From: 3.2 million stillbirths: epidemiology and overview of the evidence review
CONDITION OR RISK FACTOR | PROBABLE MECHANISMS |
---|---|
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) |