Table 2 Mechanisms for stillbirth and the linked conditions and risk factors

Maternal age at pregnancy or birth spacing practices

   • Pregnancy at young age (<18 yrs)

• Increased risk of obstetric complications e.g. obstructed labour if young (<18)

   • Maternal age > 35

• Increased risk of pregnancy induced hypertension in teenage pregnancies

   • Short interpregnancy interval

• Increased risk of congenital anomalies, particularly chromosomal defects, with advanced maternal age

   • Grand multiparity (> 4 prior pregnancies)

• Increased risk of gestational diabetes with grand multiparity

Maternal nutritional status before pregnancy:

   • Short maternal stature (<145 cm)

• Increased risk of feto-pelvic disproportion if malnourished in childhood

   • Undernutrition (low BMI/specific Micronutrient deficiencies (eg folate)

• Increased risk of neural tube defects with folic acid deficiency

   • Obesity

• Unknown pathways (e.g., obesity carries risk of gestational diabetes and pre-eclampsia, but mechanisms unknown)

   • Severe anaemia

Maternal medical conditions during pregnancy:

   • Diabetes

• Uncontrolled diabetes may result in macrosomia and increased risk of obstructed labour

   • Hypertensive disorders (pre-eclampsia/eclampsia)

• Poorly controlled diabetes carries increased risk of congenital abnormalities

   • Cholestasis or other liver disease

• Placental dysfunction including abruption (hypertension), reduced fetal growth, increased risk of acute on chronic fetal hypoxia

   • Thrombophilias

• Placental abnormalities like intravascular thrombi, decidual vasculopathy and ischemic necrosis with villous infarctions (in thrombophilias)

Exposure to harmful substances:

   • Tobacco/alcohol/drug use

• Reduced fetal growth, increased risk of acute on chronic fetal hypoxia (increased fetal carboxyhemoglobin and vascular resistance with smoking and biomass fuels)

   • Cooking fires (biomass fuel)

• Increased risk of congenital abnormalities with exposure to certain toxins or drugs, including occupational exposure such as pesticides

   • Exposure to environmental toxins

Contextual factors: socioeconomic disadvantage and access to care, especially obstetric care:

   • Poor access to healthcare services because of distance, and/or financial barriers

• Increased risk of obstetric complications e.g. obstructed labour if young (<18) and/or malnourished in childhood and/or FGM resulting in increased combined risk of feto-pelvic disproportion

   • Ethnic or religious minority affecting equal access to care

• Increased risk of infection and undiagnosed/untreated infections

   • Maternal illiteracy/low educational status

• Increased delays in accessing care

   • Female genital mutilation (FGM)

• Lack of quality emergency obstetric care even when care is accessed (e.g. no caesarean section or delay to time of section, or need for additional payments)

• Inability to afford quality obstetric care

• Some risk factors are systematically associated with low socio-economic status (e.g., extremes of maternal age, extremes of body mass index, and smoking, alcohol and drug abuse)