The Pregnancy Dermatoses

There are five major dermatoses which occur in pregnancy, and some that can be precipitated by pregnancy.

Pruritus of pregnancy
Itching occurs in about 20 per cent of pregnancies. Sometimes this is in association with an inflammatory dermatosis. Often there are no physical signs, other than scratch marks, and iron deficiency must be excluded. In about 2 per cent of women itching is related to cholestasis of pregnancy, when it is termed pruritus gravidarum. The itching begins in the third trimester and affects the abdomen, palms, and soles. Liver function tests are abnormal and bile salts are raised. It resolves postpartum, but will recur in subsequent pregnancies.

Management consists of emollients and sometimes antihistamines. Chlorpheniramine is the one usually recommended for pregnancy. The non-sedating antihistamines are probably ineffective.

Polymorphic eruption of pregnancy (pruritic urticated papules and plaques of pregnancy)

This dermatosis affects 1 in 240 singleton pregnancies but is more common in multiple births, and is thus being seen more often in the context of in vitro fertilization. It is more common with a male foetus. The dermatosis usually begins in the third trimester and occasionally postpartum. It is most common in first pregnancies or the first multiple pregnancy.

The lesions usually begin in the striae on the abdomen and thighs, and then spread to the whole trunk and limbs, including the hands and feet. The lesions are raised red papules (Plate 1) and plaques, occasionally polycyclic, and rarely may blister on the lower legs. The itching can be very severe, preventing sleep. The histopathology shows oedema, perivascular lymphocytes, and eosinophils. Immunofluorescence does not demonstrate any circulating or bound immunoreactants.

The aetiology is unknown, but there is an association with a low serum cortisol. The increased frequency in multiple births may relate to the mechanical effect of the abdominal stretching or to an increased immune complex load.

Treatment is with reassurance and emollients, for example aqueous cream and 1 to 2 per cent menthol, is helpful, but is not always sufficient. Antihistamines and moderate to very potent topical steroids, which will have significant absorption (see Table 1), and occasionally systemic steroids or induction, may be required. The condition resolves over days to weeks after delivery. It does not usually recur. The outcome of the pregnancy is not adversely affected.

Prurigo of pregnancy
This is may affect 1 in 300 pregnancies. It commences at the end of the second or beginning of the third trimester. The eruption is scattered over the abdomen and limbs, and comprises excoriated papules. There is intense pruritus. It is essential to make sure that iron deficiency is not a contributing factor.