On 2015 Feb 23, William Grant commented:

Vitamin D disparities may explain some of the findings regarding risk of primary cesarean delivery

The paper by Min and colleagues found many interesting results regarding correlations with primary cesarean delivery [1]. However, one additional important factor was overlooked: 25-hydroxyvitamin D [25(OH)D] concentration. This comment briefly summarizes how 25(OH)D concentrations are related to the findings of Ref. 1.

First, 25(OH)D concentrations have been found inversely correlated with primary cesarean delivery [2]. Second, black Americans have much lower 25(OH)D concentrations than white Americans due to dark skin pigmentation and the fact that most vitamin D comes from solar UVB exposure. In the period 2001-4, 25(OH)D concentrations for women aged 20-39 years were 14 ng/mL for blacks and 28 ng/mL for whites [3]. Vitamin D disparities has been proposed to explain black-white disparities in adverse birth outcomes [4]. Low 25(OH)D concentrations are also associated with adverse pregnancy outcomes such as preterm birth [5,6], and obesity [7]. Parathyroid hormone concentration has been found directly correlated with gestational diabetes [8], but parathyroid hormone concentrations are inversely correlated with 25(OH)D concentrations although also modified by age [9].

A vitamin D randomized controlled trial conducted with black, Hispanic, and white pregnant women in South Carolina found that it took 4000 IU/d vitamin D3 to raise 25(OH)D concentrations to above 40 ng/mL and normalize 1,25-dihydroxyvitamin D concentrations [10]. 1,25-dihydroxyvitamin D controls expression of many genes, so this function is very important during fetal development. No adverse effects were reported such as hypercalcemia.

References 1. Min CJ, Ehrenthal DB, Strobino DM. Investigating racial differences in risk factors for primary cesarean delivery. Am J Obstet Gynecol. 2015 Jan 28. pii: S0002-9378(15)00085-X. 2. Merewood A, Mehta SD, Chen TC, Bauchner H, Holick MF. Association between vitamin D deficiency and primary cesarean section. J Clin Endocrinol Metab. 2009;94(3):940-5. 3. Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med. 2009;169(6):626-32. 4. Bodnar LM. Simhan HN. Vitamin D may be a link to black-white disparities in adverse birth outcomes. Obstet Gynecol Surv. 2010; 65(4): 273–284. 5. Bodnar LM, Klebanoff MA, Gernand AD, et al. Maternal vitamin D status and spontaneous preterm birth by placental histology in the US Collaborative Perinatal Project. Am J Epidemiol. 2014;179(2):168-76. 6. Wagner CL, Baggerly C, McDonnell SL, et al. Post-hoc comparison of vitamin D status at three timepoints during pregnancy demonstrates lower risk of preterm birth with higher vitamin D closer to delivery. J Steroid Biochem Mol Biol. 2014 Nov 13. pii: S0960-0760(14)00268-4. doi: 10.1016/j.jsbmb.2014.11.013. [Epub ahead of print] 7. Drincic AT, Armas LA, Van Diest EE, Heaney RP. Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity (Silver Spring). 2012;20(7):1444-8. 8. Kramer CK, Swaminathan B, Hanley AJ, et al. Vitamin D and parathyroid hormone status in pregnancy: effect on insulin sensitivity, β-cell function, and gestational diabetes mellitus. J Clin Endocrinol Metab. 2014;99(12):4506-13. 9. Valcour A, Blocki F, Hawkins DM, Rao SD. Effects of age and serum 25-OH-vitamin D on serum parathyroid hormone levels. J Clin Endocrinol Metab. 2012;97(11):3989-95. 10. Hollis BW, Johnson D, Hulsey TC, et al. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone Miner Res. 2011;26(10):2341-57.

Disclosure I receive funding from Bio-Tech Pharmacal, Inc. (Fayetteville, AR), MediSun Technology (Highland Park, IL), and the Vitamin D Council (San Luis Obispo, CA).

On 2015 Feb 23, William Grant commented:

Vitamin D disparities may explain some of the findings regarding risk of primary cesarean delivery

The paper by Min and colleagues found many interesting results regarding correlations with primary cesarean delivery [1]. However, one additional important factor was overlooked: 25-hydroxyvitamin D [25(OH)D] concentration. This comment briefly summarizes how 25(OH)D concentrations are related to the findings of Ref. 1.

First, 25(OH)D concentrations have been found inversely correlated with primary cesarean delivery [2]. Second, black Americans have much lower 25(OH)D concentrations than white Americans due to dark skin pigmentation and the fact that most vitamin D comes from solar UVB exposure. In the period 2001-4, 25(OH)D concentrations for women aged 20-39 years were 14 ng/mL for blacks and 28 ng/mL for whites [3]. Vitamin D disparities has been proposed to explain black-white disparities in adverse birth outcomes [4]. Low 25(OH)D concentrations are also associated with adverse pregnancy outcomes such as preterm birth [5,6], and obesity [7]. Parathyroid hormone concentration has been found directly correlated with gestational diabetes [8], but parathyroid hormone concentrations are inversely correlated with 25(OH)D concentrations although also modified by age [9].

A vitamin D randomized controlled trial conducted with black, Hispanic, and white pregnant women in South Carolina found that it took 4000 IU/d vitamin D3 to raise 25(OH)D concentrations to above 40 ng/mL and normalize 1,25-dihydroxyvitamin D concentrations [10]. 1,25-dihydroxyvitamin D controls expression of many genes, so this function is very important during fetal development. No adverse effects were reported such as hypercalcemia.

References 1. Min CJ, Ehrenthal DB, Strobino DM. Investigating racial differences in risk factors for primary cesarean delivery. Am J Obstet Gynecol. 2015 Jan 28. pii: S0002-9378(15)00085-X. 2. Merewood A, Mehta SD, Chen TC, Bauchner H, Holick MF. Association between vitamin D deficiency and primary cesarean section. J Clin Endocrinol Metab. 2009;94(3):940-5. 3. Ginde AA, Liu MC, Camargo CA Jr. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med. 2009;169(6):626-32. 4. Bodnar LM. Simhan HN. Vitamin D may be a link to black-white disparities in adverse birth outcomes. Obstet Gynecol Surv. 2010; 65(4): 273–284. 5. Bodnar LM, Klebanoff MA, Gernand AD, et al. Maternal vitamin D status and spontaneous preterm birth by placental histology in the US Collaborative Perinatal Project. Am J Epidemiol. 2014;179(2):168-76. 6. Wagner CL, Baggerly C, McDonnell SL, et al. Post-hoc comparison of vitamin D status at three timepoints during pregnancy demonstrates lower risk of preterm birth with higher vitamin D closer to delivery. J Steroid Biochem Mol Biol. 2014 Nov 13. pii: S0960-0760(14)00268-4. doi: 10.1016/j.jsbmb.2014.11.013. [Epub ahead of print] 7. Drincic AT, Armas LA, Van Diest EE, Heaney RP. Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity (Silver Spring). 2012;20(7):1444-8. 8. Kramer CK, Swaminathan B, Hanley AJ, et al. Vitamin D and parathyroid hormone status in pregnancy: effect on insulin sensitivity, β-cell function, and gestational diabetes mellitus. J Clin Endocrinol Metab. 2014;99(12):4506-13. 9. Valcour A, Blocki F, Hawkins DM, Rao SD. Effects of age and serum 25-OH-vitamin D on serum parathyroid hormone levels. J Clin Endocrinol Metab. 2012;97(11):3989-95. 10. Hollis BW, Johnson D, Hulsey TC, et al. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone Miner Res. 2011;26(10):2341-57.

Disclosure I receive funding from Bio-Tech Pharmacal, Inc. (Fayetteville, AR), MediSun Technology (Highland Park, IL), and the Vitamin D Council (San Luis Obispo, CA).