Dr Gary Swift
Fertility Awareness & Contraception
We’re talking about fertility awareness and contraception. Women are faced with a diverse range of options for contraception. To appreciate how the various methods work and how they impact we must understand the physiology.
Women are born with their lifetime supply of eggs (oocytes). These are in a constant state of decline no matter what physiological intervention occurs until the menopause at approximately 51.7 years of age (range 40-60). In a typical 28 day menstrual cycle with day 1 being the first day of a period ovulation or egg release tends to occur on or about day 14. The range however is from day 10-18. After intercourse living sperm are still detectable up to 3 days. These facts determine the “fertile window”.
Women’s bodies will mostly give signs when fertility is optimal. Some women may experience discomfort in the ovary with the dominant follicle just prior to or after ovulation. As contraception is the opposite to fertility, these signs and physiologic changes make up the basis for natural contraception (The Billings Method) where couples avoid intercourse when the woman is most fertile. It requires motivation and diligence, but can be very successful.
Methods where the male withdraws prior to ejaculation reduce the chance of pregnancy however effectiveness is limited by the fact that some sperm are released from the penis in the pre-ejaculate fluid. This method may be OK for couples who like to take chances and wouldn’t mind an accidental pregnancy but is not generally reliable.
Condoms provide barrier contraception and hence prevent pregnancy and the transmission of sexually transmitted infections, very important for women (and men) who may not be in a regular relationship or have multiple partners.
Diaphragms are not commonly used these days and need to be fitted by a trained GP or Family Planning Clinic. They are good for women who can’t tolerate or don’t want hormonal based options. They provide some STD protection and may be used with spermicidal gels for greater effectiveness. The main criticism is the limiting of spontaneity as preparation and planning are required for effective use.
The remaining options are hormonal based and operate by estrogen suppressing the hormonal signals from the brain to the ovaries. This effect is used in the combined OCP in various forms and doses. Another hormone, progesterone thickens cervical mucus, suppresses endometrial development and may act centrally to suppress ovulation.
There are many brands and formulations of combined oral contraceptive pills on the Australian market. This reflects the fact that no one pill suits all women. The different pills contain varying types and doses of estrogens and progesterones. Pharmaceutical companies have made significant inroads into packaging and reminder systems to optimise compliance.
The progesterone-only or minipill contains only one hormone and therefore is less effective than the combined pill. The failure rate even if taken correctly is about 3% as ovulation is not reliably suppressed, the main effect being on the cervical mucus and endometrium (uterine lining). This formulation is ideal for breast feeding mothers as it has no effect on breast milk supply. Women who can’t tolerate estrogens due to migraines, allergies or other side effects may find this modality useful.
Other progesterone based contraceptives include the subcutaneous progesterone rod (Implanon®) which is inserted under the skin of the upper arm and release a small amount of progesterone hormone over three years.
Depo-Provera® is an injectable progesterone administered three monthly by a doctor or nurse. It is very effective as a contraceptive agent and 85% of women will stop having periods within 12 months of regular injections.
The levonorgestrel intra-uterine device (Mirena®) is inserted into the uterine cavity in the office under local anaesthetic or under general anaesthesia in an operating theatre. It releases a small dose of progesterone for 5 years and in 70% of women supresses all menstrual bleeding. Removal can be performed at any time and fertility is restored in most within 1-2 months.
Permanent sterilization options include tubal ligation at laparoscopy (day case surgery under GA), Hysteroscopic tubal occlusion (day case GA or sedation) and Vasectomy for men under local or GA. These methods are designed to be permanent. Some cases may be surgically reversed or require IVF for subsequent pregnancy if circumstances change or there is a change of mind.
As with all medical matters an individual approach to contraception with your GP or Gynaecologist is essential to decide on the right option and to effectively adjust or trouble-shoot any problems.