Miscarriage, Prematury Birth. Isthmico-Cervical Incompetence

Miscarriage. Premature birth. Synonyms: pregnancy loss, misbirth, preterm labor (PTL), preterm birth

Miscarriage. Definitions. Abortion (miscarriage) is a termination of pregnancy before the fetus is viable. It is termination of pregnancy prior 22nd completed week of pregnancy. The World Health Organization (WHO) defines it as expulsion or extraction of an embryo or fetus weighing 500 g or less. The term "embryo" is used at term of pregnancy < 10 weeks; the term "fetus" is used after the 10th week gestation.

The term abortion is more commonly used as a synonym for induced abortion, the deliberate interruption of pregnancy, as opposed to miscarriage, which connotes a spontaneous or unintentional (natural) loss of pregnancy.

Early miscarriage/abortion (prior 14 weeks gestation) and late miscarriage/abortion (from 14th week up to 21 wks+6 days of pregnancy) are distinguished.

The miscarriage of 3 or more consecutive pregnancies with no intervening childbirth is termed habitual miscarriage or recurrent miscarriage.

Usually an infant born at a gestational age less than 22 weeks is nonviable.

Incidence. Approximately 20 % of all pregnancies terminate in spontaneous abortion and about 80% of them occur within 2 to 3 month of gestation.

Etiology. In more than 50% of cases the cause of prematurity is unknown. Usually there are some reasons; the most common are the following:
- uterine abnormalities (saddle-like uterus, uterus septus, uterus bicornis), cervical insufficiency,
- hypoplastic uterus, hysteromyoma;

- chromosomal anomalies (embrionic anomalies);
- immunologic disorders (e.g. Rh-incompatibility, antiphospholipid syndrome);
- endocrine disorders (diabetes mellitus, obesity, thyroid diseases, systemic lupus
- erythematosus (SLE), hypothyroidism and hyperthyroidism);

- infectious diseases (urinary tract infections, treponema infections, dysentery, rubella, cytomegalovirus [CMV], and mycoplasmal, ureaplasmal, listerial, toxoplasmal infections);
- extragenital diseases (anemia, decompensated heart lesions, chronic hypertension, etc.);

mental disorders;
- complicated pregnancy (preeclampsia, placental abruption, intrauterine infection, premature rupture of the membranes, hydramnios);

- various traumas (contusions, bone fractures);
- harmful habits (smoking, alcohol, cocaine and other illicit drugs);
- occupational diseases (vibration, chemical factor, etc.);
- overwork and malnutrition, multiple pregnancies

Early Spontaneous Abortion. In abortion the conceptus is gradually separated from the uterus. The blood vessels of the decidual membrane are ruptured. The separated ovum dies and becomes impregnated with blood. The uterus develops contractions, the cervical canal dilates and the conceptus is expelled from the uterus. The woman feels pains in the low abdomen, their intensity increasing with the gestational age. Another symptom is bleeding, the intensity depending on the stage of abortion and the gestational age. An excessive bleeding occurs in most cases of early abortion.

The mechanism of late abortion is practically the same as in labor: the cervix dilates, the uterine contractions increase, the fetus is delivered, and placental delivery occurs after the fetal one.

The following stages of abortion are distinguished:
- Threatened abortion
- Inevitable abortion (abortion in progress)
- Incomplete abortion
- Complete abortion

Threatened Abortion. The conceptus remains attached to the endometrium and its connection with the uterus is disrupted only over a small area. Bleeding is absent or insignificant (blood spotting), the cervix is closed, the uterus size corresponds to gestational age (Fig.167). The pregnant feels discomfort or insignificant pain in the lower abdomen.

Fig. 167. Threatened spontaneous abortion