Chapter 7 Abortion
INTRODUCTION
Description: Abortion is the loss or failure of early pregnancy in several forms: complete, incomplete, inevitable, missed, septic, and threatened. A complete abortion is the termination of a pregnancy before the age of viability, typically defined as occurring at less than 20 weeks from the first day of the last normal menstrual period or involving a fetus of weight less than 500 g. Most complete abortions generally occur before 6 weeks or after 14 weeks of gestation. An incomplete abortion is the spontaneous passage of some, but not all, of the products of conception, associated with uniform pregnancy loss. A pregnancy in which rupture of the membranes and/or cervical dilation takes place during the first half of pregnancy is labeled an inevitable abortion. Uterine contractions typically follow, ending in spontaneous loss of the pregnancy for most patients. A missed abortion is the retention of a failed intrauterine pregnancy for an extended period; however, with ultrasound studies, this can often be detected significantly sooner than it could be on clinical grounds alone. A septic abortion is a variant of an incomplete abortion in which infection of the uterus and its contents has occurred. A threatened abortion is a pregnancy that is at risk for some reason. Most often, this applies to any pregnancy in which vaginal bleeding or uterine cramping takes place but no cervical changes have occurred.
Prevalence: Estimates for the frequency of complete abortions are as high as 50% to 60% of all conceptions and between 10% and 15% of known pregnancies. Of pregnant women hospitalized for bleeding, 60% have an incomplete abortion. Less than 2% of fetal losses are missed abortions. Septic abortions occur in 0.4 to 0.6 of 100,000 spontaneous pregnancy losses. Threatened abortions occur in 30% to 40% of pregnant women.
ETIOLOGY AND PATHOGENESIS
Causes: Endocrine abnormalities (25% to 50%)—hyperandrogenism, in utero diethylstilbestrol (DES) exposure, luteal phase defect, thyroid disease. Genetic factors (10% to 70%)—balanced translocation/carrier state, nondisjunction, trisomy (40% to 50%, trisomy 16 most common, any possible except trisomy 1), monosomy X (15% to 25%), triploidy (15%), tetraploidy (5%). Reproductive tract abnormalities (6% to 12%)—abnormality of placentation, bicornuate or unicornuate uterus, incompetent cervix, intrauterine adhesions (Asherman’s syndrome), in utero diethylstilbestrol exposure, leiomyomata uteri (submucous), septate uterus. Infection—Mycoplasma hominis, syphilis, toxoplasmosis, Ureaplasma ureolyticus, possibly chlamydia and herpes. Systemic disease—chronic cardiovascular disease, chronic renal disease, diabetes mellitus, systemic lupus erythematosus/lupus anticoagulant. Environmental factors—alcohol, anesthetic gases, drug use, radiation, smoking, toxins. Other factors—advanced maternal age, delayed fertilization (old egg), trauma.
