Do women always bleed from the hymen when losing their virginity?

Question

In a lot of cultures, there are customs and rituals upon a woman to losing her virginity, based on bleeding from the hymen, such as using a white bedsheet on the wedding night. If there is blood after intercourse, it 'certifies' that the bride was a virgin.

Do all women always bleed when the hymen is broken in sexual intercourse?

Is it possible for a virgin who has not previously damaged her hymen to not bleed at all?

Let's assume in all these cases that the hymen was not broken previously due to injury, masturbation, etc.

Answer 1

According to The experience and responses of Swedish health professionals to patients requesting virginity restoration (hymen repair) Reproductive Health Matters, volume 18, pages 38-46.

Two studies in English report that 40–80% of women do not bleed upon initial coitus [italics in original text]

The above article references the above sentence to:

Violence against women in Arab and Islamic countries, Archives of Women's Mental Health, 6 (3) (2003), pp. 165–171

and

Should doctors reconstruct the vaginal introitus of adolescent girls to mimic the virginal state? Education about the hymen is needed British Medical Journal, 316 (7129) (1998), p. 461.

The article goes on to state:

Factors that may increase the likelihood of bleeding at that time are forced sexual relations, lack of arousal or lubrication, vaginal infection, genital malformation (e.g. imperforate hymen), generalised bleeding disorder, or if the girl is pre-puberty.

Answer 2

No. they don't. First, they hymen is more like a donut shape than a trampoline. The vaginal canal is still accessible while it's intact. This allows menses to occur in virginal women. Some women have very fragile hymens that can be lost during childhood play. Such girls should not be bleeding during first sex. Some women can grow back their hymen and will bleed each time they have sex for some time. Some hymens are very strong and do not break during sex. In some cultures, they may/must be removed by a doctor.
[1] http://www.yourtango.com/201172815/7-things-you-didnt-know-about-hymen