Systematic review of first-trimester vitamin D normative levels and outcomes of pregnancy.
Am J Obstet Gynecol. 2011 Apr 7.
Nassar N (natasha.nassar@uwa.edu), Halligan GH, Roberts CL, Morris JM, Ashton AW.
Perinatal Research, Kolling Institute of Medical Research, University of Sydney, NSW, Australia.
OBJECTIVE:
We undertook a systematic review to assess normative levels of vitamin D in early pregnancy and association with subsequent pregnancy outcomes.
STUDY DESIGN:
Medline and Embase databases and reference lists were searched. Inclusion criteria were pregnant populations, blood sample taken during the first trimester, and serum hydroxyvitamin D levels assessed.
RESULTS:
Eighteen studies reported vitamin D levels in first trimester (n = 11-3730), and 5 examined pregnancy outcomes.
Mean vitamin D concentrations differed when stratified by ethnicity:
- white (mean {SD}: 29.4 {11.7 } to 73.1 {27.1} nmol/L) and
- non-white (15.2 {12.1} to 43 {12} nmol/L).
Most studies used general population cut points to define deficiency and found a large proportion of women deficient.
Two articles examined risk of preeclampsia and reported differing findings, whereas 2 of 3 found low levels associated with increased risk of small-for-gestational age births.
CONCLUSION:
There is no clear definition of vitamin D deficiency in pregnancy and insufficient evidence to suggest low vitamin D levels in early pregnancy are associated with adverse pregnancy outcomes.
PMID: 21640968
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This conflicts with the rest of the studies
Their conversions for vitamin D appear to have an error
White 29.4 nmol does equal 12 ng/ml
Non-white 15.2 nmol does NOT equal 12.1ng/ml, but does equal 6 ng/ml