What beta‑human chorionic gonadotropin (β‑hCG) level 72 hours before a level of 230 mIU/mL would indicate a viable pregnancy?

β‑hCG Level 72 Hours Prior Indicating Viable Pregnancy

For a current β‑hCG of 230 mIU/mL to indicate a viable pregnancy, the level 72 hours earlier should have been approximately 115–150 mIU/mL, representing a minimum 53% rise over 48 hours or a 120% rise over 72 hours. 1, 2

Evidence-Based β‑hCG Kinetics in Viable Pregnancy

Minimum Rise Requirements

• The slowest acceptable rise for a viable intrauterine pregnancy is 53% over 48 hours, based on a prospective study of 287 symptomatic women with confirmed viable pregnancies 1
• Over 72 hours, viable pregnancies require a minimum 120% increase in β‑hCG to remain within normal parameters 2
• Working backward from 230 mIU/mL: a 53% rise over 48 hours means the prior level was ~150 mIU/mL; a 120% rise over 72 hours means the prior level was ~105 mIU/mL 1, 2

Typical vs. Minimum Rise Patterns

• The median rise in viable pregnancy is 50% per day (1.5-fold daily), translating to 124% over 48 hours and approximately 238% over 72 hours 1
• For a current level of 230 mIU/mL with typical kinetics, the 72-hour prior value would be ~68 mIU/mL (230 ÷ 3.38) 1
• However, using the minimum viable threshold is clinically safer: a 72-hour prior level of 105–150 mIU/mL defines the lower boundary of normal 1, 2

Clinical Application Algorithm

Step 1: Calculate the Expected Prior Level

• If the 72-hour prior β‑hCG was ≥105 mIU/mL, the current 230 mIU/mL represents at least a 120% rise and is consistent with viable pregnancy 2
• If the 72-hour prior β‑hCG was 150–190 mIU/mL, the rise is in the lower-normal range (21–53% over 48 hours) but still compatible with viability 1
• If the 72-hour prior β‑hCG was >190 mIU/mL, the rise is <21% and suggests nonviable or ectopic pregnancy 1

Step 2: Integrate with Ultrasound Timing

• At β‑hCG 230 mIU/mL, transvaginal ultrasound has only 33% sensitivity for detecting intrauterine pregnancy and should be deferred 3
• Repeat β‑hCG in exactly 48 hours to confirm continued appropriate rise (minimum 53% increase to ≥352 mIU/mL) 3, 1
• Schedule ultrasound when β‑hCG reaches 1,000–3,000 mIU/mL, the validated discriminatory threshold for gestational sac visualization 3, 4

Step 3: Serial Monitoring Protocol

• Obtain baseline β‑hCG immediately, then repeat at 48-hour intervals until the level permits definitive ultrasound diagnosis 3
• An increase ≥53% over 48 hours confirms viable pregnancy kinetics; plateau (<15% change) or suboptimal rise (10–53%) mandates gynecology consultation for possible ectopic pregnancy 3, 1
• Continue monitoring until β‑hCG reaches the discriminatory threshold (1,000–3,000 mIU/mL), at which point ultrasound can reliably confirm intrauterine location 3, 4

Critical Pitfalls to Avoid

• Do not rely on a single β‑hCG value to diagnose viability or exclude ectopic pregnancy (Level B recommendation); serial measurements are mandatory 3
• Do not use the traditional 3,000 mIU/mL discriminatory threshold to exclude ectopic pregnancy, as it has no diagnostic utility (positive likelihood ratio 0.8) 3
• Do not defer ultrasound in symptomatic patients based on "low" β‑hCG, as 22% of ectopic pregnancies present with levels <1,000 mIU/mL 3
• Avoid premature diagnosis of nonviable pregnancy based on slower-than-median rise; the minimum 53% increase over 48 hours defines the lower boundary of normal, not the median 1

Special Considerations

• In assisted reproductive technology pregnancies, a single β‑hCG >100 mIU/mL at 14 days post-transfer has 83% positive predictive value for viability 5
• For patients with risk factors for ectopic pregnancy (prior ectopic, pelvic inflammatory disease, IUD), maintain heightened vigilance even with appropriate β‑hCG kinetics 3
• If the patient develops severe pain, heavy bleeding, or hemodynamic instability, perform immediate ultrasound regardless of β‑hCG level 3