Strengths and Limitations
A homogeneous group of patients was selected from women giving birth to
the first or subsequent child in a public tertiary hospital with one of
the largest number of deliveries per year in Poland.
The limitation of the study may be its one-center character. However,
the use of electronic medical records allowed for high reliability and
credibility of the research material collected in the center. The period
of the study, covering 6 years, does not preclude a possible change in
the standard of conduct in the course of the study, which may affect the
results of the analysis. However, it allowed the recruitment of a large
number of patients to the study. The studied group included 394 patients
were over 40 years of age which amounted to 1.5% of the population.
Probably, for this reason, no logistic regression model was built, in
which age would be a significant risk factor in this subgroup of
patients. The interpretation of the results for women over 40 years of
age should be cautious. Patients who had experienced the study endpoint
in the previous pregnancy were not excluded from the study group. There
was no sufficient data on the course of previous pregnancies and
deliveries, except for previous cesarean section; thus, the results
should be interpreted with caution. Due to the lack of data, the
socioeconomic status, educational level, height and body mass index were
not evaluated. The authors are aware of a potential correlation between
the above factors and the risk of adverse perinatal outcome [17,
18]. The use of nicotine and alcohol is not taken into account;
however, according to the available data, this should not interfere with
the results of the study [19, 20]. Advanced maternal age is not
associated with more frequent smoking. On the contrary, nicotinism is
more common in pregnant women under 20 years of age [16].