Interpretation
In the majority of literature on the subject, the assessment of the
influence of mother’s age on the course of pregnancy and delivery is
based on a comparative assessment of complications occurring in
different age groups. The most frequently compared groups are 35-39 and
over 40 years, and the control group is composed of younger patients,
also in the age groups 20-24, 25-29, 20-34 years. Grouping by age
certainly facilitates the interpretation and presentation of results.
Data averaging in the 5-year range (most frequently used in the
literature) may, however, it harms the accuracy of the study and the
strength of scientific evidence [21-24]. Age as a discrete variable
allows a more precise determination of its impact on the risk of the
endpoint.
Despite many studies confirming the adverse effect of increasing
pregnant age on the incidence of specific complications of the course of
pregnancy and delivery and perinatal failures, the standard of prenatal
and perinatal care was not introduced into the clinical practice in an
increasing number of patients over 35 years of age. There are limited
reports that include age as a discrete variable in which attempts were
made to find a safe limit regardless of age group, but the results
suggest a linear increase in adverse perinatal outcomes. Importantly, in
subsequent publications, a coherent threshold with significantly
increased risk of obstetric complications was not specified, which
confirms the thesis about the relevance of the methodology of
statistical analysis adopted in this study [8, 25, 26]. Determining
the exact age at which the risk of complications significantly increases
is difficult. According to some researchers, a statistically significant
difference in the percentage of complications occurs after 35 years of
age [27, 28], according to others only after 40 years of age
[29]. Some studies suggest that the risk of complications increases
with age, and this increase is linear, not threshold [8, 25]. Kenny
et al. suggest such dependence; however, in their study, the group was
divided into 5-year age ranges, which makes it difficult to confirm this
hypothesis [8]. In a similarly constructed study, Joseph et al.
reported an increase in the risk of perinatal morbidity and mortality in
the 35-39 group (OR 1.46, 95% CI 1.11-1.92, p = 0.007) and at least 40
years (OR 1.95, 95% CI 1.13-3.35, p = 0.02) compared to 20-24 years
[30]. In turn, Ezra et al. compared perinatal results in patients
over 40 years of age with patients aged 35-40. They found a similar
perinatal risk in both groups, nulliparous and multiparous women
[31].
In this study, showing the significant increase in the risk of a primary
endpoint in the entire population (treating age as a discrete variable,
without the division of subjects into age groups), the importance of age
as a risk factor was confirmed. It was possible due to the inclusion of
a large group of women in the analysis, which distinguishes the study.
It should be emphasized that the importance of a woman’s age in
obstetric prognosis changes in the subsequent years of her life.
Patients included in the study were a group of patients with low risk of
complications of pregnancy and delivery. Nevertheless, the risk of the
primary endpoint with each year increased more and more with the age of
the patients. The importance of age as a risk factor changes over time,
as illustrated in the graph in Figure 3.