Psoriasis is a chronic autoimmune skin condition characterized by the rapid turnover of skin cells, leading to the formation of thick, red, and scaly patches known as plaques. The development of these plaques is driven by inflammation. The relationship between psoriasis and pregnancy is highly variable, with some women experiencing relief and others seeing their condition worsen. Understanding the body’s internal changes during gestation helps explain the complex effect pregnancy has on psoriasis.
New Onset Versus Exacerbation
Pregnancy can potentially trigger psoriasis, but the development of new onset psoriasis during this time is uncommon. Psoriasis is primarily genetic, meaning a person must already have a predisposition for the disease to manifest. In rare instances, the hormonal and immunological shifts that occur during pregnancy may serve as the environmental spark that ignites the condition.
The more typical scenario involves a change in the severity of pre-existing psoriasis. Studies indicate that 40% to 60% of women report an improvement in symptoms during pregnancy, often starting in the second and third trimesters. This improvement is thought to be a direct result of the physiological changes occurring to maintain the pregnancy.
Conversely, 10% to 20% of women experience a worsening of their psoriasis during gestation, while the remaining women observe no change. This variability emphasizes that each individual’s response to pregnancy is unique. The most common period for a flare-up is not during pregnancy itself, but rather in the postpartum period, with over 50% of women experiencing a worsening of their psoriasis within six weeks after delivery.
The Role of Immune System Shifts
Changes in psoriasis severity are primarily linked to the body’s necessary immune system adjustments during pregnancy. Psoriasis is driven by an immune response heavily influenced by T-helper 1 (Th1) cells. These Th1 cells produce pro-inflammatory signaling molecules that perpetuate the skin inflammation characteristic of psoriasis.
Successful pregnancy requires the mother’s immune system to shift away from pro-inflammatory Th1 dominance to T-helper 2 (Th2) dominance. This switch is a protective mechanism that prevents the mother’s body from rejecting the developing fetus. Pregnancy hormones, particularly high levels of estrogen, are believed to drive this Th1-to-Th2 shift.
As the immune system shifts to this Th2-dominant state, the underlying inflammatory drive of psoriasis is often suppressed, leading to symptom improvement. This improvement is typically seen in the later trimesters when hormonal changes are more pronounced. Once the baby is delivered, the immune system quickly reverts to its pre-pregnancy state, causing a rapid rebound of Th1-mediated inflammation. This rebound explains why psoriasis flares are common in the weeks immediately following childbirth.
Treatment Safety During Gestation
Managing psoriasis during pregnancy requires careful consideration to balance maternal health with fetal safety, as many systemic treatments are unsafe. Topical therapies are generally the first line of defense due to minimal systemic absorption. Emollients and low- to mid-potency topical corticosteroids are considered the safest options. Higher-potency topical steroids should be used sparingly and for the shortest duration possible to minimize systemic effects.
If topical treatments are insufficient, phototherapy using narrowband ultraviolet B (UVB) light is a safe alternative for moderate-to-severe disease. However, UVB can deplete folic acid levels, which is a concern during pregnancy. Therefore, a folic acid supplement is recommended when undergoing this therapy. Systemic medications carry the highest risk and must be approached with caution.
Treatments like methotrexate and oral retinoids (such as acitretin and tazarotene) are strictly contraindicated because they cause severe birth defects and must be stopped well in advance of conception. Some biologic drugs, particularly certolizumab pegol, are often preferred because they are engineered to minimally cross the placenta. This decision requires careful consultation between the patient, dermatologist, and obstetrician.
Fetal Risk and Genetic Predisposition
The presence of psoriasis in the mother does not automatically mean the baby will be harmed, but uncontrolled disease and certain medications pose risks. The disease itself is not associated with an increased chance of birth defects. However, women with moderate-to-severe psoriasis may have a slightly higher risk of adverse outcomes, such as low birth weight, which is often linked to underlying systemic inflammation.
The condition has a strong genetic component, but it is not directly inherited like a simple trait. If one parent has psoriasis, the child has an approximate 15% risk of developing the condition. This risk increases to about 75% if both parents are affected. Psoriasis requires both the genetic predisposition and an environmental trigger, such as a major infection or stress, to manifest. The primary risk to the fetus is typically from the use of unsafe medications or complications associated with poorly managed, severe inflammatory disease.