Developmental Effects of Exposures to Environmental Factors: The Polish Mother and Child Cohort Study

Table 1

Child and parental characteristics.

Variables	n or mean	% or SD
Gender of the child (𝑁=406)
Boys	192	47.3
Girls	214	52.7
Birth weight (g); mean, SD (𝑁=388)	3352.5	488.3
Gestational age (weeks); mean; SD (𝑁=370)	39.3	1.4
Length (cm); mean, SD (𝑁=388)	54.9	2.9
Head circumference (cm); mean, SD (𝑁=384)	34.3	1.6
Chest circumference (cm); mean, SD (𝑁=382)	33.4	1.8
Breastfeeding (months) (𝑁=406)
No	66	16.3
<6	156	38.4
≥6	184	45.3
Nursery attendance at 12 months (𝑁=406)
Yes	27	6.7
No	379	93.3
Nursery attendance at 24 months (𝑁=193)
Yes	36	18.7
No	157	81.3
Age at Bayley test administration (months)
For one year old; mean, SD (𝑁=406)	12.4	1.3
For two years old; mean, SD (𝑁=198)	24.4	1.7
Number of siblings (𝑁=406)
0	234	57.6
≥1	172	42.4
Maternal age (years); mean, SD (𝑁=406)	29.8	4.4
Paternal age (years); mean, SD (𝑁=398)	31.8	5.5
Maternal education (𝑁=406)
Primary/vocational	33	8.1
Secondary	134	33.0
University	239	58.9
Paternal education (𝑁=401)
Primary/vocational	79	19.7
Secondary	161	40.1
University	161	40.1
Marital status (𝑁=406)
Married	311	76.6
Unmarried	95	23.4
Maternal employment (𝑁=406)
Employed	338	83.3
Unemployed	68	16.7
Socioeconomic status (𝑁=406)
High	71	17.5
Medium	292	71.9
Low	43	10.6
Maternal prepregnancy BMI (kg/m^2); mean, SD (𝑁=406)	22.3	3.6
Type of delivery (𝑁=366)
Cesarean	129	35.2
Vaginal	237	64.8
Alcohol consumption during pregnancy (𝑁=259)
Yes	22	8.5
No	237	91.5