Table 3.
Effects of maternal age (β) in regression models for birth weight stratified by parity and sex of neonates.
| Age Groups [Years] | Primiparas | Multiparas | ||||||
|---|---|---|---|---|---|---|---|---|
| Boys | Girls | Boys | Girls | |||||
| β with 95% CI [Grams] | † p | β with 95% CI [Grams] | † p | β with 95% CI [Grams] | † p | β with 95% CI [Grams] | † p | |
| Model 1 (crude): maternal age | ||||||||
| 20–24 | −11.4 (−14.1, −8.8) | *** | −10.6 (−13.2, −8.0) | *** | −71.9 (−75.9, −67.9) | *** | −71.1 (−74.9, −67.2) | *** |
| 25–29 | Reference | Reference | Reference | Reference | ||||
| 30–34 | −36.1 (−39.0, −33.2) | *** | −34.9 (−37.8, −32.1) | *** | −0.1 (−2.7, 2.6) | NS | 6.3 (3.7, 8.9) | *** |
| 35–39 | −92.8 (−97.9, −87.6) | *** | −94.5 (−99.5, −89.5) | *** | −41.1 (−44.4, −37.9) | *** | −29.7 (−32.9, −26.6) | *** |
| 40–44 | −168.3 (−181.8, −154.9) | *** | −178.0 (−190.9, −165.4) | *** | −106.2 (−112.3, −100.0) | *** | −83.6 (−89.6, −77.6) | *** |
| ≥45 | −229.0 (−295.5, −162.5) | *** | −331.5 (−403.3, −259.6) | *** | −179.7 (−208.3, −151.0) | *** | −179.1 (−206.7, −151.5) | *** |
| †† p | *** | *** | *** | *** | ||||
| ††† p | ** | *** | *** | *** | ||||
| Model 2: maternal age adjusted for biological factors | ||||||||
| 20–24 | −13.3 (−15.6, −10.9) | *** | −13.3 (−15.6, −11.0) | *** | −60.6 (−64.1, −57.0) | *** | −59.4 (−62.9, −55.9) | *** |
| 25–29 | Reference | Reference | Reference | Reference | ||||
| 30–34 | −20.8 (−23.4, −18.3) | *** | −21.1 (−23.6, −18.6) | *** | 7.6 (5.3, 10.0) | *** | 11.6 (9.3, 13.9) | *** |
| 35–39 | −52.8 (−57.4, −48.2) | *** | −59.4 (−63.9, −54.9) | *** | −13.8 (−16.7, −10.9) | *** | −7.0 (−9.9, −4.2) | *** |
| 40–44 | −100.4 (−112.3, −88.6) | *** | −111.0 (−122.5, −99.6) | *** | −51.9 (−57.4, −46.5) | ** | −35.8 (−41.2, −30.4) | *** |
| ≥45 | −139.6 (−198.1, −81.0) | *** | −200.1 (−264.0, −136.1) | *** | −109.7 (−135.1, −84.4) | *** | −109.8 (−134.6, −85.1) | *** |
| †† p | *** | *** | *** | *** | ||||
| ††† p | * | *** | *** | *** | ||||
| Model 3: maternal age adjusted for biological and demographic factors | ||||||||
| 20–24 | −7.1 (−9.5, −4.7) | *** | −7.0 (−9.3, −4.6) | *** | −44.3 (−47.8, −40.7) | *** | −44.0 (−47.5, −40.5) | *** |
| 25–29 | Reference | Reference | Reference | Reference | ||||
| 30–34 | −18.5 (−21.1, −15.9) | *** | −18.9 (−21.4, −16.4) | *** | 6.4 (4.1, 8.7) | *** | 10.3 (8.0, 12.6) | *** |
| 35–39 | −47.0 (−51.5, −42.4) | *** | −53.8 (−58.3, −49.4) | *** | −10.8 (−13.7, −8.0) | *** | −4.3 (−7.1, −1.4) | ** |
| 40–44 | −93.0 (−104.8, −81.1) | *** | −104.1 (−115.6, −92.6) | *** | −45.0 (−50.5, −39.6) | *** | −29.8 (−35.2, −24.4) | *** |
| ≥45 | −130.0 (−188.5, −71.5) | *** | −192.7 (−256.6, −128.7) | *** | −103.2 (−128.5, −77.9) | *** | −105.6 (−130.3, −80.9) | *** |
| †† p | *** | *** | *** | *** | ||||
| ††† p | * | *** | *** | *** | ||||
| Model 4: maternal age adjusted for biological, demographic, and social factors | ||||||||
| 20–24 | 5.3 (2.7, 7.9) | *** | 4.9 (2.4, 7.4) | *** | −16.5 (−20.1, −12.9) | *** | −18.0 (−21.6, −14.5) | *** |
| 25–29 | Reference | Reference | Reference | Reference | ||||
| 30–34 | −20.1 (−22.7, −17.6) | *** | −20.5 (−23.0, −18.0) | *** | −2.0 (−4.4, 0.3) | NS | 2.1 (−0.2, 4.4) | NS |
| 35–39 | −47.7 (−52.3, −43.2) | *** | −54.6 (−59.1, −50.2) | *** | −16.5 (−19.4, −13.7) | *** | −9.9 (−12.7, −7.1) | *** |
| 40–44 | −92.3 (−104.2, −80.5) | *** | −103.5 (−115.0, −92.1) | *** | −44.3 (−49.7, −38.8) | *** | −29.6 (−35.0, −24.3) | *** |
| ≥45 | −131.0 (−189.4, −72.6) | *** | −192.3 (−256.1, −128.5) | *** | −99.4 (−124.6, −74.3) | *** | −101.9 (−126.6, −77.3) | *** |
| †† p | *** | *** | *** | *** | ||||
| ††† p | NS | *** | *** | *** | ||||
† p-value for given maternal age category versus reference category; †† p-value for linear term; ††† p-value for quadratic term; CI—confidence interval; *** p ≤ 0.001; ** p ≤ 0.01; * p ≤ 0.05; NS—not significant.