Table 5 Adjusted ORs (95% CIs) for the association between age at menarche and PTB, stratified by parity.

From: Age at menarche and prevalence of preterm birth: Results from the Healthy Baby Cohort study

Age at menarche (years)

Parity = 1 (n = 9396)

Parity ≥2 (n = 1620)

P for interaction

ORa (95% CI)

ORb (95% CI)

ORa (95% CI)

ORb (95% CI)

≤11

1.69 (1.39, 2.06)

1.69 (1.15, 2.48)

1.60 (1.06, 2.41)

1.54 (0.67, 3.56)

0.934

12

1.18 (1.05, 1.33)

1.18 (0.93, 1.50)

1.15 (0.74, 1.79)

1.16 (0.72, 1.86)

13

1.00 (Reference)

1.00 (Reference)

1.00 (Reference)

1.00 (Reference)

14

0.85 (0.74, 0.97)

0.84 (0.65, 1.09)

0.86 (0.69, 1.08)

0.89 (0.57, 1.39)

≥15

1.08 (0.93, 1.26)

1.08 (0.80, 1.46)

1.05 (0.82 1.33)

1.00 (0.62, 1.62)

  1. Abbreviation: OR, odds ratio; CI, confidence intervals; PTB, preterm birth. aAdjusted for maternal age, educational level, and occupational status. bAdjusted for maternal age, educational level, occupational status, alcohol consumption before pregnancy, smoking before pregnancy, passive smoking during pregnancy, physical activity during pregnancy, parity, history of spontaneous abortion, history of induced abortion, the use of assisted reproductive technologies, diabetes during pregnancy, and hypertension during pregnancy.
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