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
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
Alcohol consumption after delivery (n=90 428)<0.001
 Never drank86.286.987.991.7
 Ex-drinker who quit before pregnancy5.
Medical history of bronchial asthma

(n=91 837)
Mental health (K6) during pregnancy
(≥13 points) (n=91 002)<0.001
Mental health (EPDS) after delivery
(≥9 points) (n=89 279)
Self-reported mother’s health status after delivery (n=90 332)<0.001
 Very good40.743.844.345.8
Problems at delivery
 Apgar score <7 at 1 min (n=90 274)<0.001
 Physical anomalies in neonates3.<0.001
 Neonatal referral (n=89 843)<0.001
Siblings living with the child after delivery<0.001
Primary caregiver is child’s mother

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

(n=90 743)
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.
Partner participation†<0.001
 Inactive participation8.
 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.