen
    • very effective when taken regularly
    • the hormones can also be delivered from a small skin implant or an injection, both of which last several months and increase the effectiveness as they remove the risk of forgetting to take a pill regularly

Barrier

  • These all work by preventing sperm from reaching the egg
  • Condom
    • latex sheath worn over the penis
    • prevents sperm entering the vagina as ejaculate remains in condom
    • also protects against STIs
  • Femidom
    • latex sheath inserted into the vagina
    • prevents entry of sperm into the vagina
  • Diaphragm
    • a rubber cap that fits over the entrance to the cervix
    • prevents entry of sperm into uterus
    • often used with a spermicide (cream which kills sperm)

Surgical

  • Vasectomy
    • the sperm ducts are cut, meaning that no sperm is present in the semen when ejaculation occurs
    • very effective but difficult to reverse
  • Female sterilisation (tubal ligation)
    • the oviducts are cut or tied off, preventing eggs from reaching the uterus or sperm from reaching the eggs
    • very effective but difficult to reverse
Extended Only

How do Contraceptive Hormones in the Pill Work?

  • They work by mimicking some of the hormone levels during pregnancy
  • By raising the levels of progesterone and oestrogen, the uterus lining is maintained and development of another egg cell is prevented
  • This means that sex at any time of the month cannot cause pregnancy as no egg is released to be fertilised
Extended Only

Fertility Treatments

  • In situations where couples find it difficult to conceive, fertility treatments can improve their chances
  • There are several different options, depending on what the fertility issue is

 

Artificial Insemination (AI)

  • If the male is not producing healthy sperm, donor sperm can be used
  • The sperm are placed into the female’s vagina at the fertile point in her menstrual cycle
  • Social issues to consider include:
    • The male must be able to cope with the fact that the child is not biologically his
    • Sperm donors may father multiple children who are not able to know their parentage

Fertility Drugs

  • This method is used when the female is not producing enough eggs
  • Hormones, including FSH, are given to her to stimulate egg production
  • Social issues to consider include:
    • Several eggs can be released at once so this increases the chance of multiple births (twins or triplets etc)

In Vitro Fertilisation (IVF)

  • If the female cannot conceive naturally even after taking fertility drugs, or if there are issues with both male and female fertility in a couple, IVF can be used
  • This involves fertility drugs being given to the female to stimulate egg production before they are harvested from the ovary
  • The eggs are then inseminated in a petri dish using sperm from the male (‘in vitro’ means ‘in glass’) and, once embryos have formed, they are placed back into the uterus of the female
  • Several embryos are implanted to increase the chance of one developing further
  • Social issues to consider include:
    • IVF is relatively expensive and not all couples can afford it
    • As several embryos are implanted, the risk of multiple births is quite high
    • Some women use IVF to get pregnant at a later age than they would be able to conceive naturally

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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