What are normal progesterone levels in early pregnancy?

Normal Progesterone Levels in Early Pregnancy

In early pregnancy, serum progesterone levels typically range from 10-48 ng/mL (approximately 32-153 nmol/L) between 5-10 weeks gestation, with mean values around 22 ng/mL (70 nmol/L). 1

Diagnostic Thresholds for Pregnancy Viability

Levels Indicating Non-Viable Pregnancy

• Progesterone <6.3 ng/mL (<20 nmol/L) has 73% sensitivity and 99% specificity for detecting non-viable pregnancy, with over 90% of patients at this level ultimately diagnosed with pregnancy loss 2
• Progesterone <10 ng/mL (<32 nmol/L) indicates subnormal corpus luteum function and is associated with increased risk of early pregnancy complications 1
• A threshold of <45 nmol/L (approximately 14 ng/mL) differentiates viable from non-viable pregnancies with 88% sensitivity and 88% specificity 3

Levels Indicating Viable Pregnancy

• Progesterone ≥20-25 ng/mL (63.6-79.5 nmol/L) predicts viable pregnancy in over 90% of cases, with 91% sensitivity and 75% specificity 2
• In threatened abortion cases, progesterone <90.62 nmol/L (approximately 28.5 ng/mL) represents a critical threshold, below which each 1 nmol/L decrease increases miscarriage risk by 3% 4

Important Clinical Caveats

The Luteal-Placental Shift

• Progesterone production transitions from the corpus luteum to the placenta at 6-10 weeks gestation 5, 6
• During this transition period, progesterone levels may temporarily fluctuate, making single measurements less reliable 5

Limitations of Single Measurements

• No absolute cutoff exists - rare cases of viable pregnancies have been documented with progesterone as low as 1.2 ng/mL, though these are exceptional 6
• Serial measurements combined with β-hCG trends and ultrasound provide superior diagnostic accuracy compared to isolated progesterone values 5
• A single progesterone <5 ng/mL is suggestive but not diagnostic of non-viability; routine intervention based solely on this threshold risks interrupting desired viable pregnancies 6

Clinical Application Algorithm

For symptomatic patients (bleeding/pain):

• Progesterone <6.3 ng/mL: High likelihood (>90%) of non-viable pregnancy 2
• Progesterone 6.3-20 ng/mL: Indeterminate zone requiring serial monitoring with β-hCG and ultrasound 2, 3
• Progesterone >20-25 ng/mL: High likelihood (>90%) of viable pregnancy 2

For asymptomatic patients:

• Normal range: 10-48 ng/mL between 5-10 weeks 1
• Values persistently <10 ng/mL warrant closer surveillance even without symptoms 1