Table 3.
Multivariable associations of preterm birth and multiple gestation of the first birth with natural menopause among 69,880 parous participants in the Nurses’ Health Study II, 1989–2019.
| Adverse pregnancy outcome | Early natural menopause (<45 years) | Natural menopausea | |||
|---|---|---|---|---|---|
| Model 1b | Model 2c | Model 2c | |||
| Cases | Person-years | HR (95% CI) | HR (95% CI) | HR (95% CI) | |
| Timing of birth in 2 categories (weeks) | |||||
| Term (≥37) | 1588 | 1,144,708 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| Preterm (<37) | 175 | 104,971 | 1.18 (1.01, 1.38) | 1.14 (0.98, 1.34) | 1.00 (0.97, 1.04) |
| Timing of birth in 3 categories (weeks) | |||||
| Term (≥37) | 1588 | 1,144,708 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| Moderate preterm (>32 to <37) | 133 | 79,998 | 1.17 (0.98, 1.39) | 1.16 (0.97, 1.39) | 1.01 (0.97, 1.05) |
| Very preterm (≥20 to <32) | 42 | 24,973 | 1.23 (0.91, 1.68) | 1.09 (0.80, 1.48) | 0.98 (0.91, 1.05) |
| P value for trendd | 0.04 | 0.18 | 0.78 | ||
| Per 1 week increase in gestational age | 0.98 (0.96, 1.00) | 0.99 (0.97, 1.01) | 1.00 (1.00, 1.01) | ||
| Preterm birth by gestation type | |||||
| Term singleton | 1569 | 1,136,209 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| Term multiple gestation | 19 | 8499 | 1.48 (0.94, 2.34) | 1.65 (1.05, 2.60) | 1.46 (1.31, 1.63) |
| Preterm singleton | 152 | 97,880 | 1.11 (0.94, 1.31) | 1.07 (0.90, 1.26) | 0.99 (0.96, 1.03) |
| Preterm multiple gestation | 23 | 7091 | 2.23 (1.47, 3.37) | 2.38 (1.57, 3.61) | 1.21 (1.07, 1.36) |
| Preterm birth by labor type | |||||
| Term, spontaneous | 830 | 625,901 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| Preterm, spontaneous | 76 | 48,761 | 1.14 (0.90, 1.44) | 1.11 (0.88, 1.41) | 1.08 (1.03, 1.14) |
| Term, induced | 224 | 158,914 | 1.02 (0.88, 1.18) | 1.00 (0.86, 1.16) | 0.94 (0.91, 0.97) |
| Preterm, induced | 19 | 11,415 | 1.17 (0.74, 1.85) | 1.10 (0.70, 1.74) | 0.91 (0.82, 1.01) |
| Term, not specified | 534 | 359,893 | 1.06 (0.95, 1.19) | 1.08 (0.96, 1.20) | 1.01 (0.98, 1.03) |
| Preterm, not specified | 80 | 44,795 | 1.29 (1.03, 1.63) | 1.25 (0.99, 1.58) | 0.93 (0.88, 0.98) |
Abbreviations: CI, confidence interval; HR, hazard ratio; multiple gestation, twins, triplets, or higher-order multiples; preterm, gestational age <37 completed weeks; term, gestational age ≥37 completed weeks.
Onset of natural menopause: HR>1 indicates younger age at menopause; HR<1 indicates older age menopause.
Adjusted for age at first birth (continuous), age at baseline (continuous), race/ethnicity (African American, Hispanic, Asian, Caucasian, or other), maternal and paternal education (<9, 9–11, 12, 13–15 or ≥16 years), and pre-pregnancy factors of age at menarche (≤9, 10, 11, 12, 13, 14, 15, 16, or ≥17 years), physical activity at 18 years of age (never, 1–3, 4–6, 7–9, or 10–12 months per year), body mass index (weight (kg)/height (m)2; 15.0-<18.5, 18.5-<25.0, 25.0-<30.0, or 30.0-<50.0), alcohol consumption (none, ≤1/week, 2–6/week, or ≥1/day), smoking (never, past, or current smoker), oral contraceptive use (none, <2, ≥2-<4, or ≥4 years), and infertility due to ovulatory disorder (no or yes).
Additionally adjusted for post-first birth factors of body mass index (weight (kg)/height (m)2; <18.5, 18.5-<25.0, 25.0-<30.0, or ≥30.0 kg/m2), alcohol consumption (none, ≤1/week, 2–6/week, or ≥1/day), smoking status (never, past, or current smoker), infertility due to ovulatory disorder (no or yes), parity (continuous), and breastfeeding (<1, 1–3, >3–6, >6–12, >12–18, >18–24, >24–36, or >36 months).
Linear trends were assessed by modeling category midpoints as a continuous variable.