Long-term significant seasonal differences in the numbers of new-borns with an orofacial cleft in the Czech Republic – a retrospective study

Table 1 Boys born during 1964–2000

Month		I	II	III	IV	V	VI	VII	VIII	IX	X	XI	XII
NC	Σ	221,358	208,245	244,215	241,422	220,682	229,161	230,717	217,741	213,307	203,066	193,035	199,661
	N	37	37	37	37	37	37	37	37	37	37	37	37
	x̄	5982.65	5628,24	6600.41	6524.92	5964.38	6193.54	6235.59	5884.89	5765.05	5488.27	5217.16	5396.24
	SE	198.91	201.76	245.50	241.65	374.36	209.70	203.04	185.84	192.77	188.69	178.70	195.72
CL	Σ	74	77	72	67	71	72	64	88	69	68	54	56
	N	37	37	37	37	37	37	37	37	37	37	37	37
	x̄	2.00	2.08	1.95	1.81	1.92	1.95	1.73	2.38	1.86	1.84	1.46	1.51
	SE	0.22	0.25	0.25	0.21	0.24	0.22	0.23	0.30	0.23	0.23	0.20	0.20
CLP	Σ	108	129	132	133	155	142	133	138	102	98	109	118
	N	37	37	37	37	37	37	37	37	37	37	37	37
	x̄	2.92	3.49	3.57	3.59	4.19	3.84	3.59	3.73	2.76	2.65	2.95	3.19
	SE	0.28	0.38	0.30	0.32	0.38	0.36	0.30	0.36	0.26	0.34	0.31	0.33
CP	Σ	75	70	78	60	98	70	85	72	71	77	61	64
	N	37	37	37	37	37	37	37	37	37	37	37	37
	x̄	2.03	1.89	2.11	1.62	2.65	1.89	2.30	1.95	1.92	2.08	1.65	1.73
	SE	0.27	0.26	0.22	0.22	0.32	0.25	0.20	0.22	0.25	0.26	0.23	0.21

Groups of boys: NC non-cleft control, CL cleft lip, CLP cleft lip and palate, CP cleft palate
Σ - total monthly number corresponding to all boys that born in a given month for 37 years; N – number of years; x̄ – mean monthly number of newborn boys;
SE – standard error of the mean

ISSN: 1471-2393