Vitamin B7 (Biotin)
Although some reports indicate up to half of pregnant women may be slightly biotin deficient in comparison to what may be needed during pregnancy, all biotin required for pregnancy can be obtained through a varied diet. This is important, as not all prenatal vitamin formulations include biotin.
Initial concern regarding biotin deficiency and pregnancy originated from findings of animal studies that deficiency was harmful to embryos, and could therefore potentially cause birth defects in humans.
However, it has not been found that human development is affected, and biotin deficiency in humans eating a mixed diet has never been reported. (Animal studies are not always applicable to humans.)
Women should also note that while supplementation of biotin in the non-pregnant population for hair and nail growth is common, this is not recommended during pregnancy due to a lack of research that supplementation would have any benefit during pregnancy.
Further, high biotin levels in the blood – such as through supplementation – can interfere with certain lab tests, causing falsely high or low results depending on the test.
Women need to tell their health care provider (HCP) if they are taking biotin supplementation, and they should never start any kind of supplementation without talking to their HCP first.
Background
Biotin is a water-soluble essential vitamin that plays a key role in protein modifications, gene regulation, and cell signaling. It is also required for cell growth and replication, which is necessary for fetal growth and development.
Pregnancy
While cell growth and replication is a requirement of human development, researchers are attempting to identify biotin's specific role during pregnancy, which could help determine biotin requirements. However, as of September 2020, biotin's role remains unclear.
In one animal study assessing the effects of biotin deficiency during pregnancy, 100% of rat offspring developed cleft palate or limb shortening. Further, in studies assessing the effectiveness of folic acid in the reduction of neural tube defects, biotin was given in addition to folic acid.
Despite the above findings, which technically could indicate a role of biotin in neural tube, limb, and facial development, actual requirements are very difficult to determine, as research is inconsistent, animal studies are not always applicable to humans, and methods of measuring biotin status in pregnant women conflict.
Urine and blood tests for biotin status during pregnancy contradict each other (one indicates a deficiency while another indicates adequate supply); it is theorized a woman's body may adjust and recalculate its needs and reabsorption of biotin during pregnancy, but the exact reasons for this are also unclear.
Although no reliable measurement methods have been established, there is some research that indicates borderline biotin deficiency may occur in 30% to 50% of pregnant women, especially in the first trimester, and some researchers have indicated it is possible that a biotin intake at least two to three times the average intake may be needed to meet the requirement of pregnancy.
However, due to a lack of consistent evidence and intense debate surrounding biotin and pregnancy, biotin daily recommendations remain the same for pregnant and non-pregnant women at 30 micrograms (mcg)/day (not all prenatal vitamins contain biotin).
Deficiency
Biotin deficiency has never been reported in human pregnancies, and therefore the risk of damage to the fetus is estimated to be low or nonexistent. However, researchers cannot rule out that slight deficiency could cause birth defects, but significantly more research is necessary, to include what type of birth defects supplementation could prevent.
When deficiency does occurs (usually through starvation), signs and symptoms may include thinning hair (hair loss), a scaly red rash around the eyes, nose, mouth and perineum, eye infections, seizures, depression, and brittle nails.
Supplementation
Supplementation of biotin during pregnancy is not recommended due to its wide abundance in foods and the rarity of its deficiency. Although supplementation is not expected to be harmful to a developing fetus, supplementation has not been studied during human pregnancy.
Additionally, many dietary supplements promoted for hair, skin, and nails contain biotin levels up to 650 times the recommended daily intake of biotin. Although this daily amount has not been shown to be harmful in non-pregnant individuals, supplementation, again, has not been studied in pregnancy, and no potential benefit of supplementation during pregnancy has been identified.
Note: High levels of biotin in dietary supplements can cause clinically significant incorrect lab test results, such as falsely high or falsely low results, due to laboratories using biotin technology to bind to specific proteins.
Women need to tell their HCP if they are taking biotin supplements during pregnancy. Women should also never start taking biotin supplements without speaking to their HCP first.
Food Sources
A typical balanced diet provides approximately 35 to 70 mcg of biotin/day, but biotin content of most foods has not been determined so this is only an estimate.
Many foods contain at least some biotin to include pork chops, egg yolks, fish (salmon), beef, turkey, seeds, nuts, and sweet potatoes.
Note: A high consumption of egg whites (not yolks) can block biotin absorption.
Action
Women need to tell their HCP if they are taking biotin supplements; they also need to talk to their HCP prior to taking any biotin supplementation during pregnancy.
Women also need to speak with their HCP if they are concerned about the growth of their hair or nails during pregnancy, or if they have any questions regarding their overall diet and nutrition.
HCPs can help assess a woman's overall diet to recommend possible changes that may improve her nutrition during pregnancy.
Resources
Biotin Fact Sheet (Oregon State University)