Table 1.
Baseline demographics of study participants (n= 17,027) by categories of baseline BMI in 1989.
| Prepregnancy BMI Category (Range, kg/m2) | |||||
|---|---|---|---|---|---|
|
| |||||
| Underweight (< 18.5) | Normal (18.5–24.9) | Overweight (25–29.9) | Obese (≥ 30) | ||
| Number of Women* | 807 | 12,775 | 2388 | 1008 | p-value |
| Maternal Age, n(%) | <0.001 | ||||
| <30 yrs | 425 (52.7) | 5890 (46.1) | 973 (40.8) | 389 (38.6) | |
| 30–34 yrs | 311 (38.5) | 5246 (41.1) | 1048 (43.9) | 443 (44.0) | |
| 35–39 yrs | 66 (8.2) | 1510 (11.8) | 332 (13.9) | 159 (15.8) | |
| 40–44 yrs | 5 (0.6) | 129 (1.0) | 35 (1.5) | 17 (1.7) | |
| Pre-pregnancy Smoking, n(%) | <0.001 | ||||
| Never | 616 (76.3) | 9063 (70.9) | 1643 (68.8) | 675 (67.0) | |
| Former | 103 (12.8) | 2486 (19.5) | 466 (19.5) | 201 (19.9) | |
| Current | 87 (10.8) | 1206 (9.4) | 276 (11.6) | 129 (12.8) | |
| Physical Activity, MET-hrs/week† | 17.4 [7.3–41.1] | 17.7 [7.2–37.6] | 12.9 [5.2–29.1] | 9.9 [3.7–25.7] | <0.001 |
| Multivitamin Use, n(%) | 359 (44.5) | 6194 (48.5) | 1153 (48.3) | 513 (50.9) | 0.25 |
| Ever OC Use | <0.001 | ||||
| Never | 157 (19.5) | 2243 (17.6) | 429 (18.0) | 184 (18.3) | |
| Past | 452 (56.0) | 7064 (55.3) | 1398 (58.5) | 632 (62.7) | |
| Current | 197 (24.4) | 3453 (27.0) | 556 (23.3) | 192 (19.1) | |
| History of Infertility, n(%) | 88 (10.9) | 1538 (12.0) | 342 (14.3) | 173 (17.2) | <0.001 |
| History of Infertility Drug Use‡, n(%) | 95 (11.8) | 1365 (10.7) | 263 (11.0) | 150 (14.9) | 0.002 |
| Married, n(%) | 592 (73.4) | 9555 (74.8) | 1845 (77.3) | 761 (75.5) | 0.05 |
| Caucasian, n(%) | 739 (91.6) | 11886 (93.0) | 2217 (92.8) | 947 (94.0) | 0.26 |
| Parity, n(%) | <0.001 | ||||
| Nulliparous | 448 (55.5) | 6461 (50.6) | 1028 (43.1) | 430 (42.7) | |
| 1 | 201 (24.9) | 3476 (27.2) | 741 (31.0) | 348 (34.5) | |
| 2 | 130 (16.1) | 2163 (16.9) | 440 (18.4) | 162 (16.1) | |
| 3+ | 28 (3.5) | 673 (5.3) | 179 (7.5) | 68 (6.7) | |
| History of Long Menstrual Cycles, n(%) | 35 (4.3) | 494 (3.9) | 117 (4.9) | 71 (7.0) | <0.001 |
Abbreviations: BMI, body mass index; MET, metabolic equivalent task; OC, oral contraceptive. Differences across categories were tested using a chi-squared test for categorical variables and Kruskal-Wallis non-parametric tests for continuous variables.
*
49 eligible women were missing BMI in 1989. Sample sizes may vary due to missing data.
†
Data are median [25th percentile, 75th percentile].
‡
Question is from 1993 questionnaire (first time it was assessed).