Recurrent abortion (pregnancy loss) is defined as three or more consecutive pregnancy losses before 20 weeks’ gestation, each with a fetus weighing less than 500g.
Genetic Error
There is a 50-60 percent incidence of abnormal karyotype in first-trimester spontaneous abortions. Possible causes of genetic errors include balanced rearrangements of parental chromosomes such as translocations, found in approximately 2-5 percent of patients with repetitive abortions.
Uterine Abnormalities
• Defects include congenital uterine anomalies — unicornuate and bicornuate uterus uterine septum.
• Cervical incompetence.
• Submucous leiomyoma.
• Abnormalities due to diethylstilbestrol exposure in utero.
•Asherman’s syndrome
• Generally, losses from anatomic abnormalities occur in the second trimester. Interference with implantation, lack of an adequate blood supply, or growth restriction is possible mechanisms for recurrent loss.
• Polyps, intrauterine adhesions.
Hormonal Causes
• Hypothyroidism and hyperthyroidism.
• Progesterone insufficiency.
• Uncontrolled diabetes mellitus.
• Polycystic ovary disease.
•Reduced ovarian reserve
Infection
Systemic Disease: Systemic causes of recurrent abortion include collagen vascular disease.
Immunologic Factors:-
• Antiphospholipid antibodies (lupus anticoagulant and anticardiolipin antibodies.).
• Thyroid antibodies.
• Increased uterine (NK cells).
• Male-specific minor histocompatibility
Severe maternal illness
• Wilson’s disease.
• Maternal phenylketonuria.
• Cyanotic heart disease.
• Hematologic disorders (hemoglobinopathies or aplastic anemia)
• Inflammatory bowel disease, neoplasia
• Thrombophilia: An important example is the possible increased risk of abortion in women with thrombophilia (propensity for blood clots). The most common problem is the factor V Leiden and prothrombin G20210A mutation. Some preliminary studies suggest that anticoagulant medication may improve the chances of carrying pregnancy to term but these studies need to be confirmed before they are adopted in clinical practice. Note that many women with thrombophilia go through one or more pregnancies with no difficulties, while others may have pregnancy complications. Thrombophilia may explain up to 15 percent of recurrent miscarriages.
Psychological factors
Lifestyle factors: Of specific concern are chronic exposures to toxins, including smoking, alcohol and drugs.
