Bulletin of the World Health Organization

Applying the international classification of diseases to perinatal mortality data, South Africa

Tina Lavin a, Emma R Allanson b, Lee Nedkoff c, David B Preen a & Robert C Pattinson d

a. Centre for Health Services Research, School of Population and Global Health, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth, Australia.
b. School of Women’s and Infants’ Health, The University of Western Australia, Perth, Australia.
c. Cardiovascular Research Group, School of Population and Global Health, The University of Western Australia, Perth, Australia.
d. Maternal and Infant Health Care Strategies Unit, University of Pretoria, Pretoria, South Africa.

Correspondence to Tina Lavin (email: tina.lavin@uwa.edu.au).

(Submitted: 05 December 2017 – Revised version received: 13 June 2018 – Accepted: 02 August 2018 – Published online: 17 October 2018.)

Bulletin of the World Health Organization 2018;96:806-816. doi: http://dx.doi.org/10.2471/BLT.17.206631

Introduction

High on the global health agenda is the need to accelerate progress towards ending preventable perinatal deaths, defined by the World Health Organization (WHO) as either a stillbirth of weight > 1000 g or after at least 28 weeks gestation, or an early neonatal death in the first 7 days after birth.1 In developing appropriate intervention strategies to reach this target, the causes of perinatal deaths must be classified in a globally comparable way.2,3 A recent systematic review identified no less than 81 different systems used to classify perinatal deaths globally, with only 17 systems using the International Statistical Classification of Diseases and Related Health Problems (ICD) codes.4 Other studies have recognized that multiple, disparate systems impede the ability to understand and achieve accurate estimates of cause of death, hindering effective prevention strategies.5,6 Of particular importance is the need to focus on the mother–infant dyad, as maternal condition is closely related to perinatal death.1

The Every Newborn Action Plan recommends that maternal complications be recorded as part of perinatal death registration; however, challenges existed in applying the 10th edition of the ICD (ICD-10) classification system as maternal condition was not linked to perinatal condition.7 To address these issues, the WHO application of ICD-10 to perinatal deaths (ICD-perinatal mortality or ICD-PM) was published in 2016,8,9 the first perinatal death classification system developed for application globally.10 ICD-PM is modelled on the WHO application of the ICD-10 system to deaths during pregnancy, childbirth and the puerperium (ICD-maternal mortality or ICD-MM),11 and follows all coding rules of ICD-10.12 Importantly, the ICD-PM system identifies the timing of perinatal death (i.e. antepartum, intrapartum or neonatal), links causes of death to existing ICD-10 codes and connects maternal condition with perinatal death.8 One of the aims of ICD-PM is to group ICD-10 codes into clinically relevant and easy-to-use categories.10

We demonstrate the benefits achieved, in terms of an improved understanding of the data, from the application of ICD-PM codes to perinatal deaths that were previously classified using the South African perinatal mortality audit system, called Perinatal Problem Identification Program.

Methods

Data source

South Africa’s perinatal mortality audit system13 records and classifies perinatal deaths at all 588 clinics across the country. Each clinical team performs a mortality review shortly after death and reports the cause of perinatal death (and associated maternal condition) to the classification system. For the purposes of the system, perinatal deaths are defined as either fresh or macerated stillbirth or early neonatal death (age 0–7 days). The primary obstetric cause of death is classified in terms of both lead categories and subcategories according to Box 1. Maternal condition is also recorded, and classified as either healthy (where the examining clinician did not identify any clinical problems) or as one of the medical/obstetric conditions listed in Box 2. Classifications of perinatal death are linked to maternal condition lead categories, but not to subcategories. Data are joined into a national database at the Medical Research Council Unit for Maternal and Infant Health Care Strategies, Pretoria. Regular auditing of individual clinics is conducted to ensure the completeness and accuracy of the database.

Box 1. South African Perinatal Problem Identification Program classification of primary cause of perinatal death

Intrauterine death

Subcategories: unexplained intrauterine death (macerated); unexplained intrauterine death (fresh); and unexplained intrauterine death (due to lack of notes)

Intrapartum asphyxia

Subcategories: Labour-related intrapartum asphyxia; meconium aspiration; cord around the neck; cord prolapsed; ruptured uterus; traumatic breech delivery; shoulder dystocia; precipitous labour; and traumatic assisted delivery

Hypertensive disorders

Subcategories: proteinuric hypertension; eclampsia; pregnancy-induced hypertension without proteinuria; and chronic hypertension

Antepartum haemorrhage

Subcategories: abruptio placentae; abruptio placentae with hypertension; antepartum haemorrhage of unknown origin; and placenta praevia

Spontaneous preterm labour

Subcategories: idiopathic preterm labour; premature rupture of membranes; iatrogenic preterm delivery for no real reason; premature rupture of membranes with chorioamnionitis; preterm labour with chorioamnionitis with intact membranes; and cervical incompetence

Fetal abnormality

Subcategories: fetal chromosomal abnormality; abnormality of multiple systems; neural tube defects; hydrocephalus; non-specific fetal abnormality; cardiovascular system abnormality; non-immune hydrops fetalis; and renal system abnormality

Infections

Subcategories: other infections; amniotic fluid infection; syphilis; β-haemolytic streptococcal infection; and malaria

Intrauterine growth restriction

Subcategories: idiopathic intrauterine growth restriction; postmaturity; and with histological features of ischaemic placental disease

No obstetric cause

Maternal disease

Subcategories: maternal diabetes mellitus; other maternal disease; maternal disease due to herbal medicine use; and maternal heart disease

Miscellaneous

Subcategories: other cause of death not described in classification; twin-to-twin transfusion; rhesus isoimmunization; and extrauterine pregnancy

Trauma

Subcategories: motor vehicle accident; accidental abdominal trauma; assault; and domestic violence

Box 2. South African Perinatal Problem Identification Program classification of maternal conditions

No obstetric condition

Subcategory: healthy mother

Coincidental conditions

Subcategories: herbal medicine; other coincidental conditions; other accidents; motor vehicle accident; assault; and rape

Medical and surgical disorders

Subcategories: endocrine disease; other medical and surgical disorders; autoimmune disease; haematological disease; genitourinary disease; cardiac disease; respiratory disease; central nervous system disease; psychiatric disease; gastrointestinal disease; neoplastic disease; and skeletal disease

Non-pregnancy-related infections

Subcategories: urinary tract infection; other non-pregnancy-related infections; tuberculosis; complications of antiretroviral therapy; wasting syndrome; other pneumonia; pneumocystis pneumonia; malaria; gastroenteritis; other meningitis; cryptococcal meningitis; hepatitis; Kaposi sarcoma; appendicitis; endocarditis; and toxoplasmosis

Pregnancy-related sepsis

Subcategories: chorioamnionitis with ruptured membranes; and chorioamnionitis with intact membranes

Obstetric haemorrhage

Subcategories: abruption with hypertension; abruption without hypertension; other acute postoperative hypertension (not specified); placenta praevia; ruptured uterus with previous caesarean section; and ruptured uterus without previous caesarean section

Hypertension

Subcategories: Proteinuric hypertension; pregnancy-induced hypertension without proteinuria; eclampsia; chronic hypertension; haemolysis, elevated liver enzymes and low platelet count (HELLP syndrome); liver rupture; and acute fatty liver

Acute collapse (cause unknown)

Anaesthetic complications

Subcategories: complications of general anaesthetic; complications of spinal anaesthetic; complications of epidural anaesthetic

Extrauterine pregnancy

Embolism

Subcategories: amniotic fluid embolism; and pulmonary embolism

Note: Only lead categories and not subcategories can be linked to perinatal deaths.

We used all 26 810 perinatal deaths, which occurred during the period between 1 October 2013 and 31 December 2016, recorded in the classification system’s database (Table 1). The start date coincided with the launch of the third version of the system, which had been improved to include gestational age at death.

Conversion to ICD-PM coding

The first author, a non-clinical researcher with a background in public health, studied The WHO application of ICD-10 to deaths during the perinatal period: ICD-PM9 to learn to apply ICD-PM codes to the classification system’s database. The coding conversion took place between November 2017 and January 2018. The second author, a consulting obstetrician, provided guidance and verification on a voluntary basis. The ICD-PM system2,9,14 classifies mortality according to: (i) time of death, whether antepartum (A1–A6), intrapartum (I1–I7) or neonatal (N1–N11); (ii) the primary cause of perinatal death (e.g. loss of fetal blood: P50); and (iii) the main maternal condition (M1–M4 to describe various complications and conditions, and M5 for healthy mother) at the time of perinatal death.

Ethics

Data were collected with the permission of the South African Department of Health. This analysis was approved by the technical task team who run the database and produce the reports from the South African Medical Research Council/University of Pretoria Maternal and Infant Health Care Strategies unit. This was a secondary analysis and all identifiers of the cases were removed. Ethics approval was given by the University of Western Australia Human Ethics Committee (RA/4/1/7955, 20 November 2015).

Results

Table 2 shows the reclassification of perinatal deaths using the ICD-PM and the primary causes of death are linked to maternal condition. Most deaths were antepartum in timing (15 619/26 810; 58.3%), followed by neonatal (7466/26 810; 27.8%) and intrapartum (3725/26 810; 13.9%). Of the total number of perinatal deaths, 8.8% (2368) were associated with a maternal death.

Antepartum deaths

Antepartum deaths were largely due to fetal deaths of an unspecified cause (10 542 deaths; 67.5%; ICD-PM code A6), other specified antepartum disorder (2947 deaths; 18.9%; A4) or disorders related to fetal growth (1270 deaths; 8.1%; A5; Table 2). Of the 15 619 antepartum deaths recorded, 41.0% (6411) of the mothers had no maternal condition. For most of antepartum deaths classified as fetal death of unspecified cause, the mothers were free from any maternal complication (53.9%; 5678/10 542; A6 M5): 5537 (97.5%) deaths were due to an unexplained intrauterine death (A6 P95), 56 deaths (1.0%) were described as miscellaneous or other causes not described by the South African classification (A6 P95), and 85 (1.5%) deaths had no obstetric cause (M5).

Antepartum deaths classified as other specified antepartum disorder (2947 deaths; 18.9%; A4) were further classified under fetal blood loss (2342 deaths; P50), with the main causes being abruptio placentae (1124 deaths; 38.1%; A4 P50 M1 P02.1), abruptio placentae with hypertension (928 deaths; 31.5%; A4 P50 M1 P02.1), antepartum haemorrhage of unknown origin (106 deaths; 3.6%; A4 P50 M1 P02.1), placenta praevia (69 deaths; 2.3%; A4 P50 M1 P02.0) and twin-to-twin transfusion (115 deaths; 3.9%; A4 P50 M1 P02.3). Where fetal blood loss was the primary cause of perinatal death, 595 deaths were related to maternal medical and surgical conditions (M4), including: hypertension (406 deaths), medical and surgical complications (114 deaths), non-pregnancy-related infections (21 deaths), coincidental (14 deaths), sepsis (4 deaths), anaesthetic (4 deaths) and acute collapse (3 deaths), all coded as A4 P50 M4; and rhesus isoimmunization (29 deaths), coded as A4 P55.0 M4 P00.9. There were 10 antepartum haemorrhages with ectopic pregnancies, coded as A4 P50 M2 P01.4. Causes of death relating to haemorrhage described by code P52 are not categorized in the South African database, so we could not utilize this code during our conversion.

Intrapartum deaths

The main causes of the 3725 intrapartum deaths (Table 2) were acute intrapartum event (2576 deaths; 69.2%; I3), other specified intrapartum disorder (479 deaths; 12.9%; I5) or intrapartum death of unspecified cause (373 deaths; 10.0%; I7). The other 297 deaths were classified as congenital malformations, deformations and chromosomal abnormalities (190 deaths; 5.1%; I1), infection (43 deaths; 1.7%; I4) and disorders related to fetal growth (64 deaths; 1.7%; I6). All deaths due to acute intrapartum events were classified as I3 P20.10 intrauterine hypoxia, first noted during labour and delivery. Of the intrapartum deaths of unspecified cause, most were due to hypertensive disorders (269 deaths; 72.1%) or maternal disease (46 deaths; 12.3%). Of all the intrapartum deaths; 11.0% (411 deaths) were not associated with any maternal complication.

Neonatal deaths

The main causes of the 7466 neonatal deaths were complications of intrapartum events (2184 deaths; 29.3%; N4) or low birth weight and prematurity (2128 deaths; 28.5%; N9). All neonatal deaths classified as complications of intrapartum events were due to severe birth asphyxia (N4 P21; Table 2). Of all neonatal deaths, 1521 (20.4%) were not associated with any maternal complication. A large proportion (3118 deaths; 41.8%) of neonatal deaths were attributed to other complications of labour and delivery (M3). Of those deaths coded as M3, 1550 (49.7%) were due to labour-related intrapartum asphyxia (P03.9), 1456 (46.7%) were due to idiopathic preterm labour (P03.8 O60.0), 31 (1.0%) occurred as a result of traumatic breech delivery (P03.0), 25 (0.8%) were due to a precipitous labour (P03.5), 25 (0.8%) resulted from shoulder dystocia (P03.8 O66.0), 19 (0.6%) were due to traumatic assisted delivery (P03.2, P03.3) and 12 (0.4%) were due to a ruptured uterus (P03.8 O71.1).

Table 3 provides an example of how ICD-PM codes were applied to neonatal deaths classified by the South African classification system as being due to preterm labour. According to the classification system, most (83.5%, 1772/2121) of the deaths due to preterm labour were associated with a healthy maternal condition. Under the ICD-PM classification, however, 96.5% of these (1710/1772) were associated with a non-healthy maternal condition. For example, cases of perinatal death due to idiopathic preterm labour, premature rupture of membranes, premature rupture of membranes with chorioamnionitis, cervical incompetence and premature rupture of membranes with chorioamnionitis and intact membranes were assigned the codes M3 P03.8, M2 P01.1, M2 P01.1, M2 P01.0 and M1 P02.7, respectively. Only 3.5% (62/1772; iatrogenic preterm delivery for no real reason) of neonatal deaths due to preterm labour associated with a healthy mother, according to the South African classification, are coded as M5 under the ICD-PM system.

Discussion

Here we show that ICD-PM coding improve consideration of maternal complication when classifying perinatal deaths. Previous research in South Africa reported that maternal complications were linked to around one half of all stillbirths and one quarter of early neonatal deaths. 13 According to the South African classification system, 45.7% (8644/18 927) of stillbirths and 27.4% (2158/7883) of early neonatal deaths were classified as being linked to a maternal complication; this is equivalent to 40.3% (10 802/26 810) of all deaths. In contrast, our analysis of ICD-PM classifications identified a much higher proportion of maternal conditions for these outcomes. Maternal complications were associated with 59.0% (9208/15 619) of antepartum deaths, 89.0% of (3314/3725) intrapartum deaths and 79.6% (5945/7466) of neonatal deaths; this is equivalent to 68.9% (18 467/26 810) of all deaths.

We managed to classify all neonatal deaths with a primary cause of intrapartum asphyxia with an associated maternal condition using the ICD-PM codes, while the South African classification system only classified 17.4% (512/2942). Several subcategories such as labour-related intrapartum asphyxia, cord around the neck and others as outlined in Box 1 are classified according to the South African classification system as perinatal complications with a healthy mother. Using the ICD-PM system, however, these deaths can be correctly categorized as the result of a maternal condition. Antepartum haemorrhage, because of abruptio placentae or placenta praevia is considered a perinatal condition under the South African classification system, but classified as a maternal condition by the ICD-PM system.

We also show that ICD-PM coding improve consideration of timing of death. A recent systematic review found that 59% of globally reported stillbirths had no information regarding the timing of death,15 making the appropriate timing of interventions difficult to identify. Further, in some resource-poor settings the timing of a perinatal death may be the only piece of information captured. This information should therefore be a part of any classification system.16

The application of the ICD-PM coding system to our data revealed a significant burden of deaths occurring during the antepartum period. Further, more than a quarter of early neonatal deaths were due to low birth weight. This highlights the already established importance of investment in antenatal care to reduce perinatal mortality. The 2016 WHO antenatal care recommendations17 include an increased number of antenatal care contacts in the third trimester. In response to these recommendations and the increased number of third-trimester stillbirths observed when antenatal care visits had not been made during this period, the number of recommended antenatal care visits was changed in South Africa in April 2017.18

A commonly cited burden of perinatal mortality is prematurity and prematurity-related causes.19 However, simply identifying that prematurity is an important contributor to deaths gives no information regarding the optimal timing for interventions. From the ICD-PM classification, we see that 36.7% (1270; coded under A5, disorders related to fetal growth) of deaths due to prematurity (3426; the total of deaths classified as A5, I6 or N9) occurred during the antepartum period, and that 72.7% (923/1270) of these deaths were also related to a maternal complication. This information is invaluable to public health workers and policy-makers in targeting interventions; a heightened awareness of the causes of such deaths allows a focus on preterm-related issues, showing that both obstetric and neonatal interventions are required.

For implementing ICD-PM coding, systematic training of data administrators in the classification of deaths using ICD-PM will be required to ensure familiarity with the new system, as well as consistency across settings. Data administrators will also need to have access to clinicians to discuss cases that do not clearly fit a specific ICD-PM classification. In our experience, however, the ICD-PM system is both clinically relevant and easy to use; for example, the coder for this study does not have a clinical background. There was a high level of agreement between the coder and the verifying obstetrician, with differences encountered in only two cases: (i) premature rupture of membranes with chorioamnionitis (M1 P01.1 according to coder, M1 P02.7 according to obstetrician) and (ii) unexplained uterine death (A3 according to coder, A6 according to obstetrician). This demonstrates the feasibility in implementing the ICD-PM codes to existing data sets by administrators or allied health providers, in consultation with clinicians. Data administrators can be trained in the application of ICD-PM coding under the mentorship of clinicians, an advantage in low-resource settings.

We noted some specific issues with ICD-PM, including mutually exclusive categories, deaths which could be classified under two different ICD-PM codes, multiple contributing factors for cause of death, and causes of death not captured by the South African classification system but considered by ICD-PM codes (or vice versa). Examples of these issues and potential solutions are discussed in Table 4.

As maternal and perinatal outcomes are closely related, both mother and infant benefit from intervention;2 this is particularly relevant in the management of hypertension and care during the intrapartum period.3,20,21 However, possible challenges exist with the application of the ICD-PM system to data sets which consider perinatal death and maternal condition separately, introducing issues in the integration of the two systems. The adaption of integrated perinatal and maternal data collection systems may be difficult in poorly resourced settings. For countries that do not have well established death classification systems, future developments could consider autopsy review categories aligned with ICD-PM codes for better consistency between death review and coding stages. For example, the South African classification system could be strengthened to align more closely to ICD-PM as described in Table 4.

In conclusion, by allowing for an increased recognition of the role of maternal condition and the timing of death in perinatal mortality, our conversion of an existing national perinatal mortality data set to ICD-PM codes enhanced our understanding of the data. This work is part of a larger work investigating perinatal deaths in South Africa and the required interventions.18,22 Our new classification of perinatal deaths could inform the allocation of resources and the timing of interventions. Adopting the ICD-PM coding system internationally would lead to a consistent global perinatal death classification system, which would create comparable data that could inform policy-makers globally.


Competing interests:

None declared.

References