This study measures the plasma half-life of 25-hydroxyvitamin D3 (25(OH)D3) in non-pregnant-non-lactating women, pregnant women at 30 wk gestational age and at 3 months post-partum in women who are exclusively breast-feeding.

Inclusion Criteria:

All participants:

• Currently resident in West Kiang and planning to stay for the next 5 months
• Aged between 18 and 45 y

Pregnancy:

• > 20 wk < 30 wk pregnant (gestational age assessment by ultrasound)
• Singleton fetus

Lactation:

• Breast feeding

Exclusion Criteria:

All participants:

• Severe anaemia (haemoglobin < 7 g/dL) (as per ENID protocol)
• Known sickle cell anaemia
• Known to be asthmatic or allergic to peanuts (already excluded from ENID)
• Known history of liver, kidney, gut or malabsorption problems
• Other chronic condition
• On prescription medication
• Taking vitamin D supplements (> 200 IU/d)
• Broken bone in last 3 y
• Recent infection or illness (2 weeks prior to the start of a study period)
• Reported onset of menopause (already excluded from ENID)
• Malaria parasitemia (prior to study period)
• Unable to consent

Pregnant:

• Pregnancy-related complications or on discretion of mid-wife
• Known HIV positive

Lactation:

• Health problem of mother or infant that may affect feeding practices