Inevitable Abortion (Abortus insipiens)

Inevitable Miscarriage(Abortus insipiens) is a clinical condition in which pregnancy ends before the twentieth week and retention of the pregnancy product within the uterus is no longer possible.

This condition is characterized by the addition of cervical dilation (cervical dilatation) to the signs of threatened miscarriage, namely bleeding and pain. Pregnancy continuation is no longer possible at this stage and the process progresses toward the natural expulsion of the pregnancy material. This clinical picture, often accompanied by rupture of the amniotic sac (membrane rupture), is recognized as a clinical stage of spontaneous abortion.

^{Normal Pregnancy and Inevitable Miscarriage Symptoms}

^{(Generated by Artificial Intelligence)}

Inevitable miscarriage and other types of miscarriage have evolved diagnostically with the discovery of biochemical substances secreted by the pregnancy product. In the early twentieth century, the concept was proposed that the fertilized ovum secretes specific substances; in 1927–1928, Ascheim and Zondek successfully identified human chorionic gonadotropin (hCG), laying the foundation for pregnancy tests.

In subsequent years, other proteins reflecting placental function were identified. In 1936, Ehrhardt detected lactogenic activity in the placenta, and in 1961, Ito and Higashi isolated hPL.

Another pregnancy-specific protein, SP1, was discovered by Tatarinov and Masyukevich in 1970 and isolated by Bohn in 1971. The discovery of these markers has played a significant role in the biochemical monitoring of processes that begin as threatened miscarriage and may progress to inevitable miscarriage.^【1】

Approximately 10–15% of pregnancies in the general population end in spontaneous miscarriage. Studies based on hospital data show that inevitable miscarriage accounts for a significant proportion of all miscarriage cases. One study reported that 38.5% of miscarriage cases were diagnosed as inevitable miscarriage.^【2】

Data from another center observed that cases diagnosed with threatened miscarriage or inevitable miscarriage accounted for 76.8% of all miscarriage referrals. Maternal age is a prominent risk factor; the rate of early miscarriage is 9–17% among women aged 20–30, but can rise to 75–80% in women aged 45.^【3】

The most common cause of progression to inevitable miscarriage is chromosomal abnormalities. Chromosomal disorders underlie approximately 55% of spontaneous miscarriages. Other contributing factors include hormonal, metabolic, infectious, placental, chemical, and anatomical causes.

Among hormonal causes, progesterone insufficiency (luteal phase defect) is most prominent. Research has reported that advanced maternal age may increase risk, but no definitive profile has been established linking parity or prior miscarriage history directly to the condition.

The fundamental pathophysiological mechanism involves uterine contractions aimed at expelling the pregnancy product and cervical dilation resulting from these contractions or structural changes. In threatened miscarriage, the cervix remains closed; as the process progresses, cervical canal dilation occurs, leading to inevitable miscarriage. Mechanical disruption of intrauterine decidual cells during placental separation or abortion can elevate maternal serum CA-125 levels, indicating degeneration of the decidua and amniotic membranes.^【4】

In patients diagnosed with inevitable miscarriage, vaginal bleeding and pain symptoms are significantly more severe and pronounced than in threatened miscarriage. Pain is typically cramp-like and felt in the lower abdomen or back.

The most distinctive finding on physical examination is an open cervical os. In most cases, rupture of membranes (water breaking) also accompanies the clinical picture. At this stage, part of the pregnancy product may be visible or palpable within the cervical canal.

Diagnosis is established through clinical examination and ultrasonographic evaluation. Pelvic examination confirms the diagnosis when the cervix is open and pregnancy material is observed within the cervical canal. Ultrasonography may reveal disruption of the gestational sac, its displacement toward the cervical canal, or absence of fetal cardiac activity.

Biochemically, failure of expected increases or a decline in serial measurements of placental proteins such as hCG, hPL, and SP1 is a strong indicator of pregnancy loss. Particularly, SP1 levels below 10% of normal values reliably predict miscarriage. Additionally, elevated CA-125 levels, indicating decidual breakdown, can serve as a supportive diagnostic parameter.^【5】

Since continuation of the pregnancy is no longer possible, treatment aims to safely empty the uterus. Both medical and surgical interventions may be applied.

The most common method is uterine evacuation via suction curettage or sharp curettage after cervical dilation. Prior to the procedure, prostaglandin analogs such as misoprostol may be used to mature and dilate the cervix. Studies have shown that vaginal misoprostol effectively promotes cervical maturation, reduces intraoperative blood loss, and facilitates the procedure.

A diagnosis of inevitable miscarriage signifies the loss of the pregnancy and carries a negative prognosis. Biochemical tests performed during the threatened miscarriage phase, showing low levels of hPL and SP1, reliably predict progression to inevitable miscarriage. In these cases, pregnancy loss is certain; without intervention, the condition may progress to incomplete (incomplete) miscarriage or infection.

Various complications may arise during the process and treatment. The most common are hemorrhage and infection. Inadequate uterine contraction can lead to severe bleeding. During surgical evacuation, there is a risk of cervical injury or uterine perforation.

In cases not managed or performed under nonsterile conditions, the risk of infection increases, potentially leading to “abortus infeksiyozus,” characterized by pelvic pain, fever, and foul-smelling discharge. Additionally, the presence of a subchorionic hematoma is a factor that increases the risk of pregnancy loss and complicates the course.^【6】

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