Assessing fetal growth impairments based on family data as a tool for identifying high-risk babies. An example with neonatal mortality

Table 2 Parameters of intercept (I) and slope (β) for predicting the birth weights of second-born children based on gestational age and sex * of first- and second-born children.

Gestational age of second child (g₁: weeks)	Gestational age of first child (g₂: weeks)
	28–33			34–35			36–37			38–39			40–41			>= 42			SD
	No.	I	β	No.	I	β	No.	I	β	No.	I	β	No.	I	β	No.	I	β
28–29	62	900	0.198	46	615	0.283	55	850	0.150	164	1030	0.066	190	735	0.148	37	840	0.111	240
30–31	117	980	0.348	65	740	0.385	114	1110	0.177	256	1050	0.168	309	880	0.207	42	195	0.359	320
32–33	167	1430	0.360	149	1270	0.312	293	920	0.407	557	1470	0.171	613	1230	0.224	78	1220	0.231	360
34	144	1650	0.407	196	1395	0.450	281	1075	0.462	563	1150	0.382	591	1140	0.352	83	1265	0.304	440
35	200	1675	0.496	261	1285	0.575	529	865	0.632	925	1095	0.481	941	1230	0.397	124	1255	0.379	440
36	301	2005	0.439	426	1140	0.722	1107	1110	0.649	2026	1335	0.490	1975	1365	0.439	244	1500	0.378	435
37	495	2450	0.341	712	1705	0.566	2420	1465	0.588	5388	1380	0.553	5147	1270	0.539	619	1385	0.485	435
38	659	2660	0.296	1132	2095	0.488	4263	1735	0.546	16229	1650	0.526	17312	1560	0.521	2329	1685	0.468	400
39	806	3050	0.212	1385	2355	0.448	5872	2030	0.501	31014	1750	0.541	43119	1690	0.534	5487	1790	0.490	385
40–41	1204	3295	0.171	1863	2785	0.344	8110	2345	0.446	51057	1855	0.553	132010	1780	0.554	25393	1905	0.510	390
>= 42	145	3520	0.125	182	3385	0.184	695	2670	0.382	4692	2220	0.488	19508	1855	0.568	8479	1960	0.531	415

No: Number of sibships included.
SD: Estimated Standard Deviation based on the regression model.
* The estimated sex correction (γ(s ₁, s ₂)) is:
-- 1.st female – 2.nd female: -65 grams
-- 1.st female – 2.nd male: +85 grams,
-- 1.st male – 2.nd female: -145 grams,
-- 1.st male – 2.nd male: 0 grams (reference).
Example
According to the model used, for a baby boy at 39 weeks of gestation with an older brother who weighed 2000 grams at 34–35 week of gestation, had a predicted birth weight of 3251 grams (Table 2, I(g ₁= 34–35, g ₂= 39) = 2355, β(g ₁= 34–35, g ₂= 39) = 0.448, γ(s ₁= male, s ₂= male) = 0, i.e., predicted birth weight = 2355 + 0.448 * 2000 grams + 0). Similarly, if the second-born was a girl, she would have a predicted birth weight of 3106 grams (Table 2, I(g ₁= 34–35, g ₂= 39) = 2355, β(g ₁= 34–35, g ₂= 39) = 0.448, γ(s ₁= male, s ₂= female) = -145 grams, i.e., predicted birth weight = 2355 + 0.448 * 2000 grams – 145 grams).

ISSN: 1471-2393