General anaesthesia for Caesarean Section

Every woman of over 24 weeks of gestation given a general anaesthetic for a Caesarean section.


Re-exploration after Caesarean Section

Any woman who has a Caesarean Section (CS) AND who returns to theatre AND


An exploration of the CS wound with the rectus sheath (RS) re-opened (i.e. deep exploration of the wound because of a wound problem, requiring the rectus sheath to be opened)


a formal laparotomy (opening of the peritoneum) (e.g. to control bleeding, deal with abdominal/ pelvic infection, undertake a hysterectomy or for any other reason)

within 28 days of CS


Intrahepatic Cholestasis of Pregnancy

Every pregnant woman identified as having intermediate (bile acids 40-99mcmol/L) or severe (bile acids ≥ 100mcmol/L) intrahepatic cholestasis of pregnancy, defined as:

  • Pruritus without rash associated with elevated serum bile acid levels >= 40 mcmol/L
  • At any stage of the pregnancy,
  • Not explained by other pathologies,
  • Disappearing after the delivery.

Exclusion criteria:

  • Serum bile acid levels less than 40mcmol/L
  • Other hepatic/infectious/dermatologic/pregnancy disease, which could explain the symptoms


Surgical Complications in Pregnancy of Bariatric Surgery

Every pregnant woman identified with bariatric surgery prior to conception presenting with a surgical complication diagnosed as

  • Internal herniation
  • Intussusception
  • Volvulus
  • Anastomotic stricture
  • Anastomotic or gastric ulcer
  • Ventral incisional hernia
  • Gastric band erosion
  • Gastric band slippage


COVID-19 in Pregnancy

Any pregnant woman or postpartum up till 42 days after the end of pregnancy

  • with diagnosis of COVID-19 infection
  • admitted to hospital
  • on or after 1st March 2020 and before 1st March 2021


Antenatal Pulmonary Embolism 

B.OSS will use the same definition as used by UKOSS, to enable comparison and participation in international studies.


PE is confirmed using suitable imaging (angiography, computed tomography, echocardiography, magnetic resonance imaging or ventilation-perfusion scan showing a  high probability of PE)

  • OR      PE is confirmed at surgery or postmortem
  • OR      a clinician has made a diagnosis of PE with signs and symptoms consistent with PE present, and the patient has received a course of anticoagulation therapy (>1 week duration)



defined according to UKOSS as

any woman with convulsion(s) during pregnancy or within the first 10 days after delivery, in combination with at least 2 of the following features within 24 hours of the convulsion(s) :

  • Hypertension : a maximum diastolic Blood Pressure of >= 90 mmHg and a diastolic increment of >= 25 mmHg (having had a diastolic Blood Pressure <90 mmHg at the first antenatal visit)
  • Proteinuria : at least + protein in a random urine sample or >= 0.3 g of proteins in a 24-hour collection
  • Thrombocytopenia : platelet count < 100000/ml
  • Raised transaminase levels : ALT of >= 42 IU/l or AST of >= 42 IU/l


Uterine rupture

Uterine rupture a larger definition is used including all uterine rupture cases as defined by UKOSS, but also to consider all other forms of uterine rupture as defined by the LEMMoN study in the Netherlands.

Uterine rupture as defined by UKOSS (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 uterine muscle separate from any previous scar, and endangering the life of the mother or the fetus),

Uterine rupture as defined by the LEMMoN study in the Netherlands (the occurrence of clinical symptoms (abdominal pain, abnormal fetal heart rate pattern, acute loss of contractions, vaginal blood loss), leading to an emergency caesarean delivery, at which the presumed diagnosis of uterine rupture was confirmed; or peripartum hysterectomy of laparotomy for uterine rupture after vaginal birth

UKOSS and LEMMoN both excluded any asymptomatic palpable or visualized defect (for example dehiscence) noted incidentally at caesarean delivery.


Postpartum Hysterectomy and embolisation of the uterine arteries

Postpartum Hysterectomy and embolisation of the uterine arteries as defined by UKOSS: being any woman giving birth to a fetus or infant and undergoing a hysterectomy in the same clinical episode. Similarly “peripartum embolization of the uterine arteries” will be considered when occurring in the same clinical episode.


Spontaneous hemoperitoneum in pregnancy (SHiP)

Key points:

  • SHiP is the occurence of sudden hemorrhage intraabdominally in pregnancy – unrelated to trauma or rupture of the uterus
  • SHiP has been associated with endometriosis, rupture of uterine artery or varicose veins and aneurysms of the splenic artery.
  • SHiP is rare but potentially fatal for the mother and the fetus.

Inclusion criteria: Any pregnancy after 22 weeks with sudden intraabdominal hemorrhage requiring surgery (CS, laparotomy, laparoscopy) - without preceding trauma.

Excluding: uterine rupture, trauma.


Anaphylaxis in Pregnancy

The cases will be all pregnant women (during pregnancy and up to 48 hours post delivery) identified as having anaphylaxis according to the following definition (Resuscitation Council, 2008).

Anaphylaxis is defined as a severe, life-threatening generalised or systemic hypersensitivity reaction. The following two criteria must be met for a diagnosis of anaphylaxis to be made:

1. A life-threatening airway problem and/or breathing problem and/or circulatory problem

2. Sudden onset and rapid progression of symptoms

1. A life-threatening airway problem is taken to include:

  • Laryngeal or pharyngeal oedema
  • Hoarse voice
  • Stridor

2. A life-threatening breathing problem is taken to include:

  • Shortness of breath and raised respiratory rate (or dyspnea)
  • Wheeze (laryngospasm or bronchospasm)
  • Decreased oxygen saturations
  • Confusion secondary to hypoxia
  • Cyanosis
  • Respiratory exhaustion or respiratory arrest

3. A life-threatening circulatory problem is taken to include:

  • Signs of shock such as faintness, pallor or clammy skin
  • Tachycardia >100bpm
  • Systolic BP <90mmHg or MBP<60mmHg or measured hypotension
  • Decreasing level of consciousness
  • Signs of ischaemia on ECG
  • Cardiac arrest

Previous definitions have included skin and/or mucosal features as a core criteria. However, these may not be evident if treatment is rapidly implemented, so this study shall include all women in whom the final clinical diagnosis is anaphylaxis, irrespective of the presence or absence of skin/mucosal changes.