TABLE 1.
Maternal characteristics of dichorionic twin pregnancies (n = 143), National Institute of Child Health and Human Development Fetal Growth Studies – Twins (2012–2013)
| Characteristic | n (%) |
| Race/ethnicity1 | |
| White/non-Hispanic | 81 (56.6) |
| Black/non-Hispanic | 31 (21.7) |
| Hispanic | 25 (17.5) |
| Asian | 6 (4.2) |
| Age, y | |
| 19–24 | 20 (14.0) |
| 25–29 | 28 (19.6) |
| 30–34 | 55 (38.5) |
| 35–39 | 27 (18.9) |
| 40–45 | 13 (9.1) |
| Prepregnancy BMI status, kg/m2 | |
| <18.5 | 7 (4.9) |
| 18.5–24.9 | 62 (43.4) |
| 25.0–29.9 | 33 (23.1) |
| ≥30.0 | 41 (28.7) |
| Height, cm | |
| <162 | 44 (30.8) |
| 162–167 | 50 (35.0) |
| ≥168 | 49 (34.3) |
| Smoking | |
| Nonsmoker | 123 (86.0) |
| Smoked before pregnancy only | 16 (11.2) |
| Smoked during pregnancy | 4 (2.8) |
| Nulliparous | 82 (57.3) |
| Education | |
| Less than high school | 9 (6.3) |
| High school diploma or GED2 or equivalent | 18 (12.6) |
| Some college or associate degree | 23 (16.1) |
| Bachelor’s degree | 60 (42.0) |
| Master’s degree or advanced degree | 33 (23.1) |
| Insurance | |
| Other | 35 (24.5) |
| Private or managed care | 108 (75.5) |
| Employed or full-time student | 113 (79.0) |
| Married or living with partner | 111 (77.6) |
| Any type of fertility intervention | 68 (47.6) |
| Pregestational diabetes | 2 (1.4) |
| Gestational diabetes | |
| Diet control | 9 (6.3) |
| Medication | 5 (3.5) |
| Unknown control | 1 (0.7) |
| Chronic hypertension | 10 (7.0) |
| Pregnancy hypertensive diseases | |
| Gestational hypertension | 9 (6.3) |
| Preeclampsia | 24 (16.8) |
| Unspecified hypertension | 7 (4.9) |
| Pregnancy outcome | |
| Live birth/live birth | 137 (95.8) |
| Live birth/fetal death | 3 (2.1) |
| Fetal death/fetal death | 3 (2.1) |
| Twin sex | |
| Male/male | 37 (25.9) |
| Female/female | 38 (26.6) |
| Male/female | 65 (45.5) |
| Unknown/unknown | 3 (2.1) |
| Zygosity (same-sex twins only) | |
| Monozygotic | 12 (16.0) |
| Dizygotic | 56 (74.7) |
| Missing | 7 (9.3) |
| Gestational age at delivery, wk | |
| 20–27 | 11 (7.7) |
| 28–34 | 33 (23.1) |
| ≥35 | 99 (69.2) |
| Birth weight discordance >20% | 16 (11.2) |
1
One woman self-identified as both non-Hispanic white and American Indian/Alaskan Native, and was grouped with the non-Hispanic white category.
2
GED, general equivalency diploma.