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Incomplete Abortions

Editor: Hao Nguyen Updated: 6/27/2022 11:49:10 PM

An incomplete abortion is a subtype of spontaneous abortion, along with inevitable and missed abortion. Other types of spontaneous abortion are threatened abortion and complete abortion. This article will focus on incomplete abortion, which is described as partial loss of products of conception within the first 20 weeks of pregnancy. Patients will present with vaginal bleeding with lower abdominal and/or pain and cramping. Threatened abortion is vaginal bleeding with a closed cervical os and viable pregnancy. Inevitable abortion is vaginal bleeding with an open cervical os and viable pregnancy. Complete abortion is vaginal bleeding with either an open or closed cervical os with complete loss of products of conception. 

The overall incidence of spontaneous abortion is 10% to 15%. It is divided into early, <12 weeks, and late, >13 weeks.[1] The causes of abortion are usually unknown but most commonly are attributed to fetal chromosomal abnormalities and the rest due to modifiable etiologies and risk factors. Treatment of incomplete abortion includes expectant, medical, and/or surgical treatment.[2] Complications are rare but can be serious such as sepsis from the retained product, hemorrhagic shock, and uterine rupture. The prognosis for these patients is generally good with a proper workup, close obstetric follow-up, and patient education.


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In general, incomplete abortions are not preventable, in which 50% of cases are from chromosomal abnormalities.[3] Other cases are due to modifiable etiologies and risk factors such as age, maternal diseases (diabetes, hypertension, renal disease, thyroid issue, polycystic ovary syndrome, lupus, thrombophilia), under or overweight, abnormal uterine, teratogen exposure (drug, alcohol, caffeine, radiation), and infections (human immunodeficiency virus, sexually transmitted infections, Listeria monocytogenes). Consequently, some of the modifiable etiologies or risk factors may result in congenital anomalies, which can cause incomplete abortion.

Other less known and reported cases are from prior elective medical or illegal abortions, poor or no prenatal care, and lower abdominal or pelvic trauma.[1][4][5] Higher cases are reported in third world countries where abortion is prevalent and in women who live in areas where elective abortion is illegal, and in those with poor access to healthcare.[6][7]

Incomplete abortions occur in women that are <20 weeks pregnant. They occur more frequently in women with advanced maternal age and women with lower socioeconomic status or those who engage in risky behaviors. The risk factors and patient population most commonly affected mimic those of spontaneous abortion. Women in third-world countries or those who live in areas with poor access to healthcare are also at increased risk of incomplete abortions after a medically or surgically induced abortion.[6] 

Women who have been diagnosed with hydatidiform moles, typically aged 15 to 20 years old, have a 13% chance of incomplete abortion.[8] No statistical data exists worldwide due to the legalization of abortion in many countries and underreporting of cases in third world countries.

History and Physical

A complete history of modifiable etiologies and risk factors is important. Ascertain about prenatal care and the date of the last menstrual cycle and calculate the due date. This is crucial because the further along the fetus, the more complications will develop, and intervention may be more surgical than expectant or medical treatment. The amount of bleeding and evaluation for ongoing bleeding should be elicited, as well as if any tissue or clots have been passed. Saturating more than one pad an hour suggests heavy bleeding and requires emergent attention. A large amount of blood clots also is indicative of heavy bleeding.

Cramping is rhythmic similar to labor, but less intense. Obtain and monitor vital signs frequently for early signs of shock from blood loss. A fever is concerning for infection and possible septic abortion, which requires emergent surgical intervention. An incomplete abortion usually presents with moderate to severe vaginal bleeding and is frequently accompanied by lower abdominal and/or pelvic pain that is suprapubic, which may radiate to the lower back, buttocks, genitalia, and perineum.

In almost all cases, the pelvic exam will reveal an open cervical os with products of conception readily visible. There may have already been the expulsion of some fetal tissue.[2] In rare cases, the cervical os will be closed, but there may still be some conception fragments seen. Cervical shock can occur if there is too much vagal stimulation at the cervix caused by the incomplete passage of products of conception; this can present with bradycardia and hypotension that does not respond to IV fluids.[9] Gross examination of aborted products should be done and sent for histopathological examination.


The ideal method of diagnosing an incomplete abortion is to obtain a quantitative human chorionic gonadotropin (hCG) level and transvaginal or transabdominal ultrasound.[2] The ultrasound will usually reveal the presence of some products of conception in the uterus. The hCG levels will be low, and there will not be any fetal heartbeat.[4] A bimanual exam will usually reveal a large but soft uterus. Other laboratories include a complete blood count, type and cross match, Rh factor, and coagulation profile.

Treatment / Management

Incomplete abortions are most commonly treated expectantly with frequent obstetrics follow-up and serial quantitative beta-hCG levels. Most of these women will expel the fragments of conception on their own without the need for further medical or surgical treatment.[2] However, in some instances, IV hydration and pain medication may be required. If the bleeding is severe, there may be a need for blood transfusions. Patients should be admitted for ongoing blood loss and monitored for shock and possible surgical evacuation.

In patients with conception fragments at the cervical os, a clinician can remove the fragments with forceps to help initiate the process of hemostasis, facilitate uterine contractions, and decrease vagal stimulation.[9] This will prevent cervical shock.

It is important to remember that females who are Rh-negative require RhoGAM. Some obstetricians will manage incomplete abortions medically with oxytocin to help control the bleeding and misoprostol to help the uterus contract and complete the process of abortion. Surgical management with dilation and curettage is another treatment modality that may be utilized but is normally reserved for unstable patients.

Differential Diagnosis

Differential diagnoses for lower abdominal and/or pelvic pain with vaginal bleeding in a pregnant female include ectopic pregnancy, idiopathic bleeding in a viable pregnancy, subchorionic hemorrhage, molar pregnancy, vaginal trauma, vaginal or cervix infection, spontaneous abortion, or cervical abnormalities (excessive friability, malignancy, or polyps).[4] If the patient presents with signs of shock, the differential can widen to include septic abortion, hemorrhagic shock, cervical shock, or uterine rupture.[9]


Patients with incomplete abortion normally have a good prognosis and can be managed expectantly with an 82% to 96% success rate with no future consequences on fertility.[4][10] There were shown to be no major differences in medical versus expectant management of incomplete abortion when gestation age is less than 12 weeks. Avoiding surgery has also been shown to be beneficial as there are fewer adverse events. 

Incomplete abortions after 12 weeks have a 3.4% increased risk of unfavorable outcomes, including maternal death, major surgery, or sterility. This is likely secondary to the increases in the fetus size, blood supply, and uterine size. After 14 weeks of gestation, there is an even further increased risk of maternal death and serious complications. Another risk factor for poor prognosis is delayed time to seeking treatment, which can be seen in rural and poor communities where healthcare is sparse.[6]


Complications include severe hemorrhage or sepsis from an incomplete septic abortion. Prompt surgical management is indicated when the patient is unstable. It is also important to rule out ectopic pregnancy, presenting with vaginal bleeding and lower abdominal and/or pelvic pain.[4] There are several other complications that can arise after the management of incomplete abortion including death, uterine rupture, uterine perforation, subsequent hysterectomy, multisystem organ failure, pelvic infection, cervical damage, vomiting, diarrhea, infertility, and/or psychological effects.

Patients can present with different forms of shock, including hemorrhagic, septic, and cervical. Infection following an incomplete abortion is low. In low-income countries where females had surgical management of incomplete abortion, the infection rate was 0.1% to 4.7%, whereas it was only 0.1% to 0.5% in high-income countries. Infection is secondary to retained products of conception and can be the result of various bacteria, the most common being genital flora (group B strep, B. fragilis, and E. coli).[11]


A patient who presents with unstable vitals and heavy bleeding with abnormal hemoglobin will need emergent obstetric evaluation and possible intervention. Stable patients will need urgent obstetric consultation to help manage and secure close follow-up for the patient. In many instances, the patient will need to follow up for repeated quantitative beta-hCG levels, and if needed, for further medical or surgical treatment. Patients also will need to follow up with obstetrics for contraception following an abortion.

Deterrence and Patient Education

First trimester bleeding is present in 20% to 25% of pregnancies, half of these women will go on to have a spontaneous abortion. An incomplete abortion is the incomplete expulsion of fetal products. Patients should not delay seeking medical care if they experience bleeding during pregnancy, as this can lead to increased morbidity and mortality.[6] After a woman is evaluated by a medical professional and diagnosed with incomplete abortion, a treatment plan will be decided upon based on patient presentation.

The most common management is expectant, and women can expect to continue bleeding for 1-2 weeks. Obstetric follow-up is very important for a repeat ultrasound and serial beta-hCG levels to ensure all conception products have been expelled completely. It is also important to educate patients that uncomplicated abortions have no impact on future fertility, and ovulation can occur as soon as eight days after the expulsion of fetal tissues.[10]

Pearls and Other Issues

If there are no complications, patients can be discharged after observation. Patients with hemodynamic instability, low hemoglobin, and ongoing vaginal bleeding need to be admitted. A repeat ultrasound and down-trending quantitative beta-hCG are required to ensure that no products of conception have been retained.

Enhancing Healthcare Team Outcomes

Management of patients with incomplete abortion requires a full interprofessional healthcare team as soon as the patient presents. She will need nursing, laboratory technicians, radiology, pharmacists, and other specialists such as obstetrics and psychiatry. IV lines need to be placed, and blood work such as beta-hCG, blood type with Rh, complete blood count, and complete metabolic panel. In addition, she will likely need IV fluids and medicine for pain or nausea.

A pelvic ultrasound determines fetal viability versus the presence or absence of fetal tissues. Consultation to obstetrics will be done while the patient is in the emergency department, and this will help with the patient disposition and follow-up. Consultation should be placed to psychiatry after the abortion is completed to manage feelings of guilt, depression, anxiety, grief, and post-traumatic stress disorder that can be common.[12] These patients tend to do better psychologically if they have an active role in their treatment plans. Women who were active participants in the treatment plan for incomplete abortion (i.e., expectant, medical, or surgical management) had better mental health outcomes than their cohorts who were not active in the treatment plan at 12 weeks postpartum.[13]



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