What are pruritic urticarial papules and plaques of pregnancy?

Every pregnancy experience is different, whether it’s comparing your current pregnancy to your previous one or to someone else's. Whether it's morning sickness, mood swings, fatigue or changes in skin, there's no predicting what body changes you’ll experience, but when it's something unfamiliar, uncommon, or unusual to look at, it's understandable to feel nervous.

Pruritic urticarial papules and plaques of pregnancy (PUPPP) or polymorphic eruption of pregnancy (PEP) relate to the same rash. They affect 1 in 160 pregnancies and are a common reason for skin changes during pregnancy.²

We can break the terms down to understand them better.

Pruritic - itchiness
Urticarial - raised rash
Papules - raised spots or pimples
Plaques - raised, flat-topped and larger than a pimple
Polymorphic - presents in different forms, shapes, sizes

PUPPP is a harmless, itchy, raised rash, often forming around stretch marks, that can look different on different individuals. It is not harmful and does not cause changes in your blood tests. PUPPP is most likely present in women who are pregnant for the first time and who are around 35-39 weeks into their pregnancy. The good news, however, is that there is no correlation to suggest it will affect any of your later pregnancies, too.¹

Causes of PUPPP

The exact reason why PUPPP occurs is still unknown, although there are a few theories, such as the stretching of the skin around the stomach, changes in hormones, or the baby's DNA and placenta having an effect on your skin. 

During pregnancy, the skin stretches at a fast rate, even faster if you’re having twins or triplets. As the skin stretches, lower layers under the skin are damaged because they can’t keep up with the rate of growth. Furthermore, the protein that sits on top of the collagen in your skin could trigger a reaction in the body, similar to that of an allergic reaction, resulting in visual changes in the skin. 

It has also been found out that the cells of the baby can travel from the womb to the mum's skin, but only for baby boys. Some women who had PUPPP had the baby's DNA in their skin, which suggests that it may play a role in triggering it.³ Why this happens particularly during the third trimester is still unknown.

Another theory involves the high levels of progesterone, which are particularly higher for multiple pregnancies (i.e twins or triplets), which may be triggering changes in the skin.

A reason why PUPPP may not be seen in subsequent pregnancies could be because the immune system knows how to respond to the body changes and, therefore, can prevent the repeated onset of PUPPP.¹

Risk factors

• 0.5% if carrying 1 baby
• Approx. 9.5% if carrying twins
• Approx. 15.5% if carrying triplets
• Mostly seen in first pregnancies
• Increased weight gain
• Higher baby weight
• Being caucasian
• You’re having a baby boy
• Greater chance if conceived via IVF 
• Rh protein found on red blood cells (known through a blood test)

You are NOT at any increased risk of having PUPPP rash if:

• You have close family members who have had it
• You have other low-immune-system conditions 
• You have specific protein markers on your cells

What can I do if I have PUPPP?

Treatment for PUPPP is focused on managing the symptoms:

• Antihistamines can help with itchiness
• A cool bath or soothing preparations like aloe vera or calamine cream can cool the skin down, helping with the redness and itchiness
• You may be prescribed a short course of steroids to either apply or take, depending on the severity of your symptoms
• Wearing light cotton clothing can prevent irritation 

How does PUPPP spread?

Other rashes that may look similar to PUPPP

Atopic eruption of pregnancy (AEP)⁵

This is an umbrella term that groups together:

1. Eczema that is either new or previously diagnosed
2. Prurigo of pregnancy - severely itchy spots
3. Pruritic folliculitis - when the hair follicles become inflamed, looking red, raised and causing itchiness

It can be seen as a sudden arrival of bumps on the skin, looking similar to eczema, affecting women who have either a personal or family history of eczema. It clears up on its own after the baby has been born; however, unlike PUPPP, it may recur during future pregnancies. The cause of AEP is assumed to be due to changes in the immune system during pregnancy. 

Pemphigoid gestationis (PG)⁵

This is a rare condition, often occurring during the third trimester. Unlike PUPPP and AEP, this does not resolve at delivery, but rather gets worse initially before getting better over the next few weeks, sometimes months. 

The rash is extremely itchy and looks similar to PUPPP; however, it is caused by the body's overreaction to itself, also known as an autoimmune disorder. Another differentiating factor between PUPPP and PG is that PG does affect the baby, being connected to early birth and babies being underweight. Moreover, the baby may also have a mild version of the rash due to transfer from the placenta.

Remember - don’t ever try to diagnose a rash by yourself. If you’ve got changes to your skin, speak to your doctor or midwife as soon as you can to make sure your diagnosis is accurate, and your treatment is correct.

Why is it more likely to happen in the 3rd trimester?

The baby is constantly growing, and in the third trimester, this is at a much faster rate, especially as you near the end of your pregnancy, after the 35th week. Similarly, if you’re having twins or triplets, you’ll be getting much bigger than you would with a single baby, because your body is making space to carry two growing babies. These are the reasons why PUPPP is more likely to occur in your third trimester - due to your skin stretching significantly more than it does in your earlier stages of pregnancy.

Can PUPPP occur at other points in pregnancy?

PUPPP most commonly occurs in the third trimester and sometimes, in a smaller group of women, immediately after giving birth, affecting just 15%.⁴ Less commonly, PUPPP may present at earlier points in your pregnancy, especially if your body is changing and growing faster. This may affect whether it is initially diagnosed as PUPPP, but if you have a rash, don’t hesitate to see your doctor or midwife to diagnose it accurately.

Summary

Whilst more research is needed to find out exactly what causes PUPPP, and why it only affects some women, remember these 3 things:

1. If you have a rash that is worrying you, see your doctor as soon as possible
2. PUPPP is common, and symptoms can be controlled 
3. It is NOT harmful to your baby¹