Does vitamin D increase conception in couples with infertility?

This study evaluated the effects of added vitamin D to margarine on the pregnancy rates of women with infertility. This study found that women with infertility who had extra vitamin D were more likely to become pregnant compared to women who were not.

Vitamin D is needed for calcium absorption and involved in bone health. Up to half of all women of reproductive age do not have enough vitamin D. Studies indicate that higher vitamin D levels are associated with an increased likelihood of pregnancy.

Vitamin D deficiency is associated with factors related to infertility in women, such as endometriosis. Whether added vitamin D to foods such as margarine can increase chances of pregnancy for women who have infertility is unclear.

Denmark used to fortify all margarine with vitamins including vitamin D. In 1985, the program was stopped. This study compared the pregnancy rates of women treated at fertility clinics during and after margarine fortification. There were 6,313 women in the “fortification” group and 8,485 women in the “non-fortification” group. There were also 1,404 women in a “wash-out” group who were diagnosed with infertility the year fortification ended.

14.5% of women in the fortification group became pregnant within one year. 12.4% of women in the washout group became pregnant. In the non fortification group, 8.7% became pregnant.  During vitamin D fortification, the odds of getting pregnant were 87% higher.

The study authors also compared pregnancy rates by time of year. The rate of conception was consistently higher during the dark part of the year (Oct 1 – March 31).

This study concluded that pregnancy rates were higher in women who received extra vitamin D compared to women who did not.

The women in the fortification group were slightly younger than those in later groups. The fortification may also have had an effect on the male partners of women with infertility. Also, margarine fortification with vitamin E was stopped at the same time as fortification with vitamin D.

Discuss your use of supplements including vitamin D with your doctor.