What is the management of threatened abortion?

Management of Threatened Abortion

Threatened abortion should be managed with transvaginal ultrasound to confirm fetal viability, followed by progesterone supplementation (200 mg vaginal micronized progesterone twice daily until 12 weeks gestation) in women with prior miscarriage history, and anti-D immunoglobulin (50 μg) for all Rh-negative women with documented pregnancy loss. 1, 2

Initial Diagnostic Evaluation

Transvaginal ultrasonography is the diagnostic method of choice to confirm fetal viability, detect subchorionic hematoma, and rule out ectopic pregnancy or other complications 1. Do not delay ultrasound imaging based on β-hCG levels below a discriminatory threshold, as ectopic pregnancies can present at almost any β-hCG level and rupture has been documented at very low levels 1.

Key Clinical Assessment Points

• Perform speculum examination to identify the source of bleeding and assess cervical status (closed cervix confirms threatened abortion versus open cervix indicating inevitable abortion) 1
• Evaluate for alternative diagnoses including ectopic pregnancy, ovarian torsion, or pelvic inflammatory disease through complete pelvic examination 1
• Serial β-hCG measurements can confirm pregnancy loss when diagnosis is uncertain, with levels that fail to rise appropriately or decrease indicating loss 3

Progesterone Therapy

For women with prior miscarriage history and current threatened abortion, prescribe vaginal micronized progesterone 200 mg twice daily 2. The evidence shows this probably reduces miscarriage risk (RR 0.64,95% CI 0.47 to 0.87) 2.

Critical Treatment Parameters

• Stop progesterone at 12 weeks gestation, not 16 weeks as recommended by some guidelines, because progesterone's beneficial effects are complete by 12 weeks when the placenta takes over progesterone production 4
• Oral progesterone (200 mg twice daily) is also effective and probably reduces miscarriage rate (RR 0.57,95% CI 0.38 to 0.85) 2
• Higher doses of progesterone create a more favorable anti-inflammatory environment by reducing IL-6 and TNF-α while increasing IL-10 5

Important Caveats

• Progesterone treatment does not increase risk of pregnancy complications, preterm birth, or low birth weight 6
• The evidence on congenital abnormalities is uncertain and based on very low-quality evidence 2
• Do not use progesterone indiscriminately—treatment is only reasonable when the fetus is not seriously affected, as it would not be beneficial to permit chromosomally or anatomically abnormal embryos to survive to term 7

Rh Immunoglobulin Prophylaxis

Administer 50 μg of anti-D immunoglobulin to all Rh-negative women with documented first-trimester pregnancy loss to prevent Rh-D alloimmunization 1, 3. This is critical because fetomaternal hemorrhage occurs in 48% of threatened abortion cases and 32% overall in spontaneous abortion 1.

Nuanced Approach to Viable Pregnancies

• For threatened abortion with a viable fetus, there is no evidence-based recommendation for anti-D immunoglobulin administration, and many physicians do not treat when there is a live embryo or fetus 1
• However, given the high rate of fetomaternal hemorrhage (48% in threatened abortion), consider administration even with viable pregnancy on a case-by-case basis 1

Follow-Up and Monitoring

• Perform serial ultrasound examinations to assess fetal growth and development in women who continue pregnancy after threatened abortion 1
• Provide immediate contraceptive counseling if pregnancy loss occurs, as ovulation can resume within 2-4 weeks post-abortion 3
• Combined hormonal contraceptives or implants can be initiated immediately after complete abortion without waiting for next menses 3

Red Flags Requiring Urgent Intervention

Watch for signs of infection that require immediate action, even without fever present 3:

• Maternal tachycardia
• Purulent cervical discharge
• Uterine tenderness
• Fetal tachycardia (if fetus still viable)

If infection is suspected, initiate broad-spectrum antibiotics immediately and proceed with urgent surgical evacuation 3. Do not wait for fever to develop, as clinical symptoms of infection may be less overt at earlier gestational ages 3.

When to Abandon Expectant Management

Expectant management is absolutely contraindicated in the following scenarios 3:

• Confirmed fetal demise (requires active evacuation)
• Profuse vaginal bleeding (requires urgent surgical evacuation)
• Signs of intrauterine infection
• Hemodynamic instability

Expectant management carries significantly higher maternal morbidity (60.2% versus 33.0% with active management), with intraamniotic infection occurring in 38.0% of cases and postpartum hemorrhage in 23.1% 3.