Failure of Interval Growth in germinal age

Definition

Failure of Interval Growth below 6 weeks refers to the absence of expected progressive increase in mean sac diameter (MSD) or yolk sac development during very early pregnancy, typically between 4–6 weeks of gestational age. It often indicates impaired embryonic development or early pregnancy failure when growth falls below the minimal expected rate on serial ultrasounds.

Images

Ultrasound Report - line

Example: "Gestational sac visualized within the uterine cavity measuring MSD __ mm, corresponding to approximately __ weeks. No yolk sac or embryo identified. Interval growth since prior scan minimal (less than1 mm/day). Findings suggestive of early pregnancy failure — advise correlation with β-hCG trend and follow-up transvaginal scan."

Conclusion

Sonographic features indicate inadequate interval growth for early gestation (<6 weeks). The mean sac diameter (MSD) shows subnormal increase (less than1 mm/day) and absence of yolk sac or embryo, suggesting possible anembryonic pregnancy or non-viable gestation.

Recommendation

• Repeat transvaginal scan in 7–10 days to assess for interval growth or yolk sac appearance.

• Obtain serial quantitative β-hCG (48–72 hours apart) — normally doubles approximately every 2 days in viable early pregnancy.

• Ensure proper dating by last menstrual period (LMP) to exclude late ovulation or implantation delay.

• Avoid premature diagnosis — repeat imaging is essential before confirming early pregnancy loss.

Differential diagnosis

• Very early intrauterine pregnancy (normal pre-embryonic stage).

• Ectopic pregnancy with pseudosac in uterine cavity.

• Anembryonic pregnancy (blighted ovum).

• Early intrauterine pregnancy with delayed ovulation.

Teaching points

• Mean sac diameter (MSD) should increase approximately 1 mm per day during early gestation.

• Yolk sac usually appears when MSD ≥ 8–10 mm; absence beyond this size raises suspicion for abnormal development.

• Embryo typically visualized when MSD ≥ 18 mm or gestational age ≥ 6 weeks on transvaginal scan.

• Always confirm findings with β-hCG trends and repeat scan before concluding early pregnancy failure.

References

1. Society of Radiologists in Ultrasound (SRU) guidelines for early pregnancy evaluation and viability criteria.

2. AIUM Practice Parameter for the Performance of Obstetric Ultrasound Examinations, 2023.

3. Aspectek Expectation Reference for Early Gestational Growth — CRL and MSD progression charts.

Discussion

Below 6 weeks, ultrasound findings can be subtle and highly dependent on imaging technique. Failure of interval growth should be interpreted cautiously, as delayed ovulation or implantation can mimic abnormal development. Serial scanning and biochemical correlation remain the gold standard for confirming early pregnancy viability. Overdiagnosis can be avoided by adhering to established SRU and AIUM cut-offs before labeling early pregnancy loss.

Gestational Sac growth chart — interval growth assessment

LMP

LMP not known

Scan date (current)

Prior scan date (for interval growth)

Enter prior scan date and prior MSD (below) to assess interval growth.

CGA (weeks / days) — optional (overrides LMP)

Enter CGA to override LMP-derived GA.

MSD (mm) — current

Prior MSD (mm) — optional

MSD vs GA

Mean sac diameter (MSD) plotted against gestational age (weeks)

Ready

Console (errors / logs):

Related cases

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Failure of Interval Growth — Germinal Age — Quiz

इंटरवल वृद्धि विफलता — जेर्माइनल आयु — क्विज़

10 MCQs — choose the best answer (A–D)

10 बहु-विकल्पीय प्रश्न — सर्वोत्तम उत्तर चुनें (A–D)

Created: Failure of Interval Growth (Germinal Age) — bilingual (EN/HI)