Table 1.
Main characteristics at birth of mothers and children included in the ELFE cohort and comparison with the national references (birth certificates or 2010 National Perinatal Surveya)
| n b | ELFE crude | ELFE weighted | National referencec | ||
|---|---|---|---|---|---|
| Parents | % (n) or mean (SD) | % or mean ± SE | % or mean | ||
| Mother’s age at deliveryd | <25 years | 17 780 | 12.1 (2150) | 14.1 ± 0.0 | 13.9 |
| 25–34 years | 66.4 (11 808) | 64.5 ± 0.0 | 64.5 | ||
| ≥35 years | 21.5 (3820) | 21.4 ± 0.0 | 21.6 | ||
| Maternal educationd | University degree | 17 779 | 60.1 (10 689) | 52.4 ± 0.0 | 52.3 |
| Maternal employment | Employed | 17 354 | 79, 9 (13 864) | 65.9 ± 0.5 | |
| Housewife | 9, 6 (1663) | 15.9 ± 0.5 | |||
| Unemployed | 5, 8 (1016) | 6.4 ± 0.3 | |||
| Other | 4.7 (811) | 6.6 ± 0.4 | |||
| Paternal employment | Employed | 17 273 | 91.6 (15 824) | 84.1 ± 0.3 | 87.4 |
| Mother born out of Franced | 17 642 | 13.2 (2322) | 18.4 ± 0.0 | 18.7 | |
| Familial status | Lone mother | 17 684 | 5.5 (976) | 7.6 ± 0.3 | |
| Parityd | Primiparous | 17 693 | 45.6 (8068) | 43.3 ± 0.0 | 43.1 |
| Maternal smoking | Never smoker | 17 640 | 79.9 (14 085) | 78.3 ± 0.4 | |
| BMI category before pregnancy | Underweight | 17 546 | 7.9 (1380) | 7.9 ± 0.3 | 8.2 |
| Overweight | 17.5 (3077) | 18.4 ± 0.4 | 17.3 | ||
| Obese | 10.0 (1752) | 11 ± 0.3 | 9.9 | ||
| Gestational diabetes | 16 959 | 7.5 (1271) | 7.6 ± 0.3 | 7.1 | |
| Gestational hypertension | 17 342 | 3.4 (586) | 3.8 ± 0.2 | 4.6 | |
| Caesarean section | 17 375 | 18.1 (3158) | 18.6 ± 0.9 | ||
| Infants | |||||
| Inclusion period (2011) | 1–4 April | 18 143 | 15.2 (2765) | 23.9 | |
| 27–28 June, 1–4 July | 25.2 (4575) | 26.5 | |||
| 27–29 September, 1–4 October | 28.3 (5128) | 25.8 | |||
| 28–30 November, 1–5 December | 31.2 (5675) | 24.8 | |||
| Offspring gender | Male | 17 967 | 51.4 (9 233) | 51.4 ± 0.4 | |
| Twins | 17 858 | 1.6 (284) | 1.6 ± 0.1 | 2.7 | |
| Birthweight | Grams | 17 739 | 3309 (499) | 3305 ± 5 | |
| Preterm birth (weeks of amenorrhoea) | 33–36 | 17 858 | 6.5 (1156) | 5.9 ± 0.2 | |
SD, standard deviation; SE, standard error; BMI, body mass index.
b
Mothers or infants with available data at time of analysis (some included subjects have asked for withdrawal of their data).
c
National reference when available, restricted to a population with the same eligibility criteria for the National Perinatal Survey but not for the birth certificates.
d
Variables used for marginal calibration of weighted variables (in addition to region of residence).