Threatened Abortion

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Continuing Education Activity

A threatened abortion is vaginal bleeding during pregnancy that does not meet diagnostic criteria for spontaneous abortion. In a threatened abortion, the cervical os remains closed. The World Health Organization (WHO) defines a threatened abortion as pregnancy-related bloody vaginal discharge or frank bleeding during the first half of pregnancy without cervical dilatation. A threatened abortion can present during early pregnancy with lower abdominal pain, and/or vaginal bleeding. Nearly 25 percent of pregnant women have some degree of vaginal bleeding during the first two trimesters and about 50 percent of these progress to an actual abortion. The bleeding in a threatened abortion is mild to moderate. The abdominal pain may present as intermittent cramps, suprapubic pain, pelvic pressure, or lower back pain. This activity examines when this condition should be considered on differential diagnosis and how to properly evaluate it. This activity highlights the role of the interprofessional team in caring for patients with this condition.


  • Outline threatened abortion.
  • Summarize the differences between threatened abortion and other abortion types including elective, inevitable, incomplete, complete, or missed.
  • Explain how to manage a patient presenting with a threatened abortion.
  • Describe how the facilitation of interprofessional team education and discussion can optimize the effective detection of a threatened abortion and inform the need for subsequent evaluations.


Abortion is the medical term for a pregnancy loss before 20 weeks of gestational age.  The types of spontaneous abortion include threatened, inevitable, incomplete, complete, septic, and missed abortion[1].  

A threatened abortion is defined as vaginal bleeding before 20 weeks gestational age in the setting of a positive urine and/or blood pregnancy test with a closed cervical os, without passage of products of conception and without evidence of a fetal or embryonic demise. The definition of a threatened abortion by the World Health Organization (WHO) is pregnancy-related bloody vaginal discharge or frank bleeding during the first half of pregnancy without cervical dilatation[2].

Other types of abortion should be considered if the cervical os is open, if there is determined to be an extrauterine pregnancy, if there is determined to be an intrauterine pregnancy without a fetal heartbeat, or if there is evidence of the passage of products of conception[3].

Nearly 25% of pregnant women have some degree of vaginal bleeding during the first two trimesters and about 50% of these progress to loss of the pregnancy. The bleeding during a threatened abortion is typically mild to moderate. The abdominal pain may present as intermittent cramps, suprapubic pain, pelvic pressure, or lower back pain. [4][5][6][7]


The exact etiology of a threatened or spontaneous abortion is not always known.  It is widely accepted that the vast majority of spontaneous abortions cannot be prevented or modified likely because they are due to chromosomal abnormalities in at least half of all cases[8]. For pregnancy losses that are determined to have a normal chromosomal makeup, termed euploid abortions, maternal and paternal factors play a more significant role[9]. Optimization of maternal health before pregnancy, correcting structural abnormalities of the uterus, and minimizing exposure to teratogens or infections during early pregnancy can reduce the risks for spontaneous abortion[10]. When optimizing maternal health, special consideration should be given to chronic illnesses such as diabetes and thyroid disease, as well as extremes of weight and use of tobacco products, alcohol, or illicit drugs.  Some studies have shown that folic acid supplementation immediately before and during early pregnancy may reduce the risk of spontaneous abortionf[11]. It has also been shown in several studies that increasing paternal age is associated with increased risk for pregnancy loss, likely due to increased chromosomal abnormalities[12]. Women should also be educated about reducing the risk of traumatic events and should be screened for risk for intimate partner violence. It is reasonable to recommend preconception counseling to modify these risk factors. [6][13][14][15]


Threatened abortion can occur in any pregnancy regardless of maternal age, race, comorbidities, lifestyle, or socioeconomic status[10]. If a woman has previously had bleeding in the first trimester of pregnancy, her risk of bleeding in the first trimester of subsequent pregnancies does appear to be increased. Risk factors for any type of miscarriage include advanced maternal age, advanced paternal age, prior history of pregnancy loss, TORCH infections, uncontrolled hyperglycemia, obesity, uncontrolled thyroid disease, significant stressors, use of teratogenic medications, and presence of a subchorionic hemorrhage[12]


A threatened abortion occurs when a pregnant patient at less than 20 weeks gestation presents with vaginal bleeding. The cervical os is closed on a physical exam. The patient may also experience abdominal cramping, pelvic pain, pelvic pressure, and/or back pain. Vaginal bleeding usually begins first followed by cramping abdominal pain hours to days later. Bleeding is the most predictive risk factor for pregnancy loss. More than half of threatened abortions will abort. The risk of spontaneous abortion, in a patient with threatened abortion, is less if fetal cardiac activity is present[1]


It is strongly recommended that all products of conception from any type of abortion are considered for histopathological examination.  For patients with repeat pregnancy loss, karyotyping should be given as an option for products of conception to rule in or rule out chromosomal abnormalities as likely cause of spontaneous abortion.  This information can help patients determine the best options for moving forward if they desire future pregnancies[16].

History and Physical

A pelvic exam is mandatory to determine the type of abortion. Determining factors include the amount and site of bleeding, whether the cervix is dilated, and whether fetal tissue has passed. In a threatened abortion, the vaginal exam may reveal a closed cervical os with no tissue. There is usually no cervical motion tenderness[17]. In rare cases, the pelvic exam will reveal uterine and bilateral adnexal tenderness. It is important to note that in a threatened abortion there is no passage of tissue and the cervical os is, by definition, closed[2]. These observations differentiate the condition from an inevitable or incomplete abortion. Women with a threatened abortion usually have stable vital signs, but if hypovolemia is present, one should suspect bleeding or sepsis. The abdomen in most cases is non-tender and soft. If it is confirmed that there is no viable fetus, a discussion concerning expectant management or induction of abortion should occur with the patient. The method of inducing abortion is either surgical with a suction dilation and curettage or medical with a medication like misoprostol[18][19]


The diagnosis is made by history, physical exam, measurement of beta-human chorionic gonadotropin (beta-hCG), and an ultrasound[10]

A thorough history should be obtained including pregnancy history, medical history, and history of present illness. History of present illness should include when and how symptoms/bleeding began, modifying factors, any treatments trialed up to the point of evaluation, and helping the patient to describe and quantify the bleeding[20][5]

Transvaginal ultrasound may be used to locate the pregnancy and determine if the fetus is viable. The ultrasound can also help rule out ectopic pregnancy and to evaluate for retained products of conception. A yolk sac is typically seen at 36 days, and a heartbeat is seen on ultrasound at approximately 45 days after the last menstruation[21].

A beta-hCG level of 1500 lU/mL to 2000 lU/mL is associated with a gestational sac on ultrasound. Beta-hCG doubles in 48 hours in 85% of intrauterine pregnancies. Beta-hCG is usually detectable the first nine to 11 days following ovulation and reaches 200 IU/mL at the expected time of menses[22].

Rh factor will also determine if Rhogam should be administered to prevent hemolytic disease of the newborn in this pregnancy and subsequent pregnancies[23].

Hemoglobin and hematocrit levels help monitor the degree of blood loss. 

A urinalysis can also be obtained. Urinary tract infection (UTI) has been associated with signs and symptoms of threatened abortion[24].

During the pelvic exam, suction or cotton swabs may be needed to remove blood and products of conception to allow for better visualization of the cervix. Ringed forceps can also be used to remove tissue that may be protruding from the cervical os. All tissue must be examined to determine if it is a clot or products of conception. Evidence of products of conception protruding from the cervix or within the vagina changes the diagnosis from a threatened abortion to a complete or incomplete abortion. Evaluation of the amount of bleeding/blood loss should be performed through a thorough history, as well as during the pelvic examination[25]

Treatment / Management

Alloimmunization prevention by the administration of Rh(D) immunoglobulin should be considered for patients who have vaginal bleeding in the setting of pregnancy in a patient who is Rh-[26].  It has been determined that a 50 mcg dose of immunoglobulin is effective at alloimmunization prevention up to and through the 12th week of gestation, however, it is considered acceptable to give the standard 300 mcg dose due to availability or provider preference[23].

Patients with a threatened abortion should be managed expectantly without any medical or surgical interventions. However, patients should be given strict return precautions concerning excessive vaginal bleeding, abdominal pain, or fever and patients should be educated on the importance of follow-up. Analgesia can be provided to help relieve discomfort from cramping. NSAIDs should be avoided in the setting of a threatened abortion, as the pregnancy may continue to progress to viability[27]. Follow-up is recommended with serial transvaginal ultrasounds until a viable intrauterine pregnancy is confirmed or until progression to an inevitable, incomplete, or complete abortion occurs.  Clinicians can consider serial quantitative beta hCG testing as recommended for a pregnancy of unknown origin to continue to monitor for the viability of the pregnancy, especially in the setting where an intrauterine pregnancy with cardiac activity has not been confirmed by ultrasound[28].  In these cases, it is possible that the pregnancy has not reached the gestational age by which cardiac activity would be expected on ultrasound or it is possible that the pregnancy will not be viable[22].  The patient should be counseled about the possibility of spontaneous abortion of the pregnancy, as well as the possibility that the pregnancy may continue to progress towards viability.  Several trials have shown that progesterone supplementation does not improve outcomes for patients with threatened abortion and progesterone is not currently recommended as treatment or prevention for patients with threatened abortion.[29]  Bedrest and other activity restrictions have not been found to be efficacious in the prevention of a threatened abortion progressing to spontaneous abortion and have been shown to increase the risk of other complications including deep vein thrombosis and/or pulmonary embolism and therefore should not be recommended[30].  Some providers do prefer to advise patients to avoid strenuous activities and to maintain pelvic rest at least until the cessation of vaginal bleeding. Clinicians should recommend that patients start or continue to take prenatal vitamins with folic acid supplementation. [31][32][33][34]

Differential Diagnosis

Clinicians should consider several differential diagnoses when encountering vaginal bleeding in the setting of pregnancy. Vulvar, vaginal, cervical trauma should be ruled out during a pelvic examination.  Cervical friability can lead to vaginal bleeding which can be caused by cervicitis from an infection or due to premalignant or malignant changes on the cervix. Clinical judgment should determine whether or not the patient should undergo a Pap smear and/or cultures for infection at the time of examination. Other types of abortion should be considered including elective, inevitable, incomplete, complete, septic, and missed abortion[25]


Studies have shown that about 20% of women experience vaginal bleeding before 20 weeks of pregnancy. Furthermore, about 50% of those patients who experience a threatened abortion progress to a pregnancy loss. Studies have shown that there may be an increased risk of adverse outcomes later in pregnancy if there was vaginal bleeding during the first trimester of that pregnancy. For example, there may be a greater risk of placenta previa, placental abruption, necessitation for manual removal of the placenta after delivery, cesarean delivery, preterm premature ruptured membranes, preterm birth, low-birthweight infant, fetal-growth restriction, and fetal or neonatal death. [2]


  • Pregnancy loss (progression to inevitable, incomplete, complete, missed abortion)
  • Heavy bleeding
  • Retained products of conception
  • Endometritis
  • Septic abortion 
  • Complications later in pregnancy as discussed in "Prognosis" [20]


Patients with recurrent pregnancy loss or recurrent bleeding during pregnancy should be offered evaluation by a reproductive endocrinology and infertility specialist and/or by a maternal-fetal medicine specialist. If a patient is determined to have a coagulopathy, a hematology consult should be considered[10]

Deterrence and Patient Education

Patient education should be provided as both verbal and written explanations and instructions. It should be explained to the patient that it is possible her pregnancy will continue and it is also possible that she will undergo a miscarriage. The patient needs to understand that the vast majority of miscarriages are not preventable and that she is not at fault for the loss of the pregnancy if a loss does occur[35]. Providers should explain to the patient that mild to moderate bleeding and cramping can be expected, but uncontrolled pain or heavy bleeding should be evaluated by an obstetric care provider or in the emergency department. Many providers explain that saturating more than 1-2 pads per hour for 2 hours is considered to be heavy bleeding and should be promptly evaluated[36]. Patients can be instructed to take acetaminophen as directed for pain relief. Patients should avoid ibuprofen for pain control during a threatened abortion as it is contraindicated in pregnancy and the patient's pregnancy may progress to viability. Patients who undergo threatened abortion should be evaluated for mood disorders including depression and anxiety. Especially if a threatened abortion proceeds to pregnancy loss, the patient should be allowed to grieve as appropriate for each individual and should be offered grief counseling[37].

Pearls and Other Issues

Most patients with a threatened abortion can be observed from home with close follow-up. Repeat ultrasounds and beta-hCG levels will help to determine progression to a viable pregnancy or to an inevitable, complete, incomplete, or missed abortion. Patients with increased vaginal bleeding require evaluation for hemorrhagic anemia and may be candidates for a blood transfusion or pregnancy evacuation[38]

Enhancing Healthcare Team Outcomes

The diagnosis and management of a threatened abortion involve an interprofessional team that can include an emergency department physician, obstetrician, radiologist, midlevel providers, and nursing staff.  For patients to be safely monitored expectantly, good communication between clinicians and the patient is key. All members of the care team need to be on the same page regarding the possibility of pregnancy loss and the importance of return precautions[39].  

Article Details

Article Author

MIchelle Mouri

Article Author

Heather Hall

Article Editor:

Timothy Rupp


9/9/2021 12:31:00 AM

PubMed Link:

Threatened Abortion



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