Increased bioavailability of Vitamin D improved pregnancy outcomes in in vitro fertilization cycles, only in patients over 36 years: a cross-sectional study.

Objective: Vitamin D (VitD) is a secosteroid hormone showing both antiproliferative and immunomodulatory effects. Its involvement in placental steroidogenesis and endometrial decidualization even plays a role in other gynecological functions, including assisted reproductive technology (ART). However, controversial data have been reported on its implication in pregnancy outcomes during In Vitro Fertilization (IVF) programs. In order to elucidate the VitD role in ART success, we evaluated serum and follicular fluid (FF) VitD levels in infertile women concerning the pregnancy rate.

Patients And Methods: In our IVF center, 446 patients, under the age of 42 years old,  were evaluated in the period between January 2018 and December 2019. It is here important to clarify that, in order to respect the exclusion criteria, only 103 of them were enrolled for the study concerning the VitD evaluation in serum and follicular fluid at the time of the egg retrieval. This took place both in 34 pregnant patients (Group 1) and 69 non-pregnant ones (Group 2). Furthermore, the collection of these data gave us the opportunity to assess a possible correlation between the VitD levels and the achievement of pregnancy in the performed IVF cycles.

Results: The studied group included 103 eligible women. The average age for Group 1 was 33.12 ± 3.72 yrs whereas 33.72+3.99 yrs (p=0.467) for Group 2. The main differences were observed concerning follicle numbers of 17-21 mm (p=0.0043), the number of retrieved oocytes (p=0.0207), as well as the number of mature oocytes (p=0.0233) among the different groups. Different reference ranges, established according to the pregnancy outcomes, revealed that pregnant women with >36 yrs showed significantly higher levels of VitD.

Conclusions: Increased serum and FF-VitD levels in women undergoing IVF with age ≥36 yrs, were significantly associated with a favorable outcome to achieve and carry on with the pregnancy.