Miscarriages

Recurrent, habitual abortion is not easy to diagnose because it has no precise definition. It is referred to as two successive abortions, or three or more, and sometimes includes women with a live birth followed by successive abortions. Two thirds of women succeed in establishing pregnancy after three successive abortions, although birthweights among the offspring are lower. The condition might be restricted to fewer than 1% of women, or to less than 1% among pregnant women.

There is a remarkable lack of clarity in interpreting the causes of habitual abortion after natural conception. An immense number of causes have been offered, which is in itself a testimony to an almost total absence of insight into the primary factors. There are numerous reported causes and others are still being added, including variations in activated factor XII.

Estimates of the frequency of recurrent abortion also depend on the methods used for diagnosis. Clinical assessments seem to be insensitive. Sonography is of intermediate value only, and biochemical assessments of biological fluids are the most sensitive in introducing some concepts to explain the underlying problems. The condition might be increasing through the spread of IVF and other forms of assisted conception in infertile women. Rates may also be increasing through a greater delay in the age of childbearing and greater levels of stress in today's society.

Women who abort after IVF or natural conception tend to have another abortion in a succeeding cycle. Approximately 48% of women aborting in one pregnancy after nonassisted conception have a miscarriage during a later pregnancy. In contrast, only 6.7% of women abort if they have already carried a pregnancy to term. Successive abortions occur at different gestational ages in the same patient and might be associated with several factors, even within one couple. They may also be familial. (Source: Principles and Practice of Assisted Human Reproduction. Edwards and Brody. W.B Saunders Company, 1995)