Effect of vitamin D status on clinical pregnancy rates following in vitro fertilization

Abstract

CMAJ OPEN, 1(2) E77Research CMAJ OPEN I nfertility affects 15% of couples in North America. 1 Recent studies support the role of vitamin D in human reproduction and suggest that vitamin D levels predict reproductive success following in vitro fertilization (IVF). 2,3Vitamin D is a prohormone that is acquired exogenously from the diet or produced endogenously in the skin. Vitamin D is metabolized primarily in the liver to 25-hydroxy-vitamin D (25[OH]D), the serum concentration of which can be used as an indicator of vitamin D status. The classification of vitamin D status varies in the literature, 2,4,5 and because the relation between vitamin D and fertility has only recently been investigated, no specific cut-off values have been referenced in the literature. However, a Canadian guideline defined vitamin D deficiency as levels below 25 nmol/L, insufficiency as levels between 25 and 74 nmol/L, and sufficiency as levels of 75 nmol/L and greater. 6 Lower levels of vitamin D (< 75 nmol/L) have also been associated with a higher incidence of certain types of cancer and impaired immune response. 4,5 People living in countries at higher latitudes, such as the United States and Canada, are more prone to vitamin D insufficiency, especially during the winter months.7 Vitamin D insufficiency is highly prevalent in women of reproductive age.2,7 A Canadian study by Veith and colleagues 7 reported that 25.6% of nonwhite and 14.8% of white women of reproductive age (18-35 yr) had insufficient vitamin D levels (defined as < 40 nmol/L). Ozkan and colleagues 2 reported a 36% prevalence of vitamin D insufficiency (50-74 nmol/L) and a 27% prevalence of deficiency (< 50 nmol/L) among women of reproductive age with infertility. 2 Anifandis and colleagues 8 reported that the prevalence of vitamin D insufficiency (20.1-30 ng/mL) or deficiency (< 20 ng/mL) was 79% in a population of women undergoing IVF. The link between vitamin D status and reproduction has been largely shown in murine models. [9][10][11][12] In an early study by Halloran and Deluca, 9 female rats were fed diets that were sufficient or deficient in vitamin D. The rats were then mated

Vitamin D and assisted reproduction: should vitamin D be routinely screened and repleted prior to ART? A systematic review

“…Garbedian et al [72] confirmed these findings in their study of a group of infertile Canadian women who subsequently underwent oocyte retrieval. Women who were vitamin D deficient were grouped together with those who were vitamin D insufficient, due to an inadequate sample size in the deficient group (1.2 and 53.8 %, respectively).…”

“…As Vanni et al [80] reported, a lower prevalence of vitamin D deficiency is to be expected in a population of women seeking IVF, as these women tend to have higher socioeconomic status as well as education level, both of which are factors associated with higher vitamin D levels. Garbedian et al [72] suggested that the low number of vitamin D deficient women reported in their study (1.2 %) was due to increased usage of daily prenatal vitamins. However, a majority of their participants (55 %) did not meet criteria for vitamin D repletion despite supplementation.…”

“…Only eight of the 34 articles retrieved from PubMed met criteria (Fig. 2) [66][67][68][69][70][71][72][73]. Reference lists of chosen studies and narrative reviews were cross-referenced to find additional studies.…”

“…A societal perspective was employed and only estimated direct costs were considered. Vitamin D deficiency was defined as <20 ng/mL in accordance with the Endocrine Society guidelines [7], and also consistent with the definition utilized by the majority the trials included in this review [67][68][69][70][71][72]. The study by Polyzos et al [73] was selected for utilization of clinical pregnancy and ongoing pregnancy rates for mathematical modeling secondary to reporting the largest cohort, recency of publication and attempting to control for embryo quality and quantity by including single blastocyst ART cycles only.…”

“…However, only six of these categorized serum vitamin D levels according to the ranges set forth by the Endocrine Society [67][68][69][70][71][72] (vitamin D deficiency <20 ng/ml, insufficiency 20-30 ng/ml, and replete >30 ng/ml). When the prevalence of each category reported by each of these six studies were weighted for sample size and subsequently averaged, 27.7 % were vitamin D deficient, 38.4 % were insufficient, and 33.8 % were replete.…”