Table 1.
Description of study variables
| Variable name | Definition | Mean (Std Dev) or % |
|
|---|---|---|---|
| Infants without birth defects (N = 1716) | Infants with birth defects (N = 1695) | ||
| Low birth weight | Indicator (0,1) for low birth weight (<2500 grams) (%) | 11.0 | 24.5 |
| Birth weight | Birth weight in grams | 3164.1 (596.0) | 2931.1 (762.1) |
| Premature | Indicator (0,1) for gestational age <37 weeks (%) | 15.9 | 24.4 |
| Weeks | Pregnancy weeks elapsed prior to initiating prenatal care | 13.5 (8.1) | 13.7 (8.4) |
| Visits | Number of prenatal care visits | 7.2 (3.1) | 7.3 (3.2) |
| Inadequatea | Indicator (0,1) for inadequate prenatal care based on the Kessner Index (%) | 15.2 | 16.4 |
| Adequatea | Indicator (0,1) for adequate prenatal care based on the Kessner Index (%) | 27.1 | 26.5 |
| Multivitamin | Indicator (0,1) for multivitamin use during pregnancy (%) | 14.0 | 14.4 |
| Tetanus | Indicator (0,1) for tetanus immunization in 1st trimester (%) | 7.7 | 5.6 |
| Varicella | Indicator (0,1) for varicella immunization in 1st trimester (%) | 3.0 | 3.2 |
| Physical shocks | Indicator (0,1) for maternal exposure to physical shocks in 1st trimester (%) | 5.3 | 6.9 |
| Birth defect history | Indicator (0,1) for reporting any relatives to the child with the studied birth defects (%) | 6.1 | 22.7 |
| Difficulty in conception | Indicator (0,1) for reporting any difficulty in conception (%) | 12.2 | 12.2 |
| Acute maternal illness | Indicator (0,1) for any acute illnesses during pregnancy (%) | 47.8 | 50.7 |
| Chronic maternal illness | Indicator (0,1) for any chronic illnesses during pregnancy (%) | 17.2 | 19.7 |
| First trimester bleeding | Indicator (0,1) for vaginal bleeding in 1st trimester (%) | 8.1 | 8.7 |
| Live births | Number of previous live births | 1.3 (1.5) | 1.5 (1.7) |
| Miscarriages/stillbirths | Number of previous miscarriages and stillbirths | 0.3 (0.7) | 0.3 (0.7) |
| Maternal age (25–34 years)b | Indicator (0,1) for maternal age between 25 and 34 years inclusive (%) | 48.7 | 47.2 |
| Maternal age (≥35 years)b | Indicator (0,1) for maternal age of 35 years or older (%) | 14.3 | 21.7 |
| Maternal education–primaryc | Indicator (0,1) for completing primary school (%) | 14.9 | 15.5 |
| Maternal education–secondaryc | Indicator (0,1) for attending secondary school (%) | 31.4 | 30.7 |
| Maternal education–universityc | Indicator (0,1) for attending university (%) | 9.3 | 8.6 |
| Father's education–primaryc | Indicator (0,1) for completing primary school (%) | 19.5 | 18.3 |
| Father's education–secondaryc | Indicator (0,1) for attending secondary school (%) | 28.8 | 28.0 |
| Father's education–universityc | Indicator (0,1) for attending university (%) | 7.5 | 7.8 |
| Maternal employment | Indicator (0,1) for maternal employment status (%) | 43.2 | 44.6 |
| Father's employment | Indicator (0,1) for father's employment status (%) | 95.3 | 94.9 |
| Native ancestry | Indicator (0,1) for Native ancestry (%) | 52.9 | 53.6 |
| African ancestry | Indicator (0,1) for African ancestry (%) | 41.0 | 43.4 |
| European Latin ancestry | Indicator (0,1) for Latin European ancestry (%) | 58.2 | 59.6 |
| European non-Latin ancestry | Indicator (0,1) for non-Latin European ancestry (%) | 19.4 | 17.0 |
| Other ancestry | Indicator (0,1) for other ancestry (%) | 3.1 | 2.2 |
| Male | Indicator (0,1) for a male sampled subject (%) | 51.3 | 52.7 |
| Pregnancy year 95d | Indicator (0,1) for pregnancy in 1995 (%) | 8.9 | 9.0 |
| Pregnancy year 96d | Indicator (0,1) for pregnancy in 1996 (%) | 10.7 | 9.5 |
| Pregnancy year 97d | Indicator (0,1) for pregnancy in 1997 (%) | 9.5 | 10.1 |
| Pregnancy year 98d | Indicator (0,1) for pregnancy in 1998 (%) | 12.3 | 12.3 |
| Pregnancy year 99d | Indicator (0,1) for pregnancy in 1999 (%) | 14.3 | 15.5 |
| Pregnancy year 00d | Indicator (0,1) for pregnancy in 2000 (%) | 16.0 | 15.6 |
| Pregnancy year 01d | Indicator (0,1) for pregnancy in 2001 (%) | 18.4 | 18.5 |
| Pregnancy year 02d | Indicator (0,1) for pregnancy in 2002 (%) | 4.0 | 4.2 |
| Minas Geraise | Indicator (0,1) for a sampled birth in the state of Minas Gerais (%) | 14.9 | 15.8 |
| Paraibae | Indicator (0,1) for a sampled birth in the state of Paraiba (%) | 3.4 | 3.7 |
| Rio Grande do Sule | Indicator (0,1) for a sampled birth in the state of Rio Grande do Sul (%) | 25.9 | 26.0 |
| Santa Catarinae | Indicator (0,1) for a sampled birth in the state of Santa Catarina (%) | 21.4 | 21.2 |
Note: Standard Deviations are listed in parentheses.
aOmitted category is intermediate care.
bOmitted category is age ≤24 years.
cOmitted category is less than completed primary school (including not attending school).
dOmitted category is year 1994.
eOmitted category is the state of Sao Paulo.