P-594 A prevalence study of vitamin D insufficiency among infertile women in Sweden, its determinants and IVF outcome.
Authors: Tsiartas P , Maaherra Armstrong P , Thurin-Kjellberg A , Augustin H , Bärebring L , Osmancevic A , Bullarbo M 
Published: June 2023

Abstract

Study question
What is the prevalence and the determinants of vitamin D insufficiency and do women with insufficiency have worse IVF outcome compared with them with sufficiency?

Summary answer
Women from Non-Nordic countries, with avoiding sun behavior and low intake of vitamin supplementation have higher prevalence of vitamin D insufficiency but comparable IVF outcome.

What is known already
Vitamin D seems to have an important role in human reproduction and infertility. Vitamin D insufficiency is highly prevalent around Europe, yet studies from north latitude countries, where sunlight exposure is undetectable during the winter, describing the prevalence and determinants of this condition in women with infertility lacking.
Moreover, there is still discrepancy in the existing evidence whether insufficient vitamin D status is associated with poor IVF/ICSI outcome and no published studies in this field exist from Nordic countries.

Study design, size, duration
Prospective cohort study that was conducted between September 2020 and August 2021 at Reproductive Medicine, Sahlgrenska University Hospital, Gothenburg in Sweden. Gothenburg is a city located in southwestern Sweden (latitude 57.7o N) with highly variating duration of daylight between seasons.

Participants/materials, setting, methods
Women with infertility who were scheduled for IVF/ICSI treatment were included. Venous blood samples for measurement of serum 25(OH) vitamin D concentration and questionnaires assessing vitamin D intake and sun exposure habits were collected from 265 women.

Main results and the role of chance
The overall prevalence of vitamin D insufficiency was 27%, ranging from 7% in summer to 33% in winter.
The odds for vitamin D insufficiency were higher for women originating from non-Nordic Europe (OR 3.33, 95% CI 1.26-8.80, adjusted p=0.015), Middle East (OR 14.46, 95% CI 5.20-40.20, adjusted p&lt;0.001) and Asia (OR 6.46, 95% CI 1.79-23.27, adjusted p=0.004) compared with women originating from Nordic countries. It was more likely for women who did not use vitamin D supplements to have insufficiency compared with them using supplements (OR 3.48, 95% CI 1.69-7.20, adjusted p&lt;0.001). The odds for vitamin D insufficiency were also higher for women staying “in the shade all the time” compared with women who were exposing themselves “in the sun all the time” (OR 3.65, 95% CI 1.43-9.27, adjusted p=0.007) and with them staying “both in the sun and shade” (OR 3.57, 95% CI 0.88-14.43, adjusted p=0.074).
The reproductive outcome of IVF/ICSI treatment between women with serum 25(OH) vitamin D insufficiency and sufficiency was comparable.

Limitations, reasons for caution
The use of a questionnaire has intrinsic limitations (recall bias, low accuracy of the provided information). Moreover, the questionnaire did not include questions about sun protection factor usage during sun exposure. Blood sampling was underrepresented during summer due to limited resources during the summer months with closed IVF clinics.

Wider implications of the findings
Pre-IVF/ICSI treatment vitamin D serum concentration do not seem to influence IVF success. However, information about vitamin D should target women from non-Nordic countries and to advise them for supplementation and sun exposure. The aim is to avoid vitamin D insufficiency and the associated adverse long-term health consequences.

Trial registration number
not applicable