Table1.
Demographics of pregnant women stratified by fetal sex. (n = 902,513).
| Variables | Fetal sex | Mean difference mean (95% CI) | p-valuea | |
|---|---|---|---|---|
| Male (%) (n = 464,075) | Female (%) (n = 438,438) | |||
| Continuous variables [Mean (n)] | ||||
| Maternal age (years) | 32.0 (5.3) | 32.1 (5.4) | 0.00 (− 0.03 to 0.02) | 0.165 |
| Pre-pregnant body mass index (kg/m2) | 21.24 (3.47) | 21.22 (3.47) | 0.02 (0.01 to 0.04) | 0.005 |
| Maternal height (cm) | 158.3 (5.5) | 158.3 (5.5) | − 0.01 (− 0.03 to 0.01) | 0.394 |
| Categorical variables [n (%)] | ||||
| Year | 0.273 | |||
| 2007–2009 | 76,087 (51.6) | 71,337 (48.4) | ||
| 2010–2012 | 136,261 (51.4) | 128,856 (48.6) | ||
| 2013–2015 | 251,727 (51.4) | 238,245 (48.6) | ||
| Parity | 0.066 | |||
| Primiparous | 240,523 (51.5) | 226,388 (48.5) | ||
| Multiparous | 223,552 (51.3) | 212,050 (48.7) | ||
| Conception method | 0.928 | |||
| Without ART | 445,831 (51.4) | 421,218 (48.6) | ||
| With ART | 182,44 (51.4) | 17,220 (48.6) | ||
| Maternal smoking during pregnancy | 0.488 | |||
| Yes | 21,223 (51.7) | 19,833 (48.3) | ||
| No | 353,727 (51.4) | 334,502 (48.6) | ||
| Missing | 89,125 (51.5) | 84,103 (48.6) | ||
All mean differences are calculated using females as the reference.
CI confidence interval, BMI body mass index, ART assisted reproductive technology.
aStudent's t-test was used for continuous variables and the chi-squared test for categorical variables.