Tech UPTechnologyHow can allergies affect a pregnancy?

How can allergies affect a pregnancy?


What happens during pregnancy?

During pregnancy, the mother undergoes changes in her immune system to prevent her own defenses from identifying the fetus as something foreign and eliminating it. These necessary mechanisms are specific for each stage of pregnancy , according to the needs at each moment.

Some processes of the first trimester , such as the development of the placenta and the growth of the embryo, require an immune microenvironment (environment, cells and molecules that are in contact with the fetus) of a proinflammatory type. It is also known that there is a close communication for the creation of the vascular system that feeds the embryo.

However, the proinflammatory response must be stopped during the second trimester of pregnancy, where cells called regulatory T lymphocytes have precisely this function: to create a tolerant environment against elements inherited from the father . T lymphocytes are white blood cells that coordinate the activity of other cells of the immune system.

The cells of the fetus are not 100% identical to the cells of the mother, since half of the genetic information is inherited from the sperm . In this second trimester, the embryo needs to grow and mature without being attacked by the cells of the mother’s immune system.

Finally, during the third trimester , the immune environment transforms toward a type 1 response . This is a controlled inflammatory response where maternal immune cells are recruited to contribute to uterine contractions, labor and placental abruption.

All these processes and changes require perfectly regulated transitions during which there is a very intricate communication between the two parts: the maternal immune system and the embryonic cells of the fetus .

Although it has not been detected that these exchanges involve IgE antibodies, which are responsible for causing allergies, effects on the fetus have been found when the mother suffers from some type of allergy .

How do allergies affect the fetus?

Allergies affect between 18 and 30% of the adult population , and among them, women of childbearing age. The risk of developing allergies during childhood is higher in men, but during adolescence it changes towards a higher risk in women .

Allergies during pregnancy have been associated with perinatal problems such as preterm birth, low birth weight, and preeclampsia . Many studies have attempted to detect IgE in the placenta, umbilical cord, and newborn blood, without success.

Therefore, although the clinical effects and risks to the fetus are evident, the mechanism by which it occurs remains a mystery. It is possible that the mother’s immune system is “hyper-activated” due to the allergy and this affects the necessary balance of the uterus.

Therefore, it is vitally important that allergy symptoms are controlled during pregnancy, both for the good of the mother and the future newborn. Here we bring a review of what is recommended if you suffer:

  • Asthma
  • atopic dermatitis
  • allergic rhinitis
  • anaphylaxis

What to do if you have asthma and are pregnant?

Asthma is one of the most common allergies that are poorly controlled in pregnancy. If the mother has asthma, there is an increased risk of preeclampsia (high blood pressure that prevents the fetus from getting enough blood) , caesarean section, premature birth, and the newborn developing asthma as well.

It is quite common that even if the mother has her asthma under control, it gets worse during pregnancy. In these cases, asthma attacks should be treated in the same way as they would be done outside of pregnancy: minimize the risk and reduce symptoms with the usual medications.

What happens with atopic dermatitis in pregnancy?

The European Task Force on Atopic Dermatitis (ETFAD) recommends the following steps: moisturizing creams followed by topical corticosteroids type II or III for two weeks or up to a maximum of 200 grams.

If this is not enough, ultraviolet B (UVB) phototherapy or calcineurin inhibitors (such as cyclosporin A) may be additional treatments. Ultimately, a systemic approach such as oral drugs may be considered.

allergic rhinitis during pregnancy

The best way to treat the symptoms of allergic rhinitis during pregnancy should be the same as for the general population. Avoid the allergen as much as possible and use nasal corticosteroids and antihistamines .

Rhinitis may worsen during pregnancy due to an inflammation of nasal polyps known as sinusitis . In these cases, the additional use of oral drugs , such as omalizumab, used for severe allergies is advisable.

Anaphylaxis during pregnancy

The use of an epinephrine autoinjector is the only current treatment for anaphylactic shock, also for pregnant women. However, there are some special considerations that need to be taken into account.

In the event of anaphylaxis, (1) the pregnant woman should be placed on her left side to ensure blood flow to the uterus is maintained, (2) maintain blood pressure above 90 mHg, and (3) monitor heartbeat. fetus while treating the mother.

A good diagnosis to choose the treatment

Allergies are among the most frequent chronic diseases during pregnancy . The decision about treatment should be similar to that made in non-pregnant patients with a similar age range and clinical characteristics.

In addition, it is vitally important that women receive information about the potential risks or lack of evidence for some drugs, so that they can make an informed decision. To achieve this, it is also necessary that health professionals receive the required training and updates on advances in allergy research during pregnancy.


Pfaller et al. 2021. Management of allergic diseases in pregnancy. Allergy. doi: 10.1111/all.15063

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