Table 1

Baseline characteristics of samples

The lost-to-follow-up
(n=5675), %
Resumed group
(n=1136), %
Discontinued group
(n=3879), %
Continued group
(n=82 727), %
P value
Age at delivery (n=93 333)<0.001
 <2523.722.019.910.4
 25–2930.133.730.129.3
 30–3426.527.331.235.5
 ≥3519.717.018.824.8
Smoking habits after delivery (n=90 337)<0.001
 Never smoked41.447.547.759.8
 Ex-smoker who quit before pregnancy20.421.520.522.6
 Ex-smoker who quit after pregnancy24.819.723.214.0
 Smoker13.411.38.63.6
Alcohol consumption after delivery (n=90 428)<0.001
 Never drank86.286.987.991.7
 Ex-drinker who quit before pregnancy5.84.96.34.4
 Drinker8.08.25.73.9
Medical history of bronchial asthma

(n=91 837)
13.412.312.310.7<0.001
Mental health (K6) during pregnancy
(≥13 points) (n=91 002)
6.56.44.23.0<0.001
Mental health (EPDS) after delivery
(≥9 points) (n=89 279)
19.317.516.414.0<0.001
Self-reported mother’s health status after delivery (n=90 332)<0.001
 Very good40.743.844.345.8
 Good27.527.828.028.2
 Fair26.823.124.022.6
 Poor4.95.13.53.2
Problems at delivery
 Apgar score <7 at 1 min (n=90 274)3.93.72.02.1<0.001
 Physical anomalies in neonates3.43.42.12.2<0.001
 Neonatal referral (n=89 843)8.07.25.85.5<0.001
Siblings living with the child after delivery<0.001
 038.341.941.747.9
 135.135.335.934.6
 ≥226.622.822.417.5
Primary caregiver is child’s mother

(n=90 436)
98.598.998.999.3<0.001
‘Satogaeri bunben’* (n=90 043)41.944.745.049.8<0.001
Educational status (≥13 years)

(n=90 743)
46.550.552.865.4<0.001
Family income per year (n=84 693)<0.001
 <4 million yen50.751.946.339.2
 4–12 million yen47.246.152.359.0
 ≥12 million yen2.12.01.41.8
Partner participation†<0.001
 Non-participation61.659.955.247.1
 Inactive participation8.43.82.30.7
 Active participation30.036.342.552.2
  • *‘Satogaeri bunben’ refers to the mother returning to her parents’ home for delivery.

  • †If the partner agreed to participate but did not return the questionnaire, his/her participation was classified as passive participation. If the partner returned the questionnaire, his/her participation was classified as active participation. Partners who did not agree to participate or could not be contacted to request participation were classified under ‘non-participation’.

  • EPDS, Edinburgh Postnatal Depression Scale; K6, Kessler Psychological Distress Scale.