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[8 min read] A practical approach to pregnant patients presenting with skin rash in a primary care setting

For many women, pregnancy can mean lots of changes in their bodies. Fluctuating hormones and growing bellies can cause pregnancy dermatoses. It’s important to know which of these dermatoses may be dangerous, especially to both mum and baby. Because general dermatology may not always be readily available in remote regions, primary care doctors have an important role to play in the recognition and management of pregnancy dermatoses.

By far the most common pregnancy-related rash is a condition known as atopic eruption of pregnancy. This condition is eczema triggered by pregnancy, though many patients do not have any history of eczema in the past. Atopic eruption of pregnancy occurs in 1 in 5 women. It is thought to be caused by the shift towards Th2 mediated cytokine in pregnancy.

Though atopic eruption of pregnancy is fairly benign for both mum and baby, it can be very itchy and distressing to patients. These patients present eczematous plaques on flexural surfaces of the body, often on a background of xerotic skin. About a third of patients may present with a papular variant.  This rash tends to recur in women during subsequent pregnancies.

The next most common pregnancy dermatosis is a condition called polymorphic eruption of pregnancy, also known as toxic erythema of pregnancy. This is also fairly common, affecting 1 in 160 deliveries. The cause is unknown, but generally benign for both mum and baby as well.

Polymorphic eruption of pregnancy presents with itchy, oedematous pink papules or raised plaques. The rash favours the abdominal stretchmarks, but can spread in just a few days all over the body. The rash can evolve into multiple morphologies, including redness, vesicles, and eczematous-appearing plaques. These skin lesions generally being late in pregnancy and spontaneously resolve over 4 weeks.

A rare but more dangerous pregnancy-related dermatosis is pemphigoid gestationis, also known as herpes gestationis. This condition is rare and may be correlated to HLA-DR3 and HLA-DR4 genotypes. The condition is caused by the same autoantibody as bullous pemphigoid and can be detected via serum testing.

Patients can develop pemphigoid gestationis at any point of pregnancy, and sometimes, during the immediate postpartum period. Lesions tend to start at the umbilicus and spread to itchy wheals and plaques with clustered vesicles or bullae. Though the vesicular rash may appear much like herpes, hence the namesake, the condition is not related to herpes simplex virus.

In most patients with pemphigoid gestationis, skin lesions resolve spontaneously, but may take months following delivery. Rarely, patients have a prolonged rash. Some women may get subsequent flares during periods or on oral contraceptives.

Pemphigoid gestationis is associated with an increased risk of premature birth and small for gestational age newborns. Oftentimes, the risk is correlated to disease severity in the mother. Diagnosis is best made with a skin biopsy with direct immunofluorescence done by a specialist. If pemphigoid gestationis is suspected, it’s best to refer to a dermatologist for skin biopsy and special testing.

Worth mentioning within the realm of pregnancy dermatoses is a condition called intrahepatic cholestasis of pregnancy. These women present with sudden onset intense itch without skin findings, though some patients who have suffered for some time may present with secondary changes such as excoriation or prurigo nodules from scratching. Intrahepatic cholestasis of pregnancy is dangerous to the foetus and can be diagnosed by serum bile acids of more than 3-100x normal levels. Any pregnant woman who presents with an intense itch should be ruled out of this dangerous condition.

For most pregnant women with either atopic eruption of pregnancy or even mild polymorphic eruption of pregnancy, there is no risk to the baby. These women can usually be treated symptomatically with topical steroids and antihistamines. Of course, it is up to the discretion of the general practitioner to use pregnancy-appropriate prescriptions available in their respective country, and caution should be used when prescribing potent topical corticosteroids. In general, pregnant women should avoid high potency due to the risk of growth restriction in the foetus.

In a primary care setting, the most important approach to a pregnant patient presenting with skin rash is to ensure that the patient does not have intrahepatic cholestasis or pemphigoid gestationis. These pregnancy dermatoses may be harmful to the foetus.  Some clues for pemphigoid gestationis include a rash involving the umbilicus and a presentation erupting late in pregnancy. Any pregnant woman with an itch out of proportion to the exam should have serum bile acids evaluated at the very least. If there is any doubt about the diagnosis, the patient should be referred to general dermatology for skin biopsy and further testing. Additionally, other dermatoses unrelated to pregnancy, such as scabies, drug rashes, or viral exanthems, must be ruled out as well.

Sources: Ambros-Rudolph CM. Pregnancy dermatoses. In: Dermatology. 4th ed. Philadelphia, PA: Elsevier Saunders; 2012:472-480.

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