Treatment of psoriasis in pregnancy

Author: Dr Amanda Oakley, Waikato Hospital, Hamilton, New Zealand, 2008.

Pregnant women with psoriasis need to be aware that some treatments for psoriasis may harm their baby. The effect of many treatments is unknown, and for others the threshold for harm is unknown. A summary of relevant known hazards in pregnancy is included here. Seek your doctor's advice.

About 2% of all pregnancies result in serious congenital malformations noted at birth and another 3% of babies are found to have malformations at a later date. They occur mostly for unknown or genetic reasons. Very few are caused by medications; these medications are said to be teratogenic.

Medical problems such as diabetes, obesity or hypertension, which are common in patients with psoriasis (metabolic syndrome), may also lead to complications in pregnancy.

Pregnancy category

Medicines have been assigned pregnancy categories depending on the assessed risk of fetal injury due to the medicine. The categories may vary from country to country, and medicines may be assessed as having different risks in each country. Not all medicines have been assessed.

The Australian Drug Evaluation Committee's (ADEC) system is used in New Zealand.

ADEC Pregnancy Categories
A Drugs which have been taken by a large number of pregnant women and women of childbearing age without an increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
B1 Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have not shown evidence of an increased occurrence of fetal damage.
B2 Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.
B3 Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans.
C Drugs which, owing to their pharmaceutical effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible.
D Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects.
X Drugs that have such a high risk of causing permanent damage to the fetus that they should NOT be used in pregnancy or when there is a possibility of pregnancy.

Topical therapies

A small amount of medication applied to a small area for a short time is not likely to be harmful. A large amount to a large area for a long time increases the risk of harm, especially if covered by occlusive dressings.

Topical therapies for psoriasis in pregnancy
Emollients Simple emollients appear safe to use in pregnancy.
Salicylic acid Absorbed through the skin (10-25%). Oral salicylates have been associated with bleeding and harm to the baby but the risk with topical therapy is considered very small. Do not apply over large areas of the body for prolonged periods.
Coal tar The risk of absorption and injury to the baby is unknown but coal tar contains potentially hazardous polycyclic aromatic hydrocarbons. Coal tar products are considered safe if used for short periods or on localised areas such as the scalp.
Dithranol / anthralin The risk in pregnancy is unknown but the drug is probably not absorbed through the skin.
Topical corticosteroids Category A, except mometasone (B3) and methylprednisolone aceptonate (C). Small amounts of low potency products appears safe. Do not use large amounts of potent products over large areas of the body for more than a few days.
Calcipotriol Category B1. Risk in pregnancy is unknown. Maximal adult dose is 100g/week, with 6% systemic absorption. Ensure dose is kept under this amount. If breastfeeding, do not apply to chest area.
Calcineurin inhibitors (tacrolimus ointment, pimecrolimus cream) The risk is unknown. Low absorption through the skin. Oral tacrolimus is Category C.

Phototherapy

Photherapy with broadband UVB and narrowband UVB appears as safe in pregnancy as at other times.

Photochemotherapy (psoralens and UVA or PUVA) is effective partly because it damages cellular DNA, so it is thought safest to avoid oral PUVA during pregnancy. However, no specific damage to mother or child has been reported. Methoxsalen is Category B2. The risk of topical PUVA in pregnancy is considered very low.

Systemic therapy

Most antipsoriatic systemic medications should be avoided in pregnancy. Some are known teratogens, i.e., cause birth deformities in a greater number of babies that the normal background rate.

Systemic therapies for psoriasis in pregnancy
Methotrexate Category D. Must be avoided in pregnancy and for at least three months after the last tablet has been taken. Serious risk of fetal malformation of head, face, limbs with developmental delays. Critical period is 6 to 8 weeks post conception, if a dose of greater than 10 mg once weekly is taken. May increase the risk of miscarriage. Do not breastfeed while taking methotrexate.
Acitretin Category X. Must be avoided in pregnancy during treatment or for at least two years after the last capsule has been taken; persistent circulating drug more likely if alcohol is taken. Serious risk of fetal malformation of brain, ears, face, heart, thymus, central nervous system and limbs. Do not breastfeed while taking acitretin.
Ciclosporin Category C. Risk of fetal malformation is similar to that of untreated woman. But may cause high blood pressure and kidney damage, which might harm the baby. If treatment is essential, it must be monitored carefully. It is best not to breast feed during treatment as ciclosporin passes into the milk.
Hydroxyurea Category D. Must be avoided in pregnancy. Serious risk of fetal malformation. Women taking hydroxyurea should not breastfeed.
Mycophenolate mofetil Category D. Must be avoided in pregnancy. Serious risk of fetal malformation of ear, face, heart, eye, limb and other organs. It is best not to breast feed during treatment as mycophenolate may pass into the milk.
Biologic response mediators Category C. Very little information is available so the risk is unknown at this time. Therefore, biologics should be avoided during pregnancy and breast feeding.

What treatment is safe to use in pregnancy?

The appropriate treatment for psoriasis in a woman who is pregnant, or who plans pregnancy, will depend on the extent and severity of the skin condition.

Topical therapy can be used with confidence, but avoid using large quantities of salicylic acid, calcipotriol, topical steroids and calcineurin inhibitors for long periods of time.

UVB phototherapy is safe for pregnant women with more severe psoriasis. Ciclosporin can be prescribed when systemic therapy is essential, providing blood pressure and kidney function are very carefully monitored.

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