Parental Age Classification
1 = Less than 30 years old
2 = More than 30 years old

Parental Gender
1 = Male
2 = Female

Parental Race
1 = Malay
2 = Chinese
3 = Indian
4 = Others

Parental Race (Malay vs. non-Malay)
0 = Non Malay
1 = Malay

Parental Education Level
1 = Primary Education
2 = Secondary Education
3 = Tertiary Education

Family Income Classification
0 = M40T20
1 = B40

Stay Outside KL
1 = Inside KL
2 = Outside KL

Children Age Group
1 = 4 years old or less
2 = More than 4 years old

Children Gender
1 = Male
2 = Female
9 = Missing

Children Gender
0 = Female
1 = Male

History of ASD among Siblings
0 = No
1 = Yes

Hospital of Birth
1 = Government
2 = Private

State of Birth
1 = Kuala Lumpur
2 = Selangor
3 = Others

Prematurity
0 = No Prem
1 = Prem

Status of Immunisation
1 = Up-to-date
2 = Missed
9 = Missing

Stage of ASD
1 = Mild Autism
2 = Moderate Autism
3 = No Autism

Speak at Three Years Old
1 = Yes
2 = No
9 = Missing

Advanced Maternal Age
1 = 35 years old or less
2 = More than 35 years old

Mode of Delivery
1 = Spontaneous Vertex Delivery
2 = Assisted Delivery
3 = Caesarean Section

Hemoglobin Level
1 = 11.0 g/dL or less
2 = More than 11.0 g/dL

Type of House
1 = Bunglow
2 = Semi-Detached
3 = Terrace
4 = Town House
5 = Condominium
6 = Apartment
7 = Flat
9 = Missing

Classification of House's Age
1 = 25 years or less
2 = More than 25 years

Parental Smoking Status
0 = Non-Smoker
1 = Ex-Smoker
2 = Active Smoker

0 = no risk
1 = yes risk

Exposure to the Soil
1 = Everyday
2 = Once a Week
3 = Once a Month
4 = Never
9 = Missing

Sucking Own Hand
1 = All the Time
2 = Just Before Sleep
3 = Never
9 = Missing

PICA (Eat Things Other than Food)
1 = Yes
2 = No
3 = Not Sure
9 = Missing

Washing Children Hand
1 = Every Time After Hand Contact
2 = Before Eating and While Taking Bath
3 = While Taking Bath
9 = Missing

Drinking the Milk
1 = More than 2 Times Per Day
2 = 1 to 2 Times Per Day
3 = Never
9 = Missing

Eating Fruits and Vegetables
1 = Every Meal
2 = Once a Day
3 = Once a Week
4 = Never
9 = Missing

Autism Status
0 = TD Children
1 = ASD Children

Autism Status
1 = ASD Children
2 = TD Children

birth order category
0 = subsequent child
1 = first child

birth weight category
0 = more than 4.0kg
1 = 2.5kg to 4.0kg
2 = less than 2.5kg

Pb Level (µg/dL) (Binned)
1 = <= .17
2 = .18 - .26
3 = .27 - .49
4 = .50+

Cd Level (mcg/dL) (Binned)
1 = <= .03
2 = .04 - .07
3 = .08 - .12
4 = .13+

0 = T20
1 = M40
2 = B40

0 = <0.00, low
1 = 0.00 to 1.00 , normal
2 = >1.0,high