spontaneous abortion

Last reviewed 01/2018

Miscarriage (previously known as spontaneous abortion) describes the spontaneous discharge of the gestational sac before the fetus is viable. Previously this applied to foetal loss up to 28 weeks gestation but since October 1992, it applies to losses up to 24 weeks. Spontaneous abortion is the process described by the lay public as miscarriage.

Miscarriages occur in up to 10-20% of clinical pregnancies (1). Majority is seen before the thirteenth week (2).

Most of the pregnancies end up as miscarriages even before a woman recognizes that she is pregnant since signs of miscarriage such as bleeding (usually with some abdominal pain and cramping) is mistakenly regarded as heavy or late menses (3).

  • serial measurements of serum beta human chorionic gonadotropin in women who were unaware that they were pregnant have shown that the actual miscarriage rate is around 31% (3).
  • vast majority occur in the first 14 days following conception.
  • after the first few days of conception, the rate of miscarriage reduces sharply until the twelfth week of gestation (4)

Increasing maternal age is associated with increased foetal loss.