A high index of suspicion is therefore required especially in women at risk of thyroid disease e.g. women with a personal or family history of thyroid disease, goitre, or co-existing primary autoimmune disorder like type 1 diabetes. Risks of hypothyroidism on fetal and maternal well-being
Hypothyroidism is diagnosed by noting a high TSH associated with a subnormal T4 concentration. Subclinical hypothyroidism (SCH) is present when the TSH is high but the T4 level is in the normal range but usually low normal. SCH is the commonest form of hypothyroidism in pregnancy and is usually due to progressive thyroid destruction due to autoimmune thyroid disease.Several studies, mostly retrospective, have shown an association between overt hypothyroidism and adverse fetal and obstetric outcomes (e.g. Glinoer 1991). Maternal complications such as miscarriages, anaemia in pregnancy, pre-eclampsia, abruptio placenta and postpartum haemorrhage can occur in pregnant women with overt hypothyroidism. Also, the offspring of these mothers can have complications such as premature birth, low birth weight and increased neonatal respiratory distress. Similar complications have been reported in mothers with subclinical hypothyroidism. A three-fold risk of placental abruption and a two-fold risk of pre-term delivery were reported in mothers with subclinical hypothyroidism. Another study showed a higher prevalence of subclinical hypothyroidism in women with pre-term delivery (before 32 weeks) compared to matched controls delivering at term. An association with adverse obstetrics outcome has also been demonstrated in pregnant women with thyroid autoimmunity independent of thyroid function.
Postpartum thyroid dysfunction is a destructive thyroiditis with similar pathogenetic features to Hashimotos thyroiditis.The disease is very common with a prevalence of 5-9% of unselected postpartum women. Typically there is a transient hyperthyroid phase that is followed by a phase of hypothyroidism. Permanent hypothyroidism occurs in as much as 30% of cases after 3 years, and in 50% at 7–10 years. The hyperthyroid phase will not usually require treatment but, rarely, propanolol may be used for symptom control in severe cases. The hypothyroid phase should be treated with thyroxine if patients are symptomatic, planning to get pregnant, or if TSH levels are above 10 mU/L. Long-term follow up is necessary due to the risk of permanent hypothyroidism.Nearly all the women with Postpartum thyroid dysfunction have anti-thyroid peroxidase antibodies. This marker can be a useful screening test in early pregnancy as 50% of women with antibodies will develop thyroid dysfunction postpartum. In addition, some but not all studies have shown an association between Postpartum thyroid dysfunction and depression so that thyroid function should be checked postpartum in women with mood changes. == References ==