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Cho, Jo, Cho, Eom, Rhie, and Lee: Advanced Maternal Age and Weight at Birth in Newborn Infants: Distribution and Clinical Characteristics
Original Article

Korean J Perinatol 2014;25(4):276-283.

Published online: 21 December 2014

DOI: https://doi.org/10.14734/kjp.2014.25.4.276

Advanced Maternal Age and Weight at Birth in Newborn Infants: Distribution and Clinical Characteristics

Kee Hyun Cho, M.D.1, Heui Seung Jo, M.D.1, Sung-Il Cho, M.D.2, Younghyon Andrew Eom3, Seonkyeong Rhie, M.D.1, Kyu Hyung Lee, M.D.1

1Department of Pediatrics, CHA Bundang Medical Center, CHA University, Seongnam, Korea

2Graduate School of Public Health, Seoul National University, Seoul, Korea

3Deparment of Molecular Biology and Biochemistry, Wesleyan University, United States, Seongnam, Korea

Received 29 August 201426 September 2014       Accepted 8 October 2014

Copyright © 2014 Korean Society of Perinatology

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

This study aimed to compare the neonatal outcome by quantifying the effect of maternal age on low birth weight (LBW).

Methods

We reviewed the medical records of 12,742 newborn infants born at CHA Bundang Medical Center from January 2009 to December 2013. Infants were compared after being categorized by the following 4 maternal age groups - <25 years (N=343), 25-34 years (N=8,573), 35-39 years (N=3,186), ≥40 years (N=640). Statistical analysis included use of logistic regression models with likelihood ratio tests for interaction effects.

Results

Incidence of perinatal complications tended to increase significantly with maternal age - gestational diabetes mellitus (GDM;P<0.001), pregnancy induced hypertension (PIH;P=0.019), placenta previa (P<0.001), and cesarean section (P<0.001). Compared to the age group of 25-34 years (reference group), no significant differences were found in age group of 35-39 year [odds ratio (OR)=0.945, 95% confidence interval (CI) 0.847-1.056, P=0.319] and ≥40 years (OR=0.841, 95% CI 0.671-1.056, P=0.136) for LBW. After adjusted by gestational age, incidence of in vitro fertilization (IVF), and perinatal complications, maternal age was not found to be an independent risk factor for LBW (OR=0.847, 95% CI 0.730-0.982, P=0.028 for 35-39 years, and OR=0.652, 95% CI 0.481-0.884, P=0.006 for ≥40 years).

Conclusion

Although incidence of perinatal complications tends to increase with age, neonatal outcome of age group of ≥35 years measured by incidence of LBW infants was not unfavorable compared to the reference group. The result suggests that the thorough prenatal care may be more important than the maternal age itself.

Keywords: Maternal age, Low birth weight, Gestational age

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Fig. 1.
The progress in proportion of births according to maternal age in CHA Bundang Medical Center from 2009-
kjp-25-276-f1.tif
Fig. 2.
Distribution of gestational age of infants in relation to maternal age (no significant linear correlation exist, R2= 0.0015).
kjp-25-276-f2.tif
Fig. 3.
Distribution of birth weight of infants in relation to maternal age (no significant linear correlation exists, R2= 0.0038).
kjp-25-276-f3.tif
Table 1.
Maternal characteristics and perinatal complications according to age groups
<25 years (N=343) 25-34 years (N=8,573) 35-39 years (N=3,186) ≥40 years (N=640) P*
GDM (%) 4.1 4.7 7.9 10.2 <0.001
PIH (%) 4.4 3.2 3.8 5.2 0.019
Placenta previa (%) 0.6 2.8 3.7 6.1 <0.001
Placenta abruption (%) 1.5 0.7 0.6 1.1 0.895
PROM (%) 17.2 14.2 10.2 11.4 <0.001
Cesarean section (%) 28.0 38.2 47.6 54.4 <0.001
Multiple gestation (%) 9.9 13.1 14.8 9.2 0.707
IVF (%) 6.4 14.1 22.8 18.8 <0.001

Abbreviations: GDM, gestational diabetes mellitus; PIH, pregnancy-induced hypertension; PROM, premature rupture of membranes; IVF, in vitro fertilization

* P-values were calculated by linear by linear association

Table 2.
Gestational age and birth weight according to maternal age
<25 years (N = 343) 25-34 years (N = 8,573) 35-39 years (N = 3,186) ≥40 years (N = 640) P*
Gestational age (week) 0.006
<32 (%) 1.7 1.8 1.2 1.7
32-34+6 (%) 9.9 4.5 4.3 4.4
35-36+6 (%) 21.6 13.8 14.2 14.5
≥37 (%) 66.8 80.0 80.4 79.4
Birth weight (g) 0.059
<1,000 (%) 0.3 0.4 0.3 0.8
1,000-1,499 (%) 1.2 1.0 0.8 0.8
1,500-2,499 (%) 18.7 15.4 14.9 13.0
≥2,500 (%) 79.9 83.2 84.0 85.5

* P-values were calculated by linear by linear association

Table 3.
Multivariate logistic regression analysis for low birth weight
Maternal age Unadjusted Adjusted
Odds ratio* 95% Confidence interval P Odds ratio† 95% Confidence interval P
<25 years 1.246 0.951-1.633 0.110 0.742 0.506-1.086 0.125
35-39 years 0.945 0.847-1.056 0.319 0.847 0.730-0.982 0.028
≥40 years 0.841 0.671-1.056 0.136 0.652 0.481-0.884 0.006

* Reference group for calculation of odds ratios is age group of 25-34 years

† Values are adjusted by gestational age, GDM, PIH, placenta previa, PROM, cesarean section, and IVF Abbreviations: GDM, gestational diabetes mellitus; PIH, pregnancy-induced hypertension; PROM, premature rupture of membranes; IVF, in vitro fertilization

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