The Vitamin D and fetal bone length study:

Vitamin D and its association to bone length in midterm pregnancy.

Overall:

The Odense Child Cohort Study (OCC) is a population-based cohort study, comprising pregnant women recruited between January 1st 2010 and December 31st 2012. All women who were pregnant in the municipality of Odense during this time were eligible for participation, and 6,707 women were approached directly with recruitment material.

The study complied with the Helsinki declaration and was approved by the Regional Scientific Ethical Committee for Southern Denmark, no. S-20090130. All participants gave informed consent. From a population base of 6,707 pregnant women, 2,874 (42.9%) enrolled in the OCC up to December 31st, 2012. The children will be followed until 18 years of age.

Serum samples were taken in early pregnancy (GA 2-25 weeks), late pregnancy (GA 26-30 weeks), maternal serum and cord blood at birth, and from the children along with general examinations at ages 3 months, 1 year, 3 years.

Questionnaires were completed by the families in early pregnancy, late pregnancy, after birth, and at the times of clinical examination of the children.

Register data on health variables were further available from the Danish registries.

Objective:

The Vitamin D and bone length Study examines the relationship between the biomarker 25(OH)D in maternal serum and the length of the fetal femur and humerus bone at mid term pregnancy.

Method:

25(OH)D analysis: Serum was stored at -80º Celsius until analysis, which was performed by liquid chromatography mass spectrometry (LC-MS/MS). Triple deuterium marked 25(OH)vitamin D3 was added to serum samples as internal standard and deproteinized with ZnSO4 in methanol, centrifuged at 2750 g for 10 minutes, and 100 μl was injected on the TurboFlow column (Thermo Scientific) on the LC-MS/MS. The LC-MS/MS consisted of a Thermo Scientific TLX1 system connected to a Thermo Scientific Vantage TSQ. 25(OH)D2 and 25(OH)D3 were concentrated on a Thermo Scientific Cyclone P 50 x 1.0 mm column and back-flushed on the analytical column, Phenomenex Gemini C18 50 x 3.0 mm and eluted from the analytical column by a gradient. Mobile phases were A: 10 mM NH4Ac in water and B: 10 mM NH4Ac in methanol. Human serum was spiked with appropriate amounts of 25(OH)D2 and 25(OH)D3 in order to produce six point calibration curves (weighed 1/x2) and 3 levels of QC samples (low, mid, high). The method was calibrated against NIST standard 972.25 The C3 epimer of D3 was detected along with D3 and the two were not distinguishable from one another. Lowest detectable concentrations were 0.15 nM for both D2 and D3. Values of D2 and D3 were only considered if above 6.5 nM.

The Vitamin D and bone length study:

Vitamin D and bone length in mid term pregnancy.

- In 986 serum samples collected in early pregnancy, the levels of serum 25(OH)D were investigated by LC-MS/. Questionnaire and medical file information was used to determine the factors which were influential on 25(OH)D levels and bone length in mid term pregnancy by multiple linear regression.

Inclusion Criteria:

• Pregnant and residing in the municipality of Odense during 2010-2012

Exclusion Criteria:

• Not residing in Odense, leaving the municipality

The Odense Child Cohort Study (OCC) is a population-based cohort study, comprising pregnant women recruited between January 1st 2010 and December 31st 2012. All women who were pregnant in the municipality of Odense during this time were eligible for participation, and 6,707 women were approached directly with recruitment material.

The study complied with the Helsinki declaration and was approved by the Regional Scientific Ethical Committee for Southern Denmark, no. S-20090130. All participants gave informed consent. From a population base of 6,70 pregnant women, 2,874 (42.9%) enrolled in the OCC up to December 31st, 2012. The children will be followed until 18 years of age.