Background Sacrococcygeal Teratoma (SCT) is a rare tumour that is ‘benign’ but carries with it a variable prognosis for survival.

Methods Suspected and confirmed cases presenting before 1 year of age were selected using a regional, population-based, multiple-source, anomaly register from a birth cohort of 1,215,140. Suspected cases were analysed separately as false positive ultrasound diagnoses.

Results 35 confirmed cases of SCT delivered between 1995–2012. Total and live births prevalences were 0.29 per 10,000 births (95% CI 0.19–0.38) and 0.21 per 10,000 live births (95% CI 0.13–0.29). Sex ratio (M:F) was 1:2.4.

22 cases were diagnosed prenatally (median gestation 20⁺¹ weeks), the sensitivity of antenatal ultrasound was 62.3% (95% CI 46.8–78.9). The uptake of termination following prenatal diagnosis was 31.2%. There were 6 antenatal false positives; therefore the positive predictive value of antenatal ultrasound was 78.6% (95% CI 63.4–93.8). The confirmed anomalies for the false positives cases were spinal and neural tube defects. Histopathology was ascertained in 27 cases at surgery/postmortem, the tumours were benign (52%), immature (37%), and mixed (11%). Altman staging (final confirmed) was recorded in 25 cases; the majority of cases were stage II (56.0%). A comparison of prenatal ultrasound and MRI was made. The survival to 1 year of age amongst liveborn cases (n = 25) was 84.0% (95% CI 69.6–98.4), and amongst all cases with spontaneous outcomes (excludes terminations) was 75.0% (95% CI 59.0–91.0).

Conclusion This population-based series indicates that prenatal ultrasound is relatively sensitive and specific in diagnosing SCT.

The survival rate in liveborn cases is good.