Contraception

Published on 09/03/2015 by admin

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Chapter 7 Contraception

Caroline De Costa, Michael Flynn

A standard measure of contraceptive effectiveness is the Pearl index—the number of pregnancies per 100 woman-years in those at risk of pregnancy. One woman-year equals 12 menstrual cycles.

Natural methods

Natural methods are based on avoiding sexual activity that might lead to conception at the time when the ovum can be fertilised. It is necessary to predict the time of ovulation (generally by observing changes in body temperature) and to allow for the time that the sperm can survive with fertilising potential in the female genital tract. Intercourse is prohibited until 72 hours after the rise in basal body temperature. The Pearl index is 25/100 woman-years; with coitus interruptus, it is 18/100.

Barrier methods

Diaphragm

The diaphragm lies diagonally across the cervix, vaginal vault and anterior vaginal wall (extends from posterior vaginal fornix to behind pubic bone). Types of design are arcing, coil or flat; it is manufactured from natural rubber, latex or silicone.

Function

• acts as retainer of spermicide
• keeps sperm away from alkaline cervical mucus, as sperm die in the acidic pH of the vagina
• prevents physical aspiration of sperm into the cervix and uterus

Effectiveness

• with perfect use, Pearl index 6/100 (normally increased by 3–7 times)
• may be protective against some sexually transmitted diseases, but not human immunodeficiency virus (HIV)
• not suitable for women with anatomical abnormalities of the genital tract and those with large cystoceles, rectoceles or uterine prolapse

Cervical/vault caps

• three types: cervical, vault, vimule (both cervix and vault); manufactured from latex, silicone
• function: to occlude the cervix
• spermicides recommended with use
• Pearl index 7/100

Advantages

• can be used in the presence of genital prolapse
• no rim; therefore, not felt by partner
• fitting not changed by changes in the size of the vagina

Sponge

• function: release spermicide; absorb the ejaculate; block the cervix
• Pearl index 17/100

Condoms

• reduce transmission of sexually transmitted diseases, including HIV
• non-latex condoms (polyurethane) available
• Pearl index, with perfect use, 2/100

Female condoms

• cover the vulva and may protect against infections such as herpes simplex and human papillomavirus

Spermicides

• most commonly used is nonoxynol-9; newer agents: octoxynol, benzalkonium chloride
• act by disrupting sperm cell membrane, causing rupture of spermatozoa
• available in gels, foams, creams, pessaries and capsules
• variable efficacy depending on doses, formulations and compliance
• may protect against sexually transmitted disease, and have in vitro anti-HIV properties

Intrauterine contraceptive devices

Types

• copper, to increase effectiveness and reduce the surface area (e.g. Multiload 375, Slimline TT380)
• progestogen-containing device (e.g. levonorgestrel-releasing intrauterine device (LNG IUD))

Mechanisms of action

• both types: prevent fertilisation of the ovum
• both types: foreign body response in myometrium interferes with implantation of the blastocyst
• both types: interfere with sperm transport
• LNG IUD only: causes endometrial atrophy, thickening of cervical mucus, prevents or delays ovulation in some women; oligomenorrhoea or amenorrhoea a normal side effect

Effectiveness

• Copper devices have a Pearl index in the first year of 2–3/100, later falling to lower than 1/100.
• They can be used as a postcoital contraceptive.
• Progesterone devices have a failure rate of 0.2%.

Counselling

• Take a past medical, surgical and social history.
• Discuss risks.
• The ideal patient for the intrauterine contraceptive device is a multiparous, monogamous woman with regular, normal periods.

Before insertion

• Explain procedure and risks, and acquire consent.
• Conduct a general physical examination.
• Perform a vaginal/pelvic examination.
• Obtain bacteriological, Chlamydia swabs, and cervical cytology if indicated.

Insertion

• Preferably insert at menses or up to day 10 of the cycle.
• For postcoital contraception, it may be effective up to 5 days postcoitus.
• For postpartum contraception, insert at 6 weeks after delivery.
• Training in insertion procedure is essential.

Change of the contraceptive device

• Multiload 375 devices require a change every 5 years.
• Progesterone (LNG IUD) is effective for 5 years.

Risks

• increased menstrual blood loss and dysmenorrhoea in copper devices
• incidence of uterine perforation (usually at time of insertion) 1 in 1000
• infection: for pelvic inflammatory disease, relative risk in the first 6 months 1.6; Actinomycosis israelii is usually an incidental finding at cervical cytological examination; may be associated with use of an intrauterine contraceptive device (see Ch 11)
• no protection against sexually transmitted infections
• increased risk of abortion, premature labour and delivery if a pregnancy occurs while the device is present
• ectopic pregnancy more frequent than in women not using an intrauterine contraceptive device (as device does not prevent ectopic)
• no reduction in fertility after using an intrauterine contraceptive device

Oral contraceptives

Combined oral contraceptive pill (COCP)

Two formulations

• monophasic: contain same oestrogen/progestogen throughout 21 or 24 days of course
• trisphasic: variations in oestrogen/progestogen content to reduce side effects

Mechanisms of action

• inhibit the oestrogen-mediated positive feedback that is required for the mid-cycle luteinising hormone (LH) surge
• inhibit follicle-stimulating hormone (FSH) release, thus preventing follicular maturation
• produce a change in cervical mucus
• reduce endometrial receptivity to the blastocyst

Assessment before commencing COCP

• Assess for and advise/manage risk factors such as hypertension, cigarette smoking and abnormal bleeding, and risk factors for thrombosis.
• Perform cervical cytology and breast examination.
• Contraindications include the presence of an oestrogen-dependent tumour, unexplained vaginal bleeding, pregnancy, breastfeeding, previous thromboembolism or cerebrovascular accident, known thrombophilia, hepatic dysfunction, severe migraine, >15 cigarettes daily in women >35 years, type 2 diabetes with complications, body mass index (BMI) >40.
• The woman must understand method and solutions to problems (see below).

Side effects and risks

• deep venous thrombosis

• significant increased risk with use of ethinyloestradiol at doses of 100 μg or higher
• hypercoagulation (may occur, but will reverse within 1 week of cessation of the oestrogen)

• cardiovascular disease: no statistically significant increased risk of hypertension in non-smokers
• malignancy: reduced relative risk of endometrial and ovarian cancer, which may continue for some time after cessation of use
• decrease in functional ovarian cysts; useful in managing polycystic ovarian syndrome (PCOS)
• carbohydrate metabolism: ethinyloestradiol doses lower than 40 μg little or no effect
• decreased menstrual loss and dysmenorrhoea
• improvement in acne

Missed pills

The high-risk time to miss pills, in terms of risk of pregnancy, is at the end of a packet or at the start of a new packet. Manage by continuing oral contraception and use other forms of contraception for 7 days. If these 7 days continue beyond the current 21-day packet, then start the next packet without a normal break (i.e. do not take the inactive pills).

Problems and solutions

• androgenic side effects: use desogestrel, gestodene, drospirenone, cyproterone acetate; increase oestrogen content
• anticonvulsant therapy: use monophasic 50 μg ethinyloestradiol
• breakthrough bleeding, amenorrhoea, dry vagina: increase oestrogen content
• breast tenderness: increase progestogen, reduce oestrogen
• antibiotics: little effect on contraceptive efficacy except for rifampicin; when using antibiotics, continue oral contraception and use other methods during and for 7 days after treatment; hormone-free interval should be omitted if <7 active pills remain in packet (i.e. continue directly with active pills in next packet)
• lactation: combined oral contraceptives may interfere

Progestogen-only pills

These pills contain progestogen only (levonorgestrel or norethisterone). All pills are active, and are taken continuously with no breaks. The mechanism of action is thickening of the cervical mucus, preventing sperm transport, rather than inhibiting ovulation (also possible interference with tubal motility and implantation). The pill should be taken at the same time each day, as efficacy is less than COCP. It is useful in breastfeeding women and those with certain medical contraindications to COCP.

Contraceptive implants

Depot medroxyprogesterone acetate (DMPA)

• dose: 150 mg by intramuscular injection every 12 weeks
• start first injection within 3 days of menstrual period
• Pearl index below 1/100 (i.e. as effective as COCP)

Mechanisms of action

• inhibits ovulation
• atrophies endometrium
• increases viscosity of cervical mucus
• reduces motility of fallopian tubes

Side effects

• irregular vaginal bleeding, especially in first 3 months
• amenorrhoea in 50% of women by 12 months
• restoration of ovulation taking up to 18 months

Subcutaneous progestogen implants

Etonogestrel’s mechanisms of action are similar to those of DMPA. It represents a rapidly reversible contraception method. Training in insertion and removal procedures is essential.

Combined vaginal ring

This is a combined hormonal contraceptive ring inserted vaginally by the woman and left in place for 3 weeks and removed for a 7-day interval, as with placebo pills in COCP packs (e.g. NuvaRing). It inhibits ovulation, thickens the cervical mucus preventing sperm migration, and may interfere with implantation. It is a rapidly reversible method of contraception. Efficacy is equivalent to COCP.

Assessment

• as for COCP
• useful for women having difficulty with daily pill taking and women with inflammatory bowel disease
• contraindicated in immediate postpartum period
• the woman must understand method and how to insert ring

Side effects and risks

• may be accidentally expelled (e.g. in presence of prolapse, chronic constipation)
• possible increased vaginal discharge, vaginal infections
• decrease in menstrual loss and dysmenorrhoea
• contraindicated for first 6 months of breastfeeding
• late removal or late reinsertion of ring: cover insertion of new ring with condoms or other methods for 7 days

Pregnancy interception (emergency contraception)

Hormonal methods

• effectiveness dependent on time interval from unprotected intercourse to administration of medication; more effective when taken earlier
• effective preovulation; probably ineffective postovulation
• Yuzpe regimen: oral ethinyloestradiol 100 μg and levonorgestrel 500 μg with an antiemetic; repeat dose in 12 hours; take within 72 hours of coitus; needs follow-up for failure of method, future contraception, risk of ectopic pregnancy and risk of sexually transmitted infections
• progestogen-only: levonorgestrel 750 μg immediately; repeat dose in 12 hours, or 1.5 mg single dose
• antiprogesterone: mifepristone RU-486 (not yet available in Australia)
• intrauterine contraceptive device (copper): effective up to 5–8 days after coitus

Male contraception

Gonadotropin-releasing hormone (GnRH) analogues

• reduce testosterone levels and libido
• GnRH with testosterone may block spermatogenesis

Steroids

• androgens cause a negative feedback that results in a fall in gonadotrophins
• progesterone and testosterone result in oligospermia

Antiandrogen (cyproterone acetate)

• inhibits spermatogenesis
• reduces potency and libido

Gossypol

• interferes with the acrosome

Sterilisation

Female sterilisation

Abdominal/laparoscopic

• Methods include fimbriectomy, diathermy, Pomeroy technique, Falope rings, Hulka or Filchie clips.
• Failure rate of 2–4/1000 may rise if performed at caesarean section or immediately postpartum.

Hysteroscopic

• Block fallopian tubes by inserting titanium microinserts via tubal ostia.

Male sterilisation

• Vasectomy is not associated with changes in the endocrine function.
• Pearl index is 0.2/100.

Further readings

Sexual Health and Family Planning Australia (SH&FPA). Contraception: an Australian clinical practice handbook. Canberra: SH&FP; 2008.

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