What should progesterone levels be during pregnancy?

Progesterone Levels During Pregnancy

Progesterone levels vary significantly by clinical context, but for assessing first-trimester viability in symptomatic women, levels below 6.3 ng/mL strongly suggest non-viable pregnancy (>90% predictive), while levels above 20-25 ng/mL indicate viable pregnancy in over 90% of cases.

Diagnostic Thresholds for First-Trimester Viability

Non-Viable Pregnancy Prediction

• Progesterone <6.3 ng/mL has 73% sensitivity and 99% specificity for detecting non-viable pregnancy, with positive predictive values of 91-99% depending on prevalence 1
• At a cutoff of 10 ng/mL, sensitivity is 79% and specificity is 93% for distinguishing viable from non-viable pregnancies 2
• Progesterone <20 ng/mL demonstrates 95% sensitivity for non-viable pregnancy and 99% specificity for viable pregnancy 2

Viable Pregnancy Prediction

• Progesterone levels ≥20-25 ng/mL have 91% sensitivity and 75% specificity, with negative predictive values of 89-99% for ruling out non-viable pregnancy 1
• Mean progesterone in viable first-trimester pregnancies is approximately 46.5 ng/mL compared to 9.9 ng/mL in non-viable pregnancies 2
• A cutoff of 32.7 ng/mL provides 90% sensitivity with 75% negative predictive value and 92% specificity with 97% positive predictive value 3

Clinical Context Matters

When hCG is <2000 mIU/mL

• Progesterone measurement is most useful when hCG levels are below 2000 mIU/mL, as ultrasound becomes the preferred diagnostic tool above this threshold 4
• A progesterone level of 12 ng/mL provides optimal sensitivity with lowest false-positive rate in this specific context 4

Important Caveats

• A single progesterone level <5 ng/mL is suggestive but NOT diagnostic of non-viable pregnancy—rare cases of viable pregnancies with levels as low as 1.2 ng/mL have been documented 5
• Progesterone is produced by the corpus luteum until the luteal-placental shift at 6-10 weeks, so timing of measurement affects interpretation 5

Therapeutic Progesterone Dosing (Not Diagnostic Levels)

For Early Pregnancy Bleeding with Prior Miscarriage

• Vaginal micronized progesterone 400 mg twice daily is recommended as an alternative to 90-mg gel or 200-mg suppository daily 6

For Preterm Birth Prevention

• 17-alpha-hydroxyprogesterone caproate (17P) 250 mg IM weekly from 16-20 weeks until 36 weeks for singleton pregnancies with prior spontaneous preterm birth 6, 7
• Vaginal progesterone 90-mg gel or 200-mg suppository daily until 36 weeks for singleton pregnancies with short cervical length (≤20 mm) at ≤24 weeks 7
• Vaginal progesterone 400 mg daily after successful tocolysis increases latency and reduces respiratory distress syndrome 7

Where Progesterone Does NOT Work

• No benefit in multiple gestations (twins, triplets) for preterm birth prevention 8, 7
• Insufficient evidence for active preterm labor, tocolysis, or preterm premature rupture of membranes 8, 7