Interpretation
Ravelli et al . previously showed that the risk of a low 5-minute
Apgar score <7 among term singletons in the Netherlands
increased in the period 2010-2014 (from 9.9/1000 in 2010 to 10.9/1000 in
2014, p< 0.001).(13, 14) This observation was worrisome
because it had been reported in numerous studies that a low Apgar score
is associated with adverse neonatal outcome.(8-12, 21, 22) However,
studies reporting more recent data on low Apgar scores are currently
lacking for the Netherlands. Overall, the rates of low Apgar scores that
we found in this study are in line with the literature. We report that
1.20% of (near) term liveborn singletons had a 5-minute Apgar score
<7. A study from the United Kingdom found similar results:
1.54% of all liveborn infants had an Apgar score <7.(23) The
EURO-Peristat project, covering twenty-three countries or regions in
Europe, reported rates between 0.3-2.4% for Apgar scores <7
for the period 2004 to 2010.(24) For the more recent period 2015-2019,
unfortunately, data on Apgar scores were not reported by the
EURO-Peristat project.(25)
A low 5-minute Apgar score was chosen as main outcome measure of this
study. The Apgar score has been widely embedded into clinical practice
as an accepted method for standardised assessment of the neonate
immediately after birth on the basis of heart rate, respiration, colour,
muscle tone and reflex irritability.(6) There are numerous factors,
apart from birth asphyxia, that can influence Apgar scores, including
maternal medication or anaesthesia, gestational age, congenital
malformations, trauma, and interobserver variability of the Apgar
assessment.(26, 27) A low Apgar score alone is not sufficient to
diagnose birth asphyxia.(7) However, in term infants without congenital
malformations a low 5-minute Apgar score most likely reflects birth
asphyxia.(8) In this study, including only (near) term singletons
without congenital malformations, we therefore used a low 5-minute Apgar
score as proxy for birth asphyxia.
A major limitation of this study is the lack of information on long-term
outcomes. However, it has been shown in large population-based studies
that low Apgar scores are well correlated with long-term outcomes in a
dose-dependent manner across the entire range of Apgar scores. Prior
studies showed a strong association between 5-minute Apgar scores below
7 and cerebral palsy, epilepsy, special needs and cognitive
impairment.(8-12, 21, 22). Selvaratnam et al. recently showed
that there is an adverse relation between the 5-minute Apgar score and
poor developmental and educational outcomes. The least favourable
outcomes were seen for infants with an Apgar score of 0 to 3, compared
to those with an Apgar score of 10. Increasingly favourable outcomes
were observed for infants with Apgar closer to 10, but Apgar scores of
7, 8 and 9 were also associated with poorer educational outcomes.(28)
The increase in low 5-minute Apgar scores that we observed in our study
is therefore relevant and needs further attention.
Our observations suggest an increase in infants with birth asphyxia. The
trends observed in low Apgar scores are supported by the increasing
trends in NICU admissions and low umbilical artery pHs over the past
decade. We can only speculate about the reasons for these observations.
The highest PARs were found for nulliparity, epidural analgesia,
emergency caesarean section, instrumental vaginal delivery, prolonged
second stage of labour, male sex and delivery in secondary care.
Nulliparity and male sex are risk factors that cannot be changed, but
the other variables can be influenced and are therefore of special
interest. It is remarkable that the intervention subgroups of
instrumental vaginal delivery and emergency caesarean section show the
highest increase in low 5-minute Apgar scores. For Apgar score
<7 we observed a relative increase of 52.4% and 63.3%,
respectively, compared to an increase of 36.5% in the total cohort. For
Apgar score <4, this was 33.3% and 30.1%, respectively,
compared to 11.8% in the total cohort. Both interventions are generally
performed when fetal distress is suspected. In our study, these
interventions were less frequently performed over the last decade, but
these intervention subgroups showed a relatively high increase in low
Apgar scores. There are two possible explanations for these
observations. The first explanation is a better selection of infants
with fetal distress over time due to improved fetal monitoring, with the
interventions only being performed when there is a strong medical
indication. However, a second potential explanation could be a more
reluctant attitude towards obstetric interventions emergency caesarean
section and instrumental vaginal delivery. This reluctance might cause a
delay in time to intervention, and thus have a negative impact on the
outcome of pregnancies resulting in more infants with lower Apgar
scores. These two explanations, or a combination of both, and residual
confounding may play a role, but the current study design, being an
observational study cohort, limited us to investigate causality.
The level of care was studied because of the unique Dutch maternity care
system. As expected, in primary care, with only low-risk pregnancies,
the overall risk of a low Apgar score was remarkably low. The increase
in low Apgar scores (<7 and <4) was relatively high
in secondary care compared to primary care. This could implicate that
health care factors, implemented in secondary care (such as obstetric
interventions), are the most relevant.