Table 1

Criteria used to define cases of severe maternal morbidity used in the UKOSS studies included in the analysis

ConditionDefinitionUKOSS study timeframe
Amniotic fluid embolismEITHER a clinical diagnosis of AFE (acute hypotension or cardiac arrest, acute hypoxia or coagulopathy in the absence of any other potential explanation for the symptoms and signs observed)
OR a pathological diagnosis (presence of fetal squames or hair in the lungs)
Acute fatty liver of pregnancyEITHER AFLP confirmed by biopsy or postmortem examination
OR a clinician has made a diagnosis of AFLP with signs and symptoms consistent with AFLP
EclampsiaThe occurrence of convulsions during pregnancy or in the first 10 days postpartum, together with at least two of the following features within 24 h after the convulsions:
(1) Hypertension (a booking diastolic pressure of <90 mm Hg, a maximum diastolic of ≥90 mm Hg and a diastolic increment of ≥25 mm Hg)
(2) Proteinuria (at least+protein in a random urine sample or ≥0.3 g in a 24 h collection)
(3) Thrombocytopenia (platelet count of <100×109/L)
(4) An increased plasma alanine aminotransferase (ALT) concentration (≥42 IU/L) or an increased plasma aspartate transaminase aminotransferase (AST) concentration (≥42 IU/L)
Peripartum hysterectomyAny woman giving birth to an infant and having a hysterectomy during the same clinical episode01/02/2005–29/02/2006
Therapies for major peripartum haemorrhageAll women in the UK treated therapeutically or prophylactically for major peripartum haemorrhage with:
EITHER Activated factor VIIa
OR B-lynch suture or other brace suture
OR Arterial ligation or embolisation
Uterine ruptureAny woman in the UK identified as having a uterine rupture using the following definition:
A complete separation of the wall of the pregnant uterus, with or without expulsion of the fetus, involving rupture of the membranes at the site of the uterine rupture or extension into the uterine muscle separate from any previous scar, and endangering the life of the mother or fetus
Excluded: any asymptomatic palpable or visualised defect (eg,dehiscence noted incidentally at caesarean delivery)
  • AFE, amniotic fluid embolism; AFLP, acute fatty liver of pregnancy; UKOSS, UK Obstetric Surveillance System.