creation date: 2025-08-03 04:50
tags: Pathologies
Pregnancy Loss (Miscarriage)
Background
Definitions
Pregnancy loss, miscarriage, or spontaneous abortion refer to a nonviable intrauterine pregnancy up to 20 weeks gestation. The use of these terms in henceforth will use this definition.
Early pregnancy loss refers to loss during the first trimester. This often includes anembryonic pregnancies which refers to a gestational sac without an embryo (that was resorbed).
Embryonic demise refers to a visible embryo ≥7 mm without cardiac activity (<10 weeks) and fetal demise refers to a fetus without cardiac activity (≥10 weeks).
In cases where the miscarriage is complicated by uterine infection, the diagnosis is referred to as septic abortion.
At and beyond 20 weeks gestation, pregnancy loss is referred to as stillbirth. Induced abortion refers to the termination of a pregnancy without intent to result in a live fetus and refers to the procedure (not a diagnosis). Both of these are not discussed here.
Risk factors
Common risk factors for pregnancy loss include:
- Maternal age >35 years
- Increasing paternal age (unclear evidence)
- Past history of pregnancy loss (suggesting potentially inheritable component)
- Pollutants and toxins in environment
Maternal medical conditions:
- Infections
- Diabetes (type 1 and 2)
- Obesity
- Thyroid disease
- Stress
- Inherited thrombophilias and coagulation disorders
- Unintended pregnancy with IUD in place
- Subchorionic hematoma
Paternal medical conditions modesty increase risk, specifically components of metabolic syndrome.
Medication and drug exposure may affect pregnancy loss. A number of medications are considered teratogenic. Additionally, substances such as cigarettes, caffeine, and alcohol are associated with increased risk of pregnancy loss in a dose-response relationship.
Etiology
There are several causes for pregnancy loss:
- Chromosomal abnormalities - aneuploidy, partial deletion, or duplications are present in 70% of pregnancy loss.
- Maternal anatomic anomalies - fibroids, polyps, adhesions, or septa may be associated with pregnancy loss depending on the size and position.
- Trauma - especially direct impact to the uterus
In cases of second-trimester pregnancy loss, there are known and suspected etiology specific to this time frame:
- Infection
- Chronic stressors
- Uterine malformation
- Cervical insufficiency
- Fetal malformation
- Thrombophilias
- Abruption
- Premature preterm rupture of membranes
- Preterm labour
Clinical Presentation
Signs & Symptoms
The most common symptoms of pregnancy loss are:
- Uncomplicated bleeding (no or low risk of hemodynamic instability)
- Cramping/pain
In more complex causes:
- Hemorrhage (along with signs of severe blood loss)
- Infection (eg. purulent discharge, systemic signs)
In some cases, pregnancy loss may be found via tests and/or ultrasounds which would enable diagnosis in an asymptomatic patient
The expulsion of intrauterine tissue may also be occur prior to presentation.
History & Physical Exam
History should gauge symptoms as well as details on the pregnancy, including gestational age. In rare cases, patients may not have been aware they were pregnant and further questioning may be necessary.
Physical exam should be focused, including vital signs and assessment of hemodynamic stability.
Presence of peritoneal signs may suggest ectopic pregnancy and extra-uterine extensions may suggest septic abortion.
A pelvic exam including a speculum visualization of the cervix and bimanual palpation is needed for evaluation of miscarriage:
- Open or closed cervix
- Presence of pregnancy tissue within the cervical os
- Vaginal bleeding
- Signs of infection (purulent discharge, motion tenderness)
Diagnosis
Criteria
Complete pregnancy loss:
- No intrauterine pregnancy found (including all products of conception)
- Prior ultrasound confirming intrauterine pregnancy
Incomplete pregnancy loss:
- No intrauterine pregnancy found
- Open cervical os
- Evidence of product of conceptions in the vagina, in the discharged tissue collected by patient
Threatened pregnancy loss:
- Symptoms of pregnancy loss (bleeding and cramping) and bleeding is not from vaginal or cervical lesion
- Embryonic/fetal cardiac activity present
- Closed cervical os (not dilated or effaced)
Note, the term inevitable pregnancy loss, which refers to threatened pregnancy loss with an open cervical os, is not frequently used due to uncertainty.
Work-up
All suspected pregnancy loss is investigated with physical exam (including speculum exam) and ultrasound examination. The diagnosis is then made based on the combined findings.
Quantitative serum β-hCG ideally with trending, can assess viability.
In all cases, it is important to consider the possibility of heterotopic pregnancy with the loss of 1 gestation out of multiple.
In cases of miscarriage, evaluation of blood type and Rh alloimmunization risk may be necessary, although current evidence suggests this risk is not present in the first 12 weeks of pregnancy.
Differential
Alternative diagnoses depend on the physical exam and ultrasound findings.
Bleeding can occur from:
- Vaginal or cervical lesion
- Implantation bleeding (in early pregnancy)
In cases where no intrauterine pregnancy is observed on ultrasound, ectopic pregnancy is a possible diagnosis.
Red Flags / Complications
Complications include:
- Life-threatening hemorrhage
- Infection (septic abortion)
- Rh alloimmunization which can affect future pregnancies
- Incomplete uterine emptying
- Disseminated intravascular coagulation
Pregnancy loss may also be associated with psychological distress and counselling should be offered if necessary.
Management
The route of management is based on presence of complications, comorbidities, and patient preference.
Expectant management
Expectant management is generally effective for first trimester pregnancy loss. It is also the approach for threatened pregnancy loss.
Indications include:
- Gestational age <13 weeks (relative contraindication beyond first trimester)
- No antibiotic need
- Lack of comorbidities such as bleeding disorders
- Ability to follow-up repeat ultrasound to confirm completion of pregnancy loss
- Patients must be willing to wait up to 4-8 weeks for resolution.
Pain management with NSAIDs are typically sufficient. Follow-up should occur every 1-2 weeks until completion and alternative management plans should be considered/implemented if pregnancy has not passed in >4 weeks.
Medical management
Use of medications can expedite the resolution of pregnancy loss.
Similarly to expectant management, patient’s that cannot tolerate heavier bleeding should not use this route of management. Similarly, need for antibiotics should not use medical management.
For first trimester pregnancy loss, the regime is:
- Mifepristone 200 mg PO
- Misoprostol 800 mcg vaginally, buccally, or sublingually 24 hours after mifepristone
For patients <10 weeks pregnant and minimal or no bleeding was seen after initla dose, a repeat dose of misoprostol is administered after around 24 hours (range: ≥3 hours but <7 days).
For patients ≥10 weeks pregnant, additional dose after 3 months improves outcome (same range). Continued repeated doses q3h can be considered until expulsion.
For second trimester pregnancy loss, the regime is:
- Mifepristone 200 mg PO
- Misoprostol 400 mcg vaginally, bucally, or sublingually 24 hours following mifepristone and repeated q3-6h until expulsion.
In cases where ≥1 uterine scar (and thus increased risk of uterine rupture), misoprostol should be administered 200 mcg q3h instead.
If mifepristone is unavailable or patient prefers misoprostol-only management, misoprostol can be used as monotherapy.
Follow-up should confirm completed pregnancy loss by ultrasound or serial serum hCG.
Surgical management
Surgical/interventional management of pregnancy loss consist of uterine aspiration. This is typically done by manual uterine aspiration using manual vacuum aspiration device or electric vacuum aspiration.
For second trimester pregnancy loss, use of grasping forceps in conjunction with suction is typical, referred to as dilation and evacuation.
In cases of septic abortion, surgical management is used following stabilization by IV fluids. Empiric IV antibiotic regime are also used. Examples include:
- Ampicillin 2g IV q4h, gentamicin 5 mg/kg daily IV, and metronidazole 500 mg IV q8h
- Piperacillin tazobactam 4.5 g IV q8h with or without vancomycin