fertility

• FSH


  stimulates the ovaries to produce oestrogen
• oestrogen


  stimulated the release of LH and inhibits the release of FSH
• LH


  stimulates the release of an egg
• progesterone


  inhibits the release of LH
• hormones can be used to reduce...

  fertility
• how can oestrogen be used in contraception?

  if taken everyday to keep the level of it permanently high, it inhibits the production of FSH and after a while egg development and production stop and stay stopped
• how can progesterone be used in contraception?

  by stimulating the production of thick mucus which prevents any sperm getting through and reaching an egg
• oestrogen and progesterone pill

  - prevents ovulation and thickens mucus from cervix, stopping sperm from reaching an ovum. also prevents implantation of fertilised egg in uterus lining

  - over 99% effective

  - does not protect against sexually transmitted diseases

  - side effects such as headaches and nausea
• progesterone pill


  - thickens the cervical uterus, making it harder for the sperm to penetrate and thins the uterus and kills the embryo

  - over 99% effective

  - fewer side effects than oestrogen and progesterone pill

  - does not protect against sexually transmitted diseases
• contraceptive patch


  a stick-on patch that delivers a precise dose of oestrogen and progesterone into a woman's body through the skin, preventing ovulation and lasts for one week
• contraceptive implant


  insertion of a contraceptive capsule under the skin that provides a continuous amount of progesterone over an extended time and lasts for up to 3 years
• contraceptive injection


  injection of a progesterone into the body and each dose lasts for 2 to 3 months
• IUD (intrauterine device)


  t-shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg. plastic IUDs release progesterone and copper IUDs prevent sperm from surviving in the uterus
• non-hormonal forms of contraception are designed to...

  stop the sperm from getting to the egg
• condoms


  barrier device prevents the exchange of body fluids. male condoms are worn over the penis and female condoms are worn inside the vagina
• what's the only form of contraception that protects against sexually transmitted diseases?

  condoms
• diaphragm


  a shallow plastic cup that fits over the cervix to form a barrier
• spermicide


  agent that kills sperm and is usually used with other forms of contraception
• sterilisation


  involves cutting or tying the fallopian tubes in a female or the sperm duct in a male. this is a permanent procedure however there is a very small chance that the tubes can rejoin
• natural methods


  pregnancy may be avoided by finding out when in the menstrual cycle the woman is most fertile and avoiding sexual intercourse on those days. not very effective
• abstinence


  act of refraining from sexual intercourse and the boy way to be sure that the sperm and egg do not meet
• hormones can be used to...

  increase fertility
• why may some women be infertile?

  low levels of FSH results in eggs not maturing, meaning no eggs are released and women can't get pregnant
• what hormones are given as a fertility drug to stimulate ovulation?

  FSH and LH
• pros of hormone induced fertility

  helps a lot of women get pregnant when they previously couldn't
• cons of hormone induced fertility

  - may not work

  - expensive

  - too many eggs could be stimulated, resulting in unexpected pregnancies (twins, triplets, etc.)
• IVF (in vitro fertilisation)

  involves collection eggs from a woman's ovaries and fertilising them with sperm outside of the body
• ICSI (intro-cytoplasmic sperm injection)

  where the sperm is injected directly into an egg - useful if the man has a very low sperm count
• eggs that are fertilised outside of the body are grown into embryos in...

  a laboratory incubator
• what happens once an embryo has formed outside of the body?

  one or two of them are transferred to the woman's uterus to improve the chance of pregnancy
• what hormones are given to the woman before egg collection?

  FSH and LH to stimulate several eggs to mature so that more than one egg can be collected for increased success rate
• pros of IVF


  fertility treatment can give an infertile couple a child
• cons of IVF


  - multiple births can happen if more than one embryo grows into a baby: risky for both mother and babies (higher risk of miscarriage, stillbirth etc)

  - success rate is low (only 26% in the UK) makes the process emotionally stressful and upsetting

  - physically stressful for the woman: some have a strong reaction to the hormones (e.g. abdominal pain, vomiting, dehydration)

  - expense: each round of IVF and keeping the embryos incubated costs money
• how have advances in technology improved IVF?

  - advances in microscope techniques have helped to improve the success rate

  - specialised micro tools have been developed to use on the eggs and sperm under the microscope: they're also used to remove single cells from the embryo for genetic testing (to check if they're healthy)

  - development of time-lapse imaging means that the growth of embryos can be constantly monitored improving success rate
• why are some people against IVF?

  - it often results in unused embryos that are eventually destroyed (unethical because each embryo is a potential human being)

  - genetic testing of embryos before implantation raises ethical issues (could lead to the selection of preferred characteristics e.g. gender, eye colour etc