Table 1.
Descriptive characteristics of the analytic sample of 1,109 women delivering twin pregnancies at Magee-Womens Hospital, Pittsburgh PA, 1998–2013.
| Characteristic | Median [Interquartile range] or n(%) |
|---|---|
| Maternal age (years) a | |
| <20 | 34 (3.1) |
| 20–29 | 391 (31.5) |
| ≥30 | 680 (61.4) |
| Parity | |
| 0 | 482 (43.5) |
| 1 | 523 (47.2) |
| 2+ | 104 (9.4) |
| Pre-pregnancy Body Mass Index (kg/m2) | |
| Normal weight (18.5–24.9) | 573 (50.0) |
| Overweight (25–29.9) | 287 (24.0) |
| Obese (≥30) | 249 (21.8) |
| Maternal height (cm) | 165 [160, 170] |
| Smoked during pregnancy | 111 (10.0) |
| Race | |
| Non-Hispanic White | 891 (80.3) |
| Non-Hispanic Black | 168 (15.2) |
| Hispanic | 11 (1.0) |
| Non-Hispanic Other | 39 (3.5) |
| Insurance status | |
| Private | 683 (61.6) |
| Medicaid | 405 (36.5) |
| Other | 21 (1.9) |
| Use of Assisted Reproductive Technology | |
| IVF | 232 (21.9) |
| Other or unspecified ART (includes Clomid, Gonadotropin, and/or intrauterine insemination) | 120 (10.8) |
| None | 757 (68.3) |
| Gestational age at first ultrasound | 12 [8, 18] |
| Gestational age at delivery | 37 [36, 38] |
| Prenatal weight measurements, number | 11 [10, 13] |
a
Maternal age missing in 4 women