Iodine deficiency linked to delayed conception

Women who have moderate to severe iodine deficiency have a 46% less chance of getting pregnant as compared to women who have normal iodine levels says the results of the Longitudinal Investigation of Fertility and the Environment (LIFE) study, a population-based prospective cohort study published in recent issue of Human Reproduction.

This is the first study to investigate a link between iodine levels and chances of conception in women desiring to start a family.

The researchers interviewed and enrolled 501 women over a period of 5 years.  Urine samples of all the participants were collected at the start of the study for measuring iodine levels and these women reported on risk factors for infertility during the interview. The women were advised timed intercourse according to ovulation monitoring by various fertility trackers for a period of 1 year.

Pregnancy was detected with digital home pregnancy test around menstruation.

At 1 year, 72% women (332) conceived while 42 women could not, and the rest decided to leave the study.

It was seen that nearly 56% of women had sufficient iodine levels, while 44% of women had iodine deficiency, of whom nearly 25% samples were in range of moderate to severe iodine deficiency.

The researchers used fecundability odds ratio (FOR) to measure a couple’s chance of getting pregnant in a menstrual cycle. A FOR of less than 1 suggests that the couple will take longer time to achieve pregnancy, while FOR ratio more than 1 indicate a shorter time to pregnancy.

In this study, women with moderate to severe iodine deficiency had a 46% reduction in odds of conception as compared to women with adequate levels. (Adjusted FOR = 0.54)

According to National Institute of Health (NIH), RDA of iodine for pregnant and lactating women are 220 mcg and 290 mcg respectively, but no specific recommendation is made for women trying to get pregnant.  

According to WHO, a urinary iodine levels less than 150 mcg/L are considered insufficient while levels between 150–249 mcg/L indicates adequate iodine nutrition during pregnancy. About 30% of US women of childbearing age have iodine deficiency.

In pregnant women, iodine is necessary for brain development and is the most common cause of preventable mental retardation worldwide. It also causes miscarriage and stillbirths. Chronic, severe iodine deficiency in utero causes cretinism, a condition characterized by mental retardation, deaf mutism, motor spasticity, stunted growth, delayed sexual maturation, and other physical and neurological abnormalities.

This study does not prove causality, future studies are needed to replicate the findings.

It is also difficult to test women for iodine levels and give advice on iodine levels. The issue of iodine deficiency has not yet been addressed in women who are trying to conceive. 

The authors conclude that choosing a diet adequate in iodine is the key to avoid deficiency and some experts believe that consuming prenatal vitamins with iodine can address the problem of iodine deficiency in pregnancy.

Abstract 

Media courtesy: Mercola.com