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Basic Information ⬇

AUTHOR: Adrienne B. Neithardt, MD

Definition

Spontaneous abortion is fetal loss before wk 20 of pregnancy, calculated from the patient’s last menstrual period, or the delivery of a fetus weighing <500 g. Early loss is before gestational age 12 6/7 wk, whereas late loss refers to losses from wk 13 to 20.1

Spontaneous abortion can also be classified as incomplete (partial passage of fetal tissue through partially dilated cervix), complete (spontaneous passage of all fetal tissue), threatened (uterine bleeding without cervical dilation or passage of tissue), inevitable (bleeding with cervical dilation without passage of fetal tissue), or missed abortion (intrauterine fetal demise without passage of tissue).

Recurrent spontaneous abortion involves three or more spontaneous pregnancy losses before wk 20. It affects approximately 1% of couples attempting to conceive. However, in actual practice, most reproductive experts consider two spontaneous pregnancy losses sufficient to initiate an evaluation for habitual or recurrent spontaneous abortion, since the risk of another loss is similar at this point, and the emotional stress is high. As many as 5% of couples and probably even a higher proportion of couples in which the woman is over age 35 are affected by two or more consecutive spontaneous abortions.2

Synonyms

Spontaneous miscarriage

Miscarriage

Spontaneous pregnancy loss

ICD-10CM CODES
O03.89Complete or unspecified spontaneous abortion with other complications
O03.9Complete or unspecified spontaneous abortion without complication
Epidemiology & Demographics
Incidence

10% to 20% of clinically recognized pregnancies; 80% of miscarriages occur in the first trimester.1 Recurrent miscarriage occurs in <1% of couples attempting to have children.2

Risk Factors

  • Vaginal bleeding, which may have as high as a 50% chance of spontaneous abortion3
  • Advancing maternal age
  • Two or more prior miscarriages
  • Significant underlying maternal health issues such as uncontrolled diabetes, thyroid disease, or other endocrine disturbances4
  • Illicit substance use
  • Obesity
  • Alcohol, smoking, and excessive caffeine intake
  • Use of fluconazole in pregnancy is associated with a statistically significant increased risk of spontaneous miscarriage5
Genetics

  • Fetal chromosomal aneuploidy and polyploidy account for the overwhelming majority of first-trimester losses.1,2,6
  • Autosomal trisomy accounts for the majority of abnormalities, followed by monosomy X, tetraploidy, and, lastly, structural chromosomal abnormalities.6
  • The incidence of trisomy increases as maternal age increases.1,6
Maternal Causes

  • Uterine anomalies: Müllerian abnormalities such as unicornuate, bicornuate, or septated uterus are associated with increased miscarriage risk, although rates vary in different studies. A septated uterus is most highly associated with recurrent loss and can be surgically corrected and thus is important to diagnose.7 Other intrauterine pathologies such as synechiae, leiomyomas, or prior DES exposure are important to rule out also.
  • Incompetent cervix (iatrogenic or congenital, associated with 20% of midtrimester losses).
  • Antiphospholipid antibody syndrome.
  • Uncontrolled diabetes mellitus.4
  • Rare or controversial causes include HLA associations between mother and father; infections such as tuberculosis, Chlamydia, and Ureaplasma; smoking and alcohol use; irradiation; progesterone deficiency; and environmental toxins. Most of the literature is observational in nature, which may skew risk factor data.2,4,5
  • With two or more spontaneous miscarriages, a karyotype can be performed on the products of conception to evaluate for aneuploidy, which may be associated with a balanced translocation in one of the parents, and which has a substantially increased risk for abortion (depending on the actual type of translocation); if the pregnancy is carried to term, it has a 3% to 5% risk for an unbalanced karyotype.6 In patients with recurrent miscarriages, evaluation for anatomic defects such as uterine septum and for antiphospholipid syndrome (lupus anticoagulant, beta 2 glycoprotein IgG/IgM, and anticardiolipin antibody IgG/IgM) should also be obtained.2,4
Physical Findings & Clinical Presentation

  • Profuse bleeding and cramping have a higher association with miscarriage than bleeding without cramping, which is more consistent with a threatened miscarriage.
  • Cervical dilation with history or finding of fetal tissue at cervical os may be present.
  • In cases of missed abortion, uterine size may be smaller than menstrual dating, in contrast to molar gestation, where size may be greater than dates.
  • The presence of nausea and vomiting in early pregnancy is associated with a reduced risk for pregnancy loss.8
Etiology

In a general overview the etiology can be classified in terms of maternal (environmental) and fetal (genetic) factors, with the majority of miscarriages being related to genetic or chromosomal causes.

Diagnosis ⬆ ⬇

Differential Diagnosis

  • Normal pregnancy
  • Hydatidiform molar gestation
  • Ectopic pregnancy
  • Dysfunctional uterine bleeding
  • Pathologic endometrial or cervical lesions
Workup

  • All patients with bleeding in the first trimester should have an evaluation for possible ectopic pregnancy.
  • If there are three early, prior pregnancy losses, a workup and treatment for recurrent miscarriage should begin before next conception. If there is a strong history for second-trimester loss, consideration for cerclage should be given if the history is consistent with incompetent cervix (e.g., painless cervical dilation).
  • Most providers will initiate an evaluation for couples who have had two previous losses.
  • One unexplained fetal loss beyond 10 wk or 1 birth before 34 wk because of preeclampsia should prompt an evaluation for antiphospholipid antibody syndrome.
Laboratory Tests

  • Type and antibody screen are used to evaluate the need for Rh immune globulin.
  • Recurrent pregnancy loss: During the preconception period in patients with recurrent pregnancy loss, hemoglobin A1c, TSH, prolactin, anticardiolipin antibody, lupus anticoagulant, 20210A beta 2 glycoprotein antibodies, karyotyping, and anatomic evaluation with hysterosalpingography, or saline ultrasonography (2D/3D) to assess for uterine septum. With increasing age, oocyte quality is a factor, and some practitioners will perform day 3 of the menstrual cycle FSH and antimüllerian hormone to assess for diminished ovarian reserve. Progesterone level <5 mg/dl suggests nonviable gestation vs. >25 mg/dl, which suggests a good prognosis.2,6
Imaging Studies

Transvaginal sonogram (preferred) (Figs. 1, 2, and E3) can be used with menstrual dating and serum quantitative human chorionic gonadotropin to document pregnancy location, fetal heart presence, gestational sac size, and adnexal pathology.

Figure E3 Incomplete abortion.

Transvaginal ultrasonography shows an echogenic mass (arrows) in the fundal endometrial cavity. The lower-segment endometrium (arrowhead) is normal.

From Fielding JR et al: Gynecologic imaging, Philadelphia, 2011, Saunders.

Figure 2 Inevitable abortion.

Transvaginal ultrasonography shows a sac in the cervical canal, past the internal os. The embryo (curved arrow) was nonviable.

From Fielding JR et al: Gynecologic imaging, Philadelphia, 2011, Saunders.

Figure 1 Embryonic demise.

Transvaginal (A) and M-mode (B) ultrasound. There was no cardiac activity in an embryo measuring more than the threshold of 5 mm.

From Fielding JR et al: Gynecologic imaging, Philadelphia, 2011, Saunders.

Treatment ⬆ ⬇

Nonpharmacologic Therapy

Depending on the patient’s clinical status, desire to continue the pregnancy, and certainty of the diagnosis, expectant management can be considered. In pregnancies <8 weeks, complete expulsion of fetal tissue usually occurs, and surgical intervention such as D&C may be avoided especially if the women is symptomatic.1 However, expectant management is generally associated with longer time to resolution of pregnancy event and potentially higher risk of extensive blood loss and/or infection compared to surgical and/or medical management of a missed abortion.1

Acute General Rx

  • Incomplete miscarriage greater than 8 wk and especially in the second trimester can be associated with great blood loss; consideration should be given to D&C versus limited expectant or medical management based on the clinical presentation and patient’s wishes.
  • In cases of missed abortion, if fetal demise has occurred >6 wk before or gestational age is >14 wk, there is an increased risk of hypofibrinogenemia with disseminated intravascular coagulation. Thus D&C or manual vacuum aspiration should be performed early in the disease course. Consider use of misoprostol (Cytotec) in appropriate cases with or without pretreatment with mifepristone (200 mg orally) where the patient wishes to avoid surgery.1,9
  • There is evidence that a surgical approach leads to quicker resolution of the pregnancy event with fewer visits being required.1,8,10
  • Rh-negative patients should be given RhoGAM 50 mcg IM to prevent Rh isoimmunization.

Pearls & Considerations ⬆ ⬇

Spontaneous pregnancy loss is recommended as a replacement for the term abortion and to acknowledge the emotional aspects of losing a pregnancy.

Related Content

Miscarriage (Patient Information)

Related Content ⬆

    1. Early pregnancy lossObstet Gynecol. ;132(5):e197-207, 2018.
    2. Branch D.W. : Recurrent miscarriageN Engl J Med. ;363:1740-1747, 2010.
    3. Everett C. : Incidence and outcome of bleeding before the 20th week of pregnancy: prospective study from general practiceBMJ. ;315(7099):32-34, 1997.
    4. Hinkle S.N. : Association of nausea and vomiting during pregnancy with pregnancy lossJAMA Intern Med. ;176:1621-1627, 2016.
    5. Kaur R., Gupta K. : Endocrine dysfunction and recurrent spontaneous abortion: an overviewInt J Appl Basic Med Res. ;6(2):79-83, 2016.
    6. Ghosh J. : Methods for managing miscarriage: a network meta-analysisCochrane Database Syst Rev. ;2021(6), 2021.
    7. Molgaard-Nielsen D. : Association between use of oral fluconazole during pregnancy and risk of spontaneous abortion and stillbirthJ Am Med Assoc. ;315(1):58-67, 2016.
    8. Pinnaduwage L. : A comparison of the number of patient visits required for different management options for early pregnancy loss at an early pregnancy assessment clinicJOGC. ;40:1050-1053, 2018.
    9. Practice Committee of the American Society for Reproductive Medicine : Evaluation and treatment of recurrent pregnancy loss: a committee opinionFertil Steril. ;98(5):1103-1111, 2012.
    10. Practice Committee of the American Society for Reproductive Medicine : uterine septum: a guidelineFertil Steril. ;106(3):530-540, 2016.