Pregnancy outcome in primiparae of advanced maternal age

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Abstract

Objective

To investigate the impact of maternal age on singleton pregnancy outcome, taking into account intermediate and confounding factors.

Study design

In this population-based retrospective cohort study, perinatal data of primiparous women aged 35 years or more (n = 2970), giving birth to a singleton child of at least 500 g, were compared to data of primiparous women aged 25–29 years old (n = 23,921). Univariate analysis was used to assess the effect of maternal age on pregnancy outcomes. The effects of intermediate (hypertension, diabetes and assisted conception) and confounding factors (level of education) were assessed through multivariable logistic regression analysis.

Results

Older maternal age correlated, independently of confounding and intermediate factors, with very preterm birth (gestational age <32 weeks) [adjusted odds ratio (AOR) 1.51, 95% confidence intervals (CI) 1.04–2.19], low birth weight (birth weight <2500 g) (AOR 1.69, 95% CI 1.47–1.94) and perinatal death (AOR 1.68, 95% CI 1.06–2.65).

Conclusion

Maternal age is an important and independent risk factor for adverse pregnancy outcome.

Introduction

Maternal age has been repeatedly scrutinized as a putative risk factor for adverse pregnancy outcome [1], [2], [3], [4], [5], [6], [7]. Though the preponderance of these studies tend to indicate that women of advanced (≥35 years) and high (≥40 years) maternal age do incur a significantly increased risk of obstetric complications and interventions, it has also been argued that current evidence on the association between maternal age and perinatal outcome remains largely clouded by age-related confounding factors [5], [8], [9], [10]. Type II diabetes and hypertension show an incremental increase with advancing maternal age and therefore act as mediating variables on the pathway between age and pregnancy outcome [5]. In this manner, it remains unclear how much maternal age itself contributes to poor pregnancy outcome rather than age-related co-morbidity. This perspective encouraged us to investigate the effect of confounding (level of education) and mediating variables (hypertension, diabetes, mode of conception) in the relationship between maternal age and pregnancy outcome.

Section snippets

Materials and methods

Data were obtained from the existing computer files of a regional population-based perinatal database, the Flemish Study Centre for Perinatal Epidemiology (SPE) [11]. For each newborn of at least 500 g, an official and coded perinatal form was completed (most often by the midwife) and sent to the SPE, where all data were controlled by an error detection program and feedback was provided [12]. A qualitative assessment of SPE-data showed that there was less than five percent discrepancy between

Results

In 2002–2003, the SPE registered 118,094 deliveries of neonates ≥500 g. Out of these, 2970 (2.5%) were singletons in primiparae ≥35 years and 23,921 (20.2%) singletons in women between 25 and 29 years. Patient characteristics of both age-groups were summarized in Table 1. In older women, pregnancy was more likely to be obtained by assisted conception (P < 0.001). Compared with younger primiparae, older women were more likely to suffer from risk factors in pregnancy, such as hypertension and

Comment

Even after adjusting for hypertension, diabetes, level of education and mode of conception, maternal age proved an independent risk factor for adverse pregnancy outcome.

This study was based on a large sample size and is one of the few population-based studies. In addition, it was possible to adjust for intermediate and confounding factors. Only a small number of previous studies corrected their data for mode of conception [4].

Limitations of our study include that data concerning gravidity, body

Acknowledgments

We would like to thank all Flemish gynaecologists and midwives for their contribution in the SPE-registration. We also acknowledge the scientific committee of the SPE and the Flemish Ministry of Health for the access to their data, as well as Vanessa De Bolle and Sylvie Vermeren for their committed registration.

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