Reference ranges for foetal nasal bone length, prenasal thickness, and interocular distance at 18 to 24 weeks’ gestation in low-risk pregnancies

Table 1 Results of NBL, PNT and IOD According to Gestational Weeks

Gestational Weeks	NBL		PNT		IOD
Gestational Weeks	n	Mean	n	Mean	n	Mean
18	51	5.53	51	3.52	54	11.15
19	54	5.83	54	3.63	58	11.55
20	47	6.53	47	4.03	53	12.30
21	60	6.79	60	4.38	68	12.79
22	55	7.29	55	4.63	57	13.49
23	55	7.63	55	4.48	60	13.64
24	55	8.33	55	5.06	56	14.54

ISSN: 1471-2393