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Table 1 Basic characteristics of the participants and the non-participants having live birth in the adjunct study of JECS

From: Determinants of polyunsaturated fatty acid concentrations in erythrocytes of pregnant Japanese women from a birth cohort study: study protocol and baseline findings of an adjunct study of the Japan environment & Children’s study

Variables All JECS Participants Participants of adjunct study Non-participants
n n n p
Mothers with live birth 8873   1823   7050   
Age at delivery (yrs) 8823 30.7 ± 5.1 1817 31.0 ± 5.3 7006 30.6 ± 5.0 0.0022
Marital status at registration (Married, %) 8798 94.7 1807 94.3 6991 94.8 0.39
Maternal education (<13 yrs, %) 8746 52.9 1790 54.1 6956 52.3 0.27
Paternal education (<13 yrs, %) 8695 59.3 1778 62.9 6917 59.6 0.013
Household income (million Japanese Yen) (%)
  < 2 575 7.4 121 7.4 454 7.4 0.15
 2 to <4 3111 39.9 694 42.6 2417 39.2  
 4 to <6 2290 29.4 454 27.8 1836 29.8  
 6 to <8 972 12.5 205 12.6 767 12.5  
  ≥ 8 842 10.8 157 9.6 685 11.1  
Living together with parents (Yes, %) 8835 46.7 1818 43.3 7017 47.5 0.0012
Smoking habits (%)
 Never smoked 4324 49.0 842 46.4 3482 49.6 0.034
 Ex-smokers who quit before pregnancy 2099 23.8 440 24.2 1659 23.6  
 Ex-smokers who quit after pregnancy 1752 19.8 377 20.8 1375 19.6  
 Smokers during early pregnancy 657 7.4 157 8.6 500 7.1  
Passive smoking (Yes, %) 8850 66.4 1819 69.2 7031 65.7 0.0047
Alcohol consumption (Drinkers, %) 8767 2.5 1791 1.7 6976 2.7 0.013
Prepregnancy BMI (kg/m2) 8872 21.8 ± 3.6 1823 21.9 ± 3.9 7049 21.7 ± 3.6 0.019
Body weight gain at delivery (kg) 8822 10.8 ± 4.2 1813 10.4 ± 4.2 7009 10.9 ± 4.1 <0.0001
Physical activity (mets · min/week) 8766 480 (0–18400) 1792 480 (0–18400) 6974 480 (0–16400) 0.81
Obstetrical/gynecological disease (%)
 Diabetes mellitus 8866 0.73 1822 0.49 7044 0.80 0.16
 Gestational diabetes mellitus 8866 1.5 1822 1.1 7044 1.6 0.11
 Pregnancy-induce hypertension 8866 1.1 1822 2.4 7044 0.82 <0.0001
 Hyperthyroidism 8866 0.43 1822 0.27 7044 0.47 0.23
 Intrauterine growth restriction 8866 1.2 1822 1.4 7044 1.2 0.37
 Placenta abruption 8866 0.20 1822 0.0 7044 0.26 0.035a
Parity (Primipara, %) 8783 39.4 1789 37.8 6994 39.8 0.12
Infertility treatment (Yes, %) 8814 4.6 1812 5.9 7002 4.3 0.0059
Fish intake (g/day) 8757 29.1 (0.8–919) 1788 1788 28.3 (1.2–612) 6969 29.4 (0.8–919) 0.11
Meat intake (g/day) 8762 54.6 (0.4–1740) 1789 55.5 (0.4–1581) 6973 54.3 (1.5–1740) 0.21
Supplemental use (%)
 Any kind 8774 38.8 1793 34.2 6981 40.0 <0.0001
 EPA and/or DHA 8773 2.2 1792 2.5 5981 2.1 0.30
Breakfast skipper (Skipper, %) 8756 13.8 1788 14.8 6968 13.5 0.14
Housewife (Yes, %) 8742 44.0 1787 50.6 6955 42.3 <0.0001
Number of live births
 Singleton births (%) 8873 99.2 1823 99.2 7050 99.1 0.69
Gestational age at birth (day) 8857 274.1 ± 11.8 1819 273.6 ± 13.5 7038 274.3 ± 11.3 0.025
 Preterm births (<37) (%) 8857 5.5 1819 5.4 7038 5.5 0.93
Sex (Male, %) 8865 51.0 1822 51.6 7043 50.9 0.35
Type of delivery (Transvaginal, %) 8847 82.2 1819 81.9 7028 82.2 0.74
Birth weight (g, Singleton births)
 All 8850 3046 ± 441 1818 3031 ± 479 7032 3050 ± 431 0.12
 Male 4481 3095 ± 433 939 3076 ± 485 3580 3089 ± 433 0.43
 Female 4289 3010 ± 427 876 2984 ± 468 3450 3008 ± 424 0.15
 Low birth weight (<2500 g) (%) 8850 8.2 1818 9.8 7032 7.8 0.005
  1. Mean ± SD or median (min-max)
  2. aFisher exact test