Pregnancy loss before 20 weeks — most commonly first-trimester aneuploidy; expectant, medical, or surgical management.
Also known as: miscarriage, spontaneous abortion, missed abortion, incomplete abortion, threatened abortion, early pregnancy loss
Overview
Loss of a pregnancy before 20 weeks of gestation. Subtypes: threatened (vaginal bleeding with closed cervix and viable IUP), inevitable (bleeding with open cervix), incomplete (partial expulsion), complete (full expulsion), missed (fetal demise without expulsion), and septic abortion (infection complicating any of the above).
Epidemiology
~10-20% of clinically recognized pregnancies; ~50-60% if including biochemical losses. Most occur before 12 weeks. Recurrent pregnancy loss (≥2-3 consecutive losses) affects ~1-2% of couples.
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Environmental: high-dose radiation, certain teratogens
Pathophysiology
First-trimester losses are predominantly caused by fetal chromosomal abnormalities (~50%, most often autosomal trisomies, monosomy X, triploidy). Second-trimester losses more often relate to maternal anatomic, endocrine, immunologic, infectious, or cervical insufficiency causes.
Clinical presentation
Symptoms
Vaginal bleeding (light spotting to heavy hemorrhage)
Crampy lower abdominal/pelvic pain
Passage of tissue (clots, products of conception)
Loss of pregnancy symptoms (decreased breast tenderness, nausea)
Missed abortion may be asymptomatic — identified at routine ultrasound
Signs / physical exam
Speculum: open or closed cervix, blood, ± visible products of conception
Bimanual: uterine size (often smaller than dates), cervical dilation
Hemodynamic status — heavy bleeding can cause shock
Fever and uterine tenderness suggest septic abortion
Differential diagnosis
Ectopic pregnancy — Pain disproportionate to bleeding, no IUP on TVUS, abnormal β-hCG trend
Molar pregnancy — Markedly elevated β-hCG, hyperemesis, snowstorm on US
Implantation bleeding (viable IUP) — Light spotting, viable IUP on US, normal β-hCG rise
Subchorionic hematoma — Bleeding with viable IUP; hematoma on US; conservative management
Diagnostic workup
Labs
Quantitative serum β-hCG (declining or plateauing suggests nonviable)
CBC, blood type and Rh, antibody screen
Coagulation studies if heavy bleeding or suspected DIC (septic abortion)
Recurrent pregnancy loss workup: TSH, prolactin, A1c, antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, anti-β2GP1), parental karyotyping, hysterosalpingogram or sonohysterography for uterine anatomy
Imaging
Transvaginal ultrasound — gestational sac visible at β-hCG ~1500-2000, yolk sac ~5-6 weeks, fetal pole with cardiac activity ~6 weeks
Diagnostic criteria for early pregnancy loss (SRU 2013):
• Crown-rump length ≥7 mm without cardiac activity, OR
• Mean sac diameter ≥25 mm without embryo, OR
• Absence of embryo with heartbeat ≥2 weeks after a scan showing gestational sac without yolk sac, OR
• Absence of embryo with heartbeat ≥11 days after a scan showing gestational sac with yolk sac
Diagnostic algorithm
Subtype
Cervix
POC Expelled
US Findings
Management
Threatened
Closed
No
Viable IUP with bleeding
Expectant; repeat US
Inevitable
Open
No
Bleeding, dilation, viable or not
Expectant, medical, or surgical
Incomplete
Open
Partial
Retained products
Expectant, medical, or surgical (D&C)
Complete
Closed
Yes
Empty uterus, β-hCG falling
Confirm with β-hCG trend
Missed
Closed
No
Nonviable IUP retained
Medical or surgical (expectant slow)
Septic
Variable
Variable
Endometritis, retained products
IV antibiotics + prompt evacuation
Classification of spontaneous abortion subtypes.
Treatment
First-line
Counseling and shared decision-making among three options:
Expectant management (1-4 weeks for spontaneous completion) — ~80% effective for incomplete; lower (~30-50%) for missed
Medical management — misoprostol 800 mcg vaginally (with optional repeat dose); add mifepristone 200 mg PO 24 h before misoprostol for superior efficacy (combination preferred when available)
Surgical management — manual vacuum aspiration (in office for first trimester) or D&C (operating room); preferred if hemodynamically unstable, septic, severe bleeding, or patient preference
Anti-D immunoglobulin (RhoGAM) for Rh-negative women: 50 mcg if <12 weeks, 300 mcg if ≥12 weeks
Threatened abortion
Expectant management — bleeding stops in ~50% of cases with viable pregnancies
No proven benefit of bedrest or progesterone for sporadic loss (progesterone may help in recurrent loss)
Repeat ultrasound in 7-10 days to assess viability
Septic abortion
IV broad-spectrum antibiotics (clindamycin + gentamicin, or piperacillin-tazobactam)
Prompt surgical evacuation
ICU-level care; treat sepsis/DIC
Hysterectomy if uncontrolled infection
Recurrent pregnancy loss
Evaluate after 2-3 losses
Treat identified cause: levothyroxine for hypothyroidism, glycemic control, anatomic correction (resect septum), low-dose aspirin + heparin for APS
Genetic counseling for parental karyotype abnormalities; consider preimplantation genetic testing
Many cases remain idiopathic; ~60-70% achieve subsequent live birth with supportive care
Complications
Hemorrhage requiring transfusion
Retained products of conception → endometritis, secondary infection
Septic abortion → sepsis, DIC, ARDS, death
Asherman syndrome from aggressive curettage
Psychological grief, depression, anxiety
Rh isoimmunization in Rh-negative women without RhoGAM
PANCE pearls
Mifepristone + misoprostol combination is more effective than misoprostol alone for medical management of early pregnancy loss (PreFaiR trial); use the combination when mifepristone is available.
First-trimester pregnancy loss diagnostic criteria (Society of Radiologists in Ultrasound 2013) require definitive findings on TVUS — avoid premature diagnosis of nonviability.
All three management options (expectant, medical, surgical) have similar long-term outcomes — counsel based on patient preference and clinical factors.
Anti-D immunoglobulin is recommended for all Rh-negative women with pregnancy loss regardless of management approach.
Recurrent pregnancy loss workup begins after 2 (not 3) clinically recognized losses per ASRM 2020.
Provide grief counseling and follow-up — pregnancy loss has significant psychological impact.
References
ACOG PB 200 — ACOG Practice Bulletin No. 200: Early Pregnancy Loss
ASRM 2020 — Definitions of Infertility and Recurrent Pregnancy Loss: A Committee Opinion (Fertil Steril 2020)
SRU 2013 — Diagnostic Criteria for Nonviable Pregnancy Early in the First Trimester (Doubilet et al., NEJM 2013)
PreFaiR 2018 — Mifepristone Pretreatment for the Medical Management of Early Pregnancy Loss (Schreiber et al., NEJM 2018)
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