Miscarriage is the loss of baby during the earlier weeks of pregnancy and is something that affects many women, their partners (if there is one), older siblings, family and friends. Losing a baby through miscarriage is a heartbreaking experience, no matter how early in the pregnancy it happens, usually rousing deep feelings and emotional reactions.
In Australia, miscarriage is defined as a baby who dies before 20 weeks gestation and/or less than 400 grams in birth weight. Babies who die after 20 weeks gestation (or who weigh more than 400 grams) are classified as being stillborn. This definition is not applied worldwide. The World Health Organisation (WHO) defines miscarriage as being up to 23 weeks of the pregnancy and 500 grams in weight, and other countries will define miscarriage as up until 24, 26 or 28 weeks of pregnany. The definition of a miscarriage is also usually divided up into 'early miscarriages' (before 13 weeks) or 'late miscarriages' (after 13 weeks and before 20 weeks). About 80% of miscarriages will occur before 12 weeks.
The risk of miscarriage is highest immediately after implantation. It is thought that around 50% of all fertilised eggs do not survive, coming away with a normal (or slightly late) period. This is often referred to as an 'unnoticed miscarriage' because it is usually not formally acknowledged by the woman, who is never aware of her pregnancy.
It is estimated that about 15 to 20% of known pregnancies will end in miscarriage. This statistic is often received with surprise and shock, equally because of its high prevalence as well as how little it is acknowledged and talked about openly. While a miscarriage can happen at any time during the first 20 weeks of pregnancy, they more commonly occur around the times the woman's subsequent periods would have been due. That is around 4, 8 and 12 and 16 weeks of the pregnancy.