What is the management plan for a pregnant patient with a threatened miscarriage?

Management of Threatened Miscarriage

For women with threatened miscarriage (vaginal bleeding with closed cervix in early pregnancy), progesterone supplementation does not improve live birth rates in the general population and should not be routinely used, though vaginal micronized progesterone 400 mg nightly may be considered for women with both current bleeding AND one or more prior miscarriages. 1, 2

Initial Assessment

When a pregnant patient presents with vaginal bleeding and/or cramping:

• Confirm viability and gestational age using transvaginal ultrasound to visualize fetal cardiac activity and measure crown-rump length 3
• Assess cervical status through speculum examination—threatened miscarriage is defined by a closed cervical os; an open os indicates inevitable or incomplete miscarriage 3, 4
• Evaluate bleeding severity including amount, duration, and presence of clots or tissue 3
• Check for signs of ectopic pregnancy including unilateral pain, adnexal mass, or free fluid on ultrasound 4

Risk Stratification

Higher risk features that predict progression to miscarriage include:

• Heavy vaginal bleeding (soaking through pads) 3
• Maternal age >35 years (OR 1.85 for miscarriage) 5
• Low serum progesterone (<35 nmol/L) associated with 70.8% miscarriage rate 6
• Empty gestational sac >15-17 mm diameter without visible embryo 3
• Early gestational age (<6-7 weeks) 3

Evidence-Based Treatment Approach

Progesterone Therapy Decision Algorithm

For women WITHOUT prior miscarriages:

• Do not prescribe progesterone—high-certainty evidence shows no benefit (RR 0.99,95% CI 0.95-1.04) 1
• Live birth rates are 82-84% with or without progesterone treatment 2

For women WITH one or more prior miscarriages AND current bleeding:

• Consider vaginal micronized progesterone 400 mg nightly until 12 weeks gestation 1
• This increases live birth rate (RR 1.08,95% CI 1.02-1.15) compared to placebo 1
• However, one recent trial found no benefit even in this subgroup (RR 0.95% CI 0.82-1.11), creating equipoise 2
• Given conflicting evidence, shared decision-making is appropriate for this specific population 1, 2

Alternative progestogen formulations:

• Dydrogesterone shows no clear benefit (RR 0.98,95% CI 0.89-1.07) 1
• 17-α-hydroxyprogesterone and oral micronized progesterone lack sufficient data 1

Interventions NOT Recommended

• Bed rest—commonly prescribed but lacks evidence of benefit 3, 4
• Human chorionic gonadotropin (hCG) supplementation—insufficient evidence 3, 4
• Routine hospitalization—not indicated for stable threatened miscarriage 3

Monitoring and Follow-Up

• Repeat ultrasound in 7-14 days to confirm ongoing viability if initial scan shows cardiac activity 3
• Serial serum progesterone or hCG levels can help prognosticate but do not change management 3, 6
• Counsel patients that approximately 15-20% of clinically recognized pregnancies end in miscarriage, with 50-60% due to chromosomal abnormalities 4

Critical Pitfalls to Avoid

• Do not prescribe progesterone universally—the majority of women (those without prior losses) receive no benefit 1, 2
• Do not delay evaluation for ectopic pregnancy—threatened miscarriage presentation can overlap with ectopic pregnancy 4
• Do not attribute all first-trimester bleeding to threatened miscarriage—consider molar pregnancy, cervical pathology, and subchorionic hematoma 4
• Recognize that most miscarriages result from chromosomal abnormalities—treatment cannot prevent genetically abnormal pregnancies from miscarrying 4

Safety Considerations

When progesterone is used:

• Congenital abnormalities show no increase (RR 1.00,95% CI 0.68-1.46) 1
• Adverse drug events are not significantly increased (RR 1.07,95% CI 0.81-1.39) 1
• Preterm birth rates are similar between progesterone and placebo groups 2

When to Consider Alternative Diagnoses

If bleeding persists or worsens despite apparent viability:

• Subchorionic hematoma—visible on ultrasound, generally benign 4
• Cervical pathology—polyps, ectropion, or malignancy 4
• Molar pregnancy—"snowstorm" appearance on ultrasound, markedly elevated hCG 4