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Ten Things You Need to Know Before You Take the Contraceptive Pill

27/03/2014 17:20 GMT | Updated 27/05/2014 10:59 BST

1. If taken correctly, the contraceptive pill is 99% effective at preventing pregnancy. It also protects against ovarian and endometrial cancer, anemia and acne.

2. However, unpleasant side effects are common. The pill can cause irregular bleeding, nausea, breast tenderness, weight gain, headache, mood swings, blood clots, varicose veins, thrombosis, and in a somewhat ironic twist, some women find that it also kills the desire to have sex.

3. Oral contraceptives work by increasing levels of something called sex hormone binding globulin (SHBG), which inhibits androgen production and binds to 'free' testosterone. Androgens (like testosterone) modulate sexual function and decreased libido is one of the hallmarks of androgen insufficiency (Bachmann et al., 2002).

4. Research by Sabatini and Cagiano (2006), Panzer (2006) and Wallwiener et al (2010) has found that women using the pill have higher rates of female sexual dysfunction, fewer sexual fantasies, less sex and a reduction in the frequency of orgasm.

5. However, other studies by Fortenberry and Hensel (201.1) Davis et al. ( 2005), and McCall and Meston (2006) have found no evidence of sexual difficulties in women on the pill.

6. And research by McCoy and Matyas (1996) and Caruso et al. (2011) found that women taking oral contraceptives actually experience an increase in libido, increased sexual enjoyment, orgasm frequency, and satisfaction with sexual activity.

7. Even so, Dr. John Bancroft, former director of the Kinsey Institute, suggests that about one in four users of oral contraceptives have sexual side effects. He was involved in a 2001 Kinsey Institute study which found a statistically significant decrease in frequency of intercourse and psychosexual arousability in women on the pill. Also, 8% of the participants dropped out of the study because of sexual side effects.

8. The most frequently prescribed contraceptive pill in the UK is Microgynon 30, not because it has the least side effects, but because it costs the NHS about 90p for a month's supply, compared to £8.39 for a month's prescription of Qlaira, or £3.90 for a months supply of Yasmin.

9. Implants are also problematic: 2.5% of women cite loss of libido as the reason for having an Implanon implant removed (Gezginc 2007).

10. In contrast, several studies have shown that women using the Mirena coil experience greater sexual desire, greater arousal, and less sexual dysfunction (Skrzypulec &Drosdzol 2008, Halmesmäki et al 2007, Oddens 1999).