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Module 9: Oral hormonal contraception

Now we will look at the various contraceptive pills that are available in New Zealand. If we are to be able to counsel men and women regarding contraceptive choices, we need to understand how they work and what the likely side effects are. We will also need to be aware of the contraindications to assist safe prescribing.

There are two main types of oral pills-the combined pill and the progestogen only pill.

The combined oral contraceptive (COC) pill contains two hormones: estrogen and progestogen. COCs work mainly by preventing ovulation. The hormonal doses today are much lower than those when the pill first came onto the market 40 years ago. In NZ we will usually start with prescribing pills which are low dose pills (ie estrogen dose of 35 micrograms of ethinyl estradiol or less) and which contain a second generation progestogen (levonorgestrel or norethisterone). Also we will often tend to start with those pills which are subsidized and only cost $5 for six months supply. Women considering COC use need to have a full medical and family history taken, along with measurement of BP and BMI. This will allow identification of those women with risk factors.

The progestogen only pill (POP) has no estrogen. There are low dose (Noriday and Microlut) and high dose (Cerazette) POPs. The high dose POP, like the COC, works by stopping ovulation. However, the low dose POPs work differently, with the main mode of action being the thickening effect of the progestogen on the cervical mucus thus decreasing sperm penetration. Noriday is subsidized so costs $5 for 6 months. Cerazette costs about  $20-30 for 1 month packet. The POPs can be used by many women who have contraindications to COC pill use.

We aim to have all of you rostered to a family planning clinic visit. There you will sit in with one of the senior nurses during consultations (with the woman's permission). Also there will be one to one time to look at condom use and to go over a pill teach for each of the following combined pill,progestogen only pill -low dose and Cerazette.The rules are different for each of these 3 types of pill.

During this section we will be following the progress of "Diane" as she visits for contraceptive advice. As with all women you will see that the "best" contraceptive for Diane is likely to change, depending on her age and circumstances.


By the end of your study of this section you will be able to:

  • list the different forms of oral hormonal contraception available in New Zealand
  • define the failure rate for both the COC and POP in terms of Pearl Index, and contrast the user failure rate with the theoretical failure rate.
  • list the indications, contraindications, and side effects for the COC and POP
  • describe any specific investigations needed before starting these pills
  • list the principles involved in teaching a woman how to take the COC and POP


Family Planning. Resources. Available from:
Lecturer's notes: You will find that these resources for women are also good for your learning.

Roberts H. How to treat: Contraception. N Z Doctor. 2009 Jul 1:35-41
Fulltext p. 35 , 36 , 37 , 38,41

Royal College of Obstetricians and Gynaecologists, Faculty of Family Planning and Reproductive Health Care, Clinical Effectiveness Unit. Combined hormonal contraception. 2012. Available from:

Royal College of Obstetricians and Gynaecologists, Faculty of Sexual and Reproductive Healthcare, Clinical Effectiveness Unit. Progestogen-only pills. 2016. Available from:

Royal College of Obstetricians and Gynaecologists, Faculty of Sexual and Reproductive Healthcare. UK medical eligibility criteria for contraceptive use. 2016. Available from:

This section is designed to be worked through sequentially. As you work your way through the case you will be pointed to readings, discussion and other activities.

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