Recurrent miscarriage is three or more consecutive pregnancy losses. In contrast, infertility is the inability to conceive. In many cases the cause of RPL is unknown. After three or more losses, a thorough evaluation is recommended by American Society of Reproductive Medicine. About 1% of couples trying to have children are affected by recurrent miscarriage. Causes
There are various causes for recurrent miscarriage, and some can be treated. Some couples never have a cause identified, often after extensive investigations. About 50–75% of cases of recurrent miscarriage are unexplained. Chromosomal disorders
A balanced translocation or Robertsonian translocation in one of the partners leads to unviable fetuses that are miscarried. This explains why a karyogram is often performed in both partners if a woman has experienced repeated miscarriages.Aneuploidy may be a cause of a random spontaneous as well as recurrent pregnancy loss. Aneuploidy is more common with advanced reproductive age reflecting decreased germ cell quality.Larger chromosomal disorders are generally detected on karyotype. In couples where a miscarried embryo has an abnormal karyotype, 76% of subsequent miscarried embryos have shown abnormal karyotypes as well. On the other hand, this group of couples have a better long-term live birth rate than those where miscarried embryos have normal karyotype. Lifestyle factors
While lifestyle factors have been associated with increased risk for miscarriage in general, and are usually not listed as specific causes for RPL, every effort should be made to address these issues  in patients with RPL. Of specific concern are chronic exposures to toxins including smoking, alcohol, and drugs.
Acetohydroxamic acid (also known as AHA or by the trade name Lithostat) is a drug that is a potent and irreversible enzyme inhibitor of the urease enzyme in various bacteria and plants; it is usually used for urinary tract infections. The molecule is similar to urea but is not hydrolyzable by urease; it thus disrupts the bacterias metabolism through competitive inhibition. Orphan drug
In 1983 the US Food and Drug Administration approved acetohydroxamic acid (AHA) as an orphan drug for "prevention of so-called struvite stones" under the newly enacted Orphan Drug Act of 1983. AHA cannot be patented because it is a standard chemical compound. See also
Salicylhydroxamic acid


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