The link between selenium intake during pregnancy, fetal development, and birth weight

The link between selenium intake during pregnancy, fetal development, and birth weightSelenium is an essential trace element that supports a host of different proteins and antioxidants that are important for pregnancy. According to a new Norwegian population study that is published in the science journal Nutrients, lack of selenium during pregnancy may stunt the growth of the fetus and result in low birth weight. This may have consequences for the child’s growth, cognitive skills, and health. Selenium deficiencies are rather common in Norway and the rest of Europe and that is a problem.

If a fetus grows at a slower rate than normally, there is an increased risk of serious complications. If the stunted growth occurs during the early part of pregnancy, the risk is greater. Stunted growth raises the risk of the fetus dying in the womb, and there is also an increased risk that the newborn baby has an oxygen shortage (perinatal asphyxia) with subsequent complications. Later in life, this may lead to short stature, delayed cognitive development, diabetes, and cardiovascular disease.
It is known that smoking, substance abuse, hypertension, preeclampsia, and thyroid disorders increase the risk of stunted growth. However, the diet also plays a role because the fetus needs a number of different nutrients during the period of development and growth. For instance, the trace element selenium supports around 25-30 selenium-dependent proteins that control functions like energy turnover, DNA synthesis, and metabolism. Studies even suggest that these selenium-containing proteins have a specific role in tissue development during pregnancy, including the development of the brain. Moreover, the selenium-containing GPX antioxidants (glutathione peroxidases) help protect the placenta and the fetus against oxidative stress caused by free radicals.
Earlier studies show that lack of selenium increases the risk of premature delivery, which in itself is associated with low birth weight. The whole purpose with the large Norwegian population study was to look closer at whether selenium intake during pregnancy and levels of selenium in the blood were related to fetal development and birth weight.

Selenium deficiency is common among pregnant women

The Norwegian cohort study (Mor, Far og Barn) studied pregnant women from all over Norway during the period from 1999 to 2008. They were invited to join the study in connection with an ultrasound scanning in their 18th week of pregnancy. Those who consented were asked to answer questionnaires several times in the course of their pregnancy and the period where their babies grew up.
Using data from this study (MoBa) and data from the Medical Birth Registry of Norway (MBRN), the researchers looked at the relation between 71,728 pregnant women’s selenium intake from the diet and from supplements during the first half of their pregnancy, their blood selenium status halfway through their pregnancy, the size of the fetus, and the babies’ birth weight.
It turned out that around half the pregnant women had a daily selenium intake that was below the official Norwegian recommendation of 60 micrograms per day. And around half the woman had blood levels that were below the threshold level of 100 micrograms per liter of blood.

Selenium’s role in fetal development

According to the study, eating a selenium-rich diet during pregnancy had a greater positive effect on fetal growth and birth weight than any other single factor. However, selenium supplementation and blood levels of the nutrient did not have any impact. It is worth mentioning that most of the pregnant women supplemented with inorganic selenium, which it is difficult for the body to utilize.
The researchers point to several flaws and limitations in the study and state that more studies are needed to show how low maternal selenium status can affect fetal growth. Nonetheless, previous research shows that supplementation with selenium yeast that contains a variety of organic and highly bioavailable selenium species has other positive effects during pregnancy.

Supplements with selenium yeast contribute to a healthy pregnancy in several ways

Pregnant women who take 100 micrograms of selenium yeast daily from their first trimester until delivery are able to lower the risk of a ruptured fetal membrane by around 30 percent, according to a placebo-controlled study that is published in Journal of Obstetrics and Gynaecology.
In addition, it appears that pregnant women who got selenium yeast had a lower rate of preeclampsia, which is normally the leading cause of premature delivery. Preeclampsia can also lead to life-threatening conditions like eclampsia.
A team of international scientists with the participance of Denmark has conducted a large study that shows a possible link between selenium deficiency and premature delivery.

It is quite interesting that Danish pig and livestock farmers since the 1970s have been supplementing the animals with selenium as a way of preventing different deficiency symptoms – including impaired fertility.

Selenium sources, widespread deficiencies, and bioavailable supplements

Selenium is primarily found in fish, shellfish, offal, eggs, dairy products, Brazil nuts, and green vegetables. The agricultural soil in most of Europe, Denmark included, is generally very low in selenium, which is clearly reflected in the crops and the entire food chain. This is why farmers have been giving extra selenium to their livestock for decades. Although fish and shellfish are generally regarded as good selenium sources, even a diet with plenty of these foods is unable to provide enough selenium to cover our actual needs. Also, women who are trying to conceive, who are already pregnant, or who are breastfeeding should be careful with their intake of predatory fish such as tuna or salmon from the Baltic Sea because they often have a relatively high content of mercury and other environmental toxins.
An estimated 20 percent or so of the Danes get less selenium that the daily reference intake (RI) level, which is currently 55 micrograms.
Many experts say that we need as much as 100 micrograms per day. This amount is what is required for proper saturation of selenoprotein P, a selenoprotein that is used as a marker of the body’s selenium status.
It is generally advisable to supplement with selenium yeast that contains a variety of organic selenium species because it is the closest you can get to eating a balanced diet with many different selenium sources. You can find combined supplements with selenium yeast that are made especially for pregnant women.

Fetal growth and various types of stunting

  • AGA (Appropriate for Gestational Age): Fetus has normal weight in relation to gestational age (the actual age of the fetus)
  • SGA (Small for Gestational Age): The fetus is small, and it is often due to genetic factors
  • IUGR (Intrauterine Growth Retardation): The fetus has not reached its genetically determined growth potential
  • If stunting is suspected, the expecting mother should consult the hospital or clinic where she is expected to give birth

Referencer:

Pol Solé-Navais et al. Maternal Dietary Selenium Intake during Pregnancy Is Associated with Higher Birth Weight and Lower Risk of Small for Gestational Age Births in the Norwegian Mother, Father and Child Cohort study. Nutrients. December 2020

Aparna Shreenath. Selenium Deficiency. StatPearls. May 6, 2019

Hilten T Mistry et al. Selenium in reproductive health. Journal of Obstetrics and Gynaecology. 2011

Fatemeh Tara et al. Selenium supplementation and premature (pre-labor) rupture of membranes: a randomized double-blind placebo-controlled trial. Journal of Obstetrics and Gynaecology. 2010

Jones GD et al. Selenium deficiency risk predicted to increase under future climate change. Proceedings of the National Academy of Sciences 2017
Editorial team. Selenium deficiency promoted by climate change. ETHzüric 2017

Danmarks Jordbrugsforskning. Selen anvendelse i dansk landbrug. 2006

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