Table 1.

Values for calculation of percentiles (5^th, 25^th, 50^th, 75^th and 95^th) for fetal brainstem substructural and cerebellar measurements, according to the linear equation: size (in mm or mm²) = (gestational age in weeks × k) + d

	5th percentile		25th percentile		50th percentile		75th percentile		95th percentile
Fetal brain measurement	k	d	k	d	k	d	k	d	k	d
Midbrain
Area (in mm2)	2.81	–14.26	3.11	–15.78	3.35	–16.99	3.62	–18.38	4.10	–20.81
RC diameter (in mm)	0.19	2.59	0.21	2.80	0.22	2.96	0.23	3.14	0.25	3.42
AP diameter (in mm)	0.31	1.96	0.34	2.11	0.35	2.21	0.37	2.32	0.40	2.47
Total pons
Area (in mm2)	5.05	–62.26	5.79	–71.34	6.28	–77.35	6.79	–83.71	7.70	–94.82
RC diameter (in mm)	0.39	–1.97	0.44	–2.22	0.48	–2.38	0.51	–2.55	0.55	–2.78
AP diameter (in mm)	0.33	–0.59	0.36	–0.64	0.38	–0.68	0.40	–0.72	0.44	–0.78
Basis pontis
Area (in mm2)	1.79	–23.89	2.14	–28.50	2.43	–32.42	2.81	–37.43	3.64	–48.51
AP diameter (in mm)	0.14	–0.91	0.17	–1.09	0.19	–1.22	0.21	–1.36	0.25	–1.57
Pontine tegmentum
Area (in mm2)	2.88	–33.02	3.37	–38.64	3.72	–42.59	4.07	–46.58	4.58	–52.39
AP diameter (in mm)	0.14	0.70	0.16	0.80	0.17	0.87	0.19	0.94	0.21	1.05
Medulla oblongata
Area (in mm2)	2.60	–22.60	3.01	–26.13	3.27	–28.44	3.55	–30.84	4.01	–34.83
RC diameter (in mm)	0.23	2.33	0.25	2.59	0.27	2.76	0.29	2.92	0.31	3.15
AP diameter (in mm)	0.19	0.34	0.21	0.38	0.23	0.41	0.25	0.45	0.28	0.49
Cerebellar vermis
RC diameter (in mm)	0.72	–6.83	0.79	–7.48	0.84	–7.90	0.88	–8.32	0.95	–8.93
AP diameter (in mm)	0.53	–5.26	0.57	–5.69	0.60	–6.02	0.64	–6.38	0.70	–6.99
Transcerebellar diameter (in mm)	1.52	–12.48	1.60	–13.13	1.66	–13.60	1.72	–14.15	1.85	–15.23

AP, anteroposterior; RC, rostrocaudal.