Table 2.
Percent agreement of birth certificate-derived prepregnancy body mass index categories with medical record derived categories in the validation study subcohort by race/ethnicity and gestational age at delivery. a,b
| Birth certificate classification | Birth certificates n (%) | Validation study n | Medical record classification | |||
|---|---|---|---|---|---|---|
| Underweight | Normal weight and overweight | Obese class 1 | Obese classes 2 & 3 | |||
| Non-Hispanic white women delivering at term | ||||||
| Underweight | 27,474 (3.2) | 90 | 74.4% | 25.6% | 0% | 0% |
| Normal weight or overweight | 511,213 (64.6) | 90 | 0% | 98.9% | 1.1% | 0% |
| Obese class 1 | 74,008 (8.7) | 84 | 0% | 13.1% | 79.8% | 7.1% |
| Obese classes 2&3 | 58,227 (6.8) | 90 | 0% | 2.2% | 6.7% | 91.1% |
| Non-Hispanic black women delivering at term | ||||||
| Underweight | 3,928 (0.5) | 84 | 69.0% | 31.0% | 0% | 0% |
| Normal weight or overweight | 78,007 (9.1) | 90 | 2.2% | 93.3% | 2.2% | 2.2% |
| Obese class 1 | 17,631 (2.1) | 87 | 0% | 31.0% | 51.7% | 17.2% |
| Obese classes 2&3 | 15,540 (1.8) | 90 | 0% | 3.3% | 5.6% | 91.1% |
| Non-Hispanic white women delivering preterm | ||||||
| Underweight | 3,201 (0.4) | 65 | 69.2% | 30.8% | 0% | 0% |
| Normal weight or overweight | 37,541 (4.4) | 90 | 0% | 98.9% | 1.1% | 0% |
| Obese class 1 | 6,118 (0.7) | 69 | 0% | 10.1% | 72.5% | 17.4% |
| Obese classes 2&3 | 5,251 (0.6) | 67 | 0% | 1.4% | 9.0% | 89.6% |
| Non-Hispanic black women delivering preterm | ||||||
| Underweight | 686 (0.8) | 19 | 57.9% | 42.1% | 0% | 0% |
| Normal weight or overweight | 10,361 (1.2) | 63 | 0% | 93.3% | 6.7% | 0% |
| Obese class 1 | 2,304 (0.3) | 51 | 0% | 13.7% | 68.6% | 17.7% |
| Obese classes 2&3 | 2,069 (0.2) | 48 | 0% | 0% | 0% | 100% |
Agreement proportion is calculated as the probability that women in each birth certificate-derived prepregnancy BMI category were truly underweight, truly normal weight, truly overweight, truly obese class 1, and truly obese classes 2 and 3 by the medical record.
Preterm birth is defined as <37 weeks gestation based on birth certificate-derived gestational age; prepregnancy body mass index categories were underweight, <18.5 kg/m2; normal or overweight, 18.5–29.9 kg/m2; obese class 1, 30–34.9 kg/m2; obese classes 2 and 3, ≥35 kg/m2.