OTHER CAUSES PREDISPOSING TO INCREASED NIGHTTIME PERINATAL MORTALITY HAVE NOT BEEN EXCLUDED
Dear Editor
The unstated premise of the article by Heller et al1 that the incidence of
perinatal death due to intrapartum asphyxia in low risk pregnancies may
serve as a sensitive measure of the quality of peripartum care delivered
is appealing 2. However the proposition by Heller that the observed higher
nocturnal perinatal mortality in a selected population was a result of
substandard care was not justified in the article.
Firstly, a comprehensive index case record interrogation was absent.
The Confidential Enquiry in to Stillbirths and Deaths in Infancy (CESDI) 3
adopts the gold standard method of a multi-disciplinary scrutiny of the
records to ensure diagnostic accuracy as well as quantification of any
substandard care involved.
Secondly, imprecise selection criteria ensured the sample population
was heterogeneous in terms of pregnancy risk and method of delivery.
Further bias arose as Heller’s early neonatal death rate (0.15 per 1000
births selected) represented only a small fraction of the unstated overall
early neonatal death rate (3.1 per 1000 live births found in a similar
population by CESDI 2).
Thirdly, recommended criteria necessary before a diagnosis of acute
perinatal asphyxia can be made 4 were not adopted by Heller’s article.
Furthermore it is noteworthy that deaths classified as ‘asphyxia related’
occurring as a result of hypoxia during labour do not necessarily mean
that the hypoxia was preventable.
More useful information would have been derived if the crude early
neonatal death rate data were reclassified in a pathophysiological cause-
specific manner e.g. adopting the amended Wigglesworth classification 5 or
incorporated birth weight/gestation specific mortality. Such cause-
specific mortality relationships better identify the exact contribution of
antepartum and intrapartum risk factors to infant mortality and whether
there is any diurnal variation to their incidence. Importantly, Heller’s
article could not demonstrate whether high-risk pregnancies present more
frequently at night. Case-control analysis of matched cases with similar
obstetric-neonatal factors and delivery centres but differing by delivery
time could further reveal the contribution of delivery time to perinatal
death and whether this relationship is cause-specific.
Ultimately the identification of pregnancies without substandard care
or obstetric risk that still incur a significantly higher nocturnal
perinatal mortality pose a serious concern which perhaps represents a
manifestation of the maternal-fetal physiology specific to this period
which at present is unknown. Antepartum "unexplained" fetal death might
also enter into this subgroup, which, despite advances in obstetric
medicine and fetal monitoring, comprises the majority of perinatal deaths.
Standards of health care delivery are always under inspection (e.g.
Clinical Governance, the media) and thus comprehensive evaluation, with
consideration given to other possible causes, is essential before such
‘human’ issues are drawn into the causality equation for adverse outcome
occurring at night.
Yours sincerely
Rajesh Varma MA MRCOG DFFP Senior SHO Obstetrics and Gynaecology
Srinivas Vindla MD MRCOG Specialist Registrar Obstetrics and
Gynaecology
Lawrence Mascarenhas MD MRCOG M.Ed Consultant Obstetrician and
Gynaecologist
Department of Obstetrics and Gynaecology, Queens Medical Centre,
Nottingham, NG7 2UH
1. Heller G, Misselwitz B, Schmidt S. Early neonatal mortality, asphyxia
related deaths, and timing of low risk births in Hesse, Germany, 1990-98:
observational study. BMJ 2000; 321: 274-5
2. Field DJ, Smith H, Mason E, Milner AD. Is perinatal mortality still a
good indicator of perinatal care? Paediatr Perinat Epidemiol 1988; 2:213-9
3. Confidential Enquiry into Stillbirths and Deaths in Infancy. Sixth
Annual Report. London: Maternal and Child Health Research Consortium. 1999
4. American Academy of Pediatrics, American College of Obstetricians and
Gynecologists. Relationship between perinatal factors and neurologic
outcome. In: Poland RL, Freeman RK, editors. Guidelines for perinatal
care. 3rd ed. Elk Grove Village (IL): American Academy of Pediatrics;
1992.pp 221-4.
5. Keeling JW, MacGillivray I, Golding J, Wigglesworth J, Berry J, Dunn
PM. Classification of perinatal death. Arch Dis Child 1989; 64: 1345-1351
Rapid Response:
OTHER CAUSES PREDISPOSING TO INCREASED NIGHTTIME PERINATAL MORTALITY HAVE NOT BEEN EXCLUDED
Dear Editor
The unstated premise of the article by Heller et al1 that the incidence of
perinatal death due to intrapartum asphyxia in low risk pregnancies may
serve as a sensitive measure of the quality of peripartum care delivered
is appealing 2. However the proposition by Heller that the observed higher
nocturnal perinatal mortality in a selected population was a result of
substandard care was not justified in the article.
Firstly, a comprehensive index case record interrogation was absent.
The Confidential Enquiry in to Stillbirths and Deaths in Infancy (CESDI) 3
adopts the gold standard method of a multi-disciplinary scrutiny of the
records to ensure diagnostic accuracy as well as quantification of any
substandard care involved.
Secondly, imprecise selection criteria ensured the sample population
was heterogeneous in terms of pregnancy risk and method of delivery.
Further bias arose as Heller’s early neonatal death rate (0.15 per 1000
births selected) represented only a small fraction of the unstated overall
early neonatal death rate (3.1 per 1000 live births found in a similar
population by CESDI 2).
Thirdly, recommended criteria necessary before a diagnosis of acute
perinatal asphyxia can be made 4 were not adopted by Heller’s article.
Furthermore it is noteworthy that deaths classified as ‘asphyxia related’
occurring as a result of hypoxia during labour do not necessarily mean
that the hypoxia was preventable.
More useful information would have been derived if the crude early
neonatal death rate data were reclassified in a pathophysiological cause-
specific manner e.g. adopting the amended Wigglesworth classification 5 or
incorporated birth weight/gestation specific mortality. Such cause-
specific mortality relationships better identify the exact contribution of
antepartum and intrapartum risk factors to infant mortality and whether
there is any diurnal variation to their incidence. Importantly, Heller’s
article could not demonstrate whether high-risk pregnancies present more
frequently at night. Case-control analysis of matched cases with similar
obstetric-neonatal factors and delivery centres but differing by delivery
time could further reveal the contribution of delivery time to perinatal
death and whether this relationship is cause-specific.
Ultimately the identification of pregnancies without substandard care
or obstetric risk that still incur a significantly higher nocturnal
perinatal mortality pose a serious concern which perhaps represents a
manifestation of the maternal-fetal physiology specific to this period
which at present is unknown. Antepartum "unexplained" fetal death might
also enter into this subgroup, which, despite advances in obstetric
medicine and fetal monitoring, comprises the majority of perinatal deaths.
Standards of health care delivery are always under inspection (e.g.
Clinical Governance, the media) and thus comprehensive evaluation, with
consideration given to other possible causes, is essential before such
‘human’ issues are drawn into the causality equation for adverse outcome
occurring at night.
Yours sincerely
Rajesh Varma MA MRCOG DFFP
Senior SHO Obstetrics and Gynaecology
Srinivas Vindla MD MRCOG
Specialist Registrar Obstetrics and
Gynaecology
Lawrence Mascarenhas MD MRCOG M.Ed
Consultant Obstetrician and
Gynaecologist
Department of Obstetrics and Gynaecology, Queens Medical Centre,
Nottingham, NG7 2UH
E-mail DrRajesh@varma16.freeserve.co.uk
References
1. Heller G, Misselwitz B, Schmidt S. Early neonatal mortality, asphyxia
related deaths, and timing of low risk births in Hesse, Germany, 1990-98:
observational study. BMJ 2000; 321: 274-5
2. Field DJ, Smith H, Mason E, Milner AD. Is perinatal mortality still a
good indicator of perinatal care? Paediatr Perinat Epidemiol 1988; 2:213-9
3. Confidential Enquiry into Stillbirths and Deaths in Infancy. Sixth
Annual Report. London: Maternal and Child Health Research Consortium. 1999
4. American Academy of Pediatrics, American College of Obstetricians and
Gynecologists. Relationship between perinatal factors and neurologic
outcome. In: Poland RL, Freeman RK, editors. Guidelines for perinatal
care. 3rd ed. Elk Grove Village (IL): American Academy of Pediatrics;
1992.pp 221-4.
5. Keeling JW, MacGillivray I, Golding J, Wigglesworth J, Berry J, Dunn
PM. Classification of perinatal death. Arch Dis Child 1989; 64: 1345-1351
Competing interests: No competing interests