Vitamin D in pregnancy

During pregnancy and lactation, the eating habits and lifestyle of the future mother are very important, not only for the maintenance of the woman’s health, but also to prevent disorders and diseases to the fetus first and then to the newborn.

In this phase, in particular, the need for energy, macronutrients and micronutrients increases; It is therefore important, for example, to ensure the right intake of vitamins (such as folate) and mineral salts (for example calcium, phosphorus, iron).

Among the micronutrients that in recent years have become the subject of greater attention during gestation, there is undoubtedly vitamin D. The role of vitamin D in the field of human reproduction has been recognized for over twenty years, although it has not yet been fully explored. But some studies have highlighted the possible consequences of a deficiency of this nutrient.

A fat-soluble vitamin

Vitamin D, also called calciferol, belongs to the group of fat-soluble vitamins, that is, those that are absorbed together with dietary fats and accumulated in the liver. It is produced by the body from cholesterol derivatives present in the skin thanks to the action of the sun’s rays (but it is also found in some foods of animal origin).

This vitamin regulates in particular the metabolism of calcium (it promotes its absorption in the intestine and reabsorption in the kidney), promotes intestinal absorption of phosphorus and stimulates the processes of correct mineralization of the skeleton.

A vitamin D deficiency can cause rickets in children (skeletal disease that involves bone fragility and can lead to fractures and deformations), resulting in stunting, and osteomalacia (a strong form of bone decalcification) in adults.

Normal sun exposure is generally sufficient to cover the need for this vitamin in adults: generally it is enough to expose at least the arms for 10-40 minutes a day, also in relation to the season and the color of the skin, avoiding, in summer, the central hours in which the peak of ultraviolet rays increases the risk of skin cancer.

With food, on the other hand, low levels of vitamin D are generally introduced, also because food sources are relatively few such as cod liver oil (which is the richest food), fatty fish (such as salmon or mackerel), egg yolk, some cheeses (which, however, contain not high levels).

The following table lists some of the foods with the highest vitamin D content:

Stay away from infections

Vitamin D deficiencies expose you to the risk of bacterial vaginosis which, if contracted during pregnancy, can increase the possibility of complications and premature births. This is supported by a study by the University of Pittsburgh published in the Journal of Nutrition, which showed that 41% of the participants had bacterial vaginosis and, of these, 93% had insufficient levels of vitamin D.

The protective action of vitamin D against vaginal infection, the researchers explain, could refer to the immune system support activity carried out by this substance.

This is a preliminary study, so it is not justifiable to recommend pregnant women to take high doses of vitamin D, but it is right to advise them to talk to their doctor to check plasma levels of this vitamin.

In defense of the placenta

But infections in pregnancy can also involve the placenta. For this reason, supplementing the diet during pregnancy with vitamin D supplements can protect the placenta, strengthening its natural immune defenses.This is confirmed in Biology of Reproduction by a study by the University of California at Los Angeles (UCLA) which highlighted how the presence of vitamin D stimulates the production of cathelicidin at the level of cells destined to give rise to the placenta. Cathelicidin, a protein with antimicrobial properties, is able to counteract the development of a wide range of pathogens, such as staphylococci, streptococci, Escherichia coli.

Vitamin D deficiencies: risk of caesarean section…

On the other hand, according to researchers at Boston University School of Medicine and Boston Medical Center, vitamin D deficiency would not only increase the risk of infections, but also that of having to resort to a caesarean section.

Risk that, according to the study, published in the Journal of Clinical Endocrinology & Metabolism, is quadrupled in pregnant women who have vitamin D deficiency. According to experts, it could be involved the increase in blood pressure, or the general reduction in muscle strength that accompany vitamin D deficiency.

… and problems with unborn children

The discovery is made by a Japanese team: low intake of vitamin D during pregnancy can cause cranial laxity in newborns. It is a softening of the bones of the skull that is usually considered a physiological condition that does not require treatment.

But, if vitamin D deficiency persists even during breastfeeding, this condition is destined to continue and cause complications in childhood, such as reduction of bone mass, type 1 diabetes and weakening of the immune system.

And, finally, avoiding vitamin D deficiency during pregnancy is also good for the dental health of children. To demonstrate for the first time at a scientific level a link between the intake of vitamin D in pregnancy and the health of the teeth of the unborn child were some Canadian researchers from the University of Manitoba.

It is good to keep in mind that during pregnancy and lactation the body requires a greater supply of calcium, whose absorption is favored by vitamin D.

Compensating for any deficiencies with appropriate supplements, not only allows the bones of the child – and as we have seen also the teeth – to develop at their best, but allows to provide for the increased maternal needs in this delicate phase, safeguarding the state of health.

Further studies will be needed

The need for further studies investigating the need for vitamin D supplementation in all pregnant women has also been reiterated by a recent systematic review conducted by the Cochrane Collaboration, the international non-profit and independent body, an important reference point for the scientific world, whose purpose is to collect, critically evaluate and disseminate information relating to the effectiveness and safety of health interventions.

This review confirms that studies provide evidence of benefits from vitamin supplementation, especially in reducing the risk of low birth weight, preterm birth and preeclampsia (also called gestosis), a pregnancy disorder characterized by increased blood pressure and diffuse swelling, which can compromise the natural continuation of gestation.

On the other hand, however, the review also highlights how the possible supplementation of vitamin D combined with calcium increases the risk of preterm birth. In addition, data on adverse effects of supplementation would be lacking in all studies, so further rigorous evidence is required.

Also for this reason, at the moment there are no official recommendations indicating the need to routinely resort to vitamin D supplementation during gestation. The only vitamin for which this happens is folic acid (or vitamin B9), which has long been recommended in medicine starting one month before conception and during pregnancy by virtue of the documented benefits it entails. Folic acid has in fact been recognized as essential in the prevention of some congenital malformations, particularly those affecting the neural tube, such as spina bifida.

Vitamin D in pregnancy: how much you need

The recommended dose of vitamin D during pregnancy and lactation is 600 IU per day (equivalent to 15 μg per day).

The Italian Medicines Agency makes it known that in a healthy woman with a correct and varied diet it is not indicated to carry out a specific vitamin D supplementation during the nine months.

The use of supplements is recommended only in women who belong to categories at risk of deficiency, ie women from Southeast Asia, Africa, the Caribbean and Middle Eastern origins, women who rarely expose themselves to the sun or women who follow a diet low in vitamin D.

However, vitamin D deficiency must first be documented through a blood test (the amount of 25 hydroxyvitamin D, also referred to as 25(OH)D, is sought). If the dosage of the nutrient confirms the deficiency, it is up to the doctor to prescribe the most suitable products for the treatment of the deficiency.