1. Impact of potential sources of heterogeneity on the sensitivity of a first‐trimester scan in detecting fetal structural anomalies.

Impact of potential sources of heterogeneity on the sensitivity of a first‐trimester scan in detecting fetal structural anomalies
Covariate	First‐trimester scan
	Sensitivity estimate (95% CI)		P value
	Fetuses affected	Anomalies	Fetuses affected	Anomalies
1. Study period*
1999	31.6 (19.2 to 44.0)	29.5 (18.1 to 40.9)	‐	‐
2009	37.6 (30.8 to 44.3)	38.7 (32.2 to 45.2)	‐	‐
2019	44.0 (29.1 to 58.9)	48.7 (35.7 to 61.8)	‐	‐
Beta	0.3 (‐0.03 to 0.08)	0.04 (‐0.01 to 0.09)	0.311	0.08
2. Reported prevalence of isolated ventricular septal defects
≤ 1.7 per 1000	41.0 (32.8 to 48.1)	41.3 (32.6 to 50.0)	0.195	0.429
< 1.7 per 1000	31.9 (22.3 to 41.6)	35.7 (25.2 to 46.2)
3. Anatomical screening protocol
Basic	39.4 (36.2 to 27.5)	39.7 (27.8 to 51.6)	0.915 (basic vs detailed) 0.810 (basic vs not reported)	0.845 (basic vs detailed) 0.896 (basic vs not reported)
Detailed	36.2 (27.5 to 58.3)	38.2 (28.7 to 47.7)
Not reported	36.4 (27.5 to 45.0)	41.1 (23.7 to 58.5)
4. Cardiac screening protocol
Basic	39.5 (30.5 to 48.5)	39.1 (29.0 to 49.2)	0.915 (basic vs extended) 0.277 (basic vs not reported)	0.567 (basic vs extended) 0.591 (basic vs not reported)
Extended	38.7 (26.7 to 50.7)	44.0 (30.5 to 57.4)
Not reported	30.9 18.7 to 43.1)	34.7 (22.5 to 46.8)
5. Country
LIC	67.7 (49.7 to 85.8)	67.9 (48.5 to 87.3)	0.002**	0.006**
HIC	34.4 (29.2 to 39.6)	36.5 (30.5 to 42.5)
CI: confidence interval; LIC: low‐ or lower‐middle‐income country; HIC: high‐ or upper‐middle‐income country
*Study period was defined by the year in which the study period ended. The impact of the study period on the estimated sensitivity was investigated as a continuous variable through meta‐regression. **P < 0.05 was considered statistically significant.