Vitamin D status and recurrent preterm birth: a nested case-control study in high-risk women.
OBJECTIVE
To determine whether vitamin D status is associated with recurrent preterm birth, and any interactions between vitamin D levels and fish consumption.


METHODS
A nested case-control study, using data from a randomised trial of omega-3 fatty acid supplementation to prevent recurrent preterm birth.


METHODS
Fourteen academic health centres in the USA.


METHODS
Women with prior spontaneous preterm birth.


METHODS
In 131 cases (preterm delivery at <35 weeks of gestation) and 134 term controls, we measured serum 25-hydroxyvitamin D [25(OH)D] concentrations by liquid chromatography-tandem mass spectrometry (LC-MS) from samples collected at baseline (16-22 weeks of gestation). Logistic regression models controlled for study centre, maternal age, race/ethnicity, number of prior preterm deliveries, smoking status, body mass index, and treatment.


METHODS
Recurrent preterm birth at <37 and <32 weeks of gestation.


RESULTS
The median mid-gestation serum 25(OH)D concentration was 67 nmol/l, and 27% had concentrations of <50 nmol/l. Serum 25(OH)D concentration was not significantly associated with preterm birth (OR 1.33; 95% CI 0.48-3.70 for lowest versus highest quartiles). Likewise, comparing women with 25(OH)D concentrations of 50 nmol/l, or higher, with those with <50 nmol/l generated an odds ratio of 0.80 (95% CI 0.38-1.69). Contrary to our expectation, a negative correlation was observed between fish consumption and serum 25(OH)D concentration (-0.18, P < 0.01).


CONCLUSIONS
In a cohort of women with a prior preterm birth, vitamin D status at mid-pregnancy was not associated with recurrent preterm birth.
Department of Obstetrics and Gynecology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7570, USA. thorp@med.unc.edu
J M
JM
Thorp
C A
CA
Camargo
P L
PL
McGee
M
M
Harper
M A
MA
Klebanoff
Y
Y
Sorokin
M W
MW
Varner
R J
RJ
Wapner
S N
SN
Caritis
J D
JD
Iams
M W
MW
Carpenter
A M
AM
Peaceman
B M
BM
Mercer
A
A
Sciscione
D J
DJ
Rouse
S M
SM
Ramin
G B
GB
Anderson
D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D002853:Chromatography, Liquid; D004032:Diet; D004034:Diet Surveys; D005260:Female; D006801:Humans; D016015:Logistic Models; D013058:Mass Spectrometry; D011247:Pregnancy; D047928:Premature Birth / Q000097:blood / Q000209:etiology*; D039401:Prenatal Nutritional Physiological Phenomena; D011446:Prospective Studies; D012008:Recurrence; D012306:Risk; D017747:Seafood; D057566:Self Report; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D