Around 35 percent of expectant mothers may be at risk of pregnancy complications - such as miscarriage or preterm birth - as a result of iron deficiency. This is the conclusion of a new study published in the European Journal of Endocrinology.

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Researchers found around 10 percent of pregnant women with iron deficiency have thyroid problems.

Iron deficiency is a common form of anemia, arising when the body does not have enough iron - a mineral present in a number of foods, including beef, beans, nuts, whole grains, and dried fruits.

According to the World Health Organization (WHO), more than 30 percent of the global population are anemic, with most cases attributable to iron deficiency.

For adults aged 19-50 years, the National Institutes of Health (NIH) recommend a daily iron intake of 8 milligrams for men and 18 milligrams for women, rising to 27 milligrams during pregnancy.

As a result of iron deficiency, the body produces insufficient levels of hemoglobin - a protein in red blood cells that carries oxygen from the lungs to the body's tissues. This can lead to tiredness and lack of energy, shortness of breath, chest pain, heart palpitations, and a pale complexion.

According to lead author Dr. Kris Poppe - head of the Endocrine Clinic at Saint-Pierre University Hospital (ULB) in Brussels, Belgium - iron deficiency can be especially harmful for expectant mothers and their offspring; women need more iron during pregnancy in order to make the additional blood cells needed for fetal and placental growth.

Iron also aids the functioning of a protein called thyroid peroxidase (TPO), which is crucial for the production of thyroid hormone. Pregnant women need to produce enough thyroid hormone in order for their babies' brains to fully develop. This is particularly important in the first trimester of pregnancy, when the fetus has yet to develop its own thyroid gland.

10 percent of iron-deficient pregnant women had thyroid autoimmunity

For their study, Dr. Poppe and colleagues set out to investigate the scale of iron deficiency during pregnancy, and how this might be linked to the development of thyroid problems.

To reach their findings, the researchers monitored 1,900 women during their first trimester of pregnancy.

The team measured the women's blood levels of the protein ferritin (an indicator of iron levels), levels of antibodies against TPO (an indicator of thyroid autoimmunity, where the immune system mistakingly attacks healthy thyroid cells), levels of the thyroid hormone free thyroxine (FT4), and levels of thyroid stimulating hormone (TSH).

The researchers found that 35 percent of the expectant mothers had iron deficiency, of whom 10 percent had thyroid autoimmunity. Among pregnant women without iron deficiency, 6 percent had thyroid autoimmunity.

What is more, measurements of TSH levels showed that 20 percent of the pregnant women with iron deficiency had subclinical hypothyroidism, where TSH levels are mildly elevated, compared with 16 percent of those without iron deficiency.

The results remained after accounting for the women's age and body mass index (BMI), the team reports.

The researchers say their findings show that iron deficiency remains a major issue, and they suggest increased focus on identifying and addressing iron deficiency during pregnancy.

Medical News Today asked Dr. Poppe what his advice would be for expectant mothers who are concerned about the risks associated with iron deficiency:

"To check their levels before pregnancy and [make it] a priority to increase their intake of food rich in iron. Depending on the area, city, or country where the women live, it can be advised to start multivitamin products (containing iron) before pregnancy."

Dr. Kris Poppe

The researchers now plan to investigate whether iron deficiency and/or thyroid autoimmunity among the women influenced pregnancy outcomes.

They also want to establish cause and effect; does iron deficiency trigger thyroid autoimmunity, or does thyroid autoimmunity cause iron deficiency? They note that previous studies indicate the first proposition is most likely.

Learn about the health benefits of iron.