Gab Kovacs1 and Paula Briggs2
(1)
Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
(2)
Sexual and Reproductive Health, Southport and Ormskirk Hospital, Southport, UK
Thyroid Disease
Definition
Incidence
Aetilogy and Pathogenesis
Clinical Assessment
Treatment
Complications
Prognosis
Diabetes
Definition
Incidence
Aetilogy and Pathogenesis
Clinical Assessment
Treatment
Complications
Prognosis
Thyroid Disease
Definition
Overt hypothyroidism is defined as a raised TSH level in association with a decreased level of free T4.
Subclinical hypothyroidism is diagnosed when the TSH level is elevated, but T4 is still within the normal range.
Incidence
Overt hypothyroidism is estimated in 0.3–0.5 % of women, and subclinical hypothyroidism in 2–3 % of pregnant women.
Aetilogy and Pathogenesis
The thyroid gland has an important function in maintaining a viable pregnancy and in contributing to the development of a healthy offspring.
There are increased requirements for T4 in pregnancy, and the foetus is totally dependent on the placenta to provide thyroxine until about 18 weeks gestation.
The structure of HCG is similar to TSH and provides some stimulation to T4 production. This results in TSH being suppressed by the negative feedback, eventually resulting in a decrease of T4.
In general, iodine deficiency is the commonest cause of thyroid insufficiency worldwide. The second commonest cause is auto-immune thyroiditis (Hashimotos’s disease).
Clinical Assessment
History
Women with overt hypothyroidism often suffer from subfertility. Women with subclinical hypothyroidism are generally asymptomatic.
Examination
A goitre (enlarged thyroid gland) may be present.
Investigations
Thyroid function tests – TSH, T4, and thyroid antibodies can be measured in a sample of blood. Routine screening in the first trimester is not recommended. However, women with a family history of thyroid disease or other auto-immune diseases should be offered screening. Women living in iodine deficient areas or with a BMI > 40, should also be screened.
Treatment
Medical
· It is recommended that women who are pregnant, planning a pregnancy or are breast feeding should receive 150 μg of iodine daily
· Women with subclinical hypothyroidism, should be treated with thyroxine, if the TSH is > 10 mIU/l
· Women with subclinical hypothyroidism, but positive thyroid auto antibodies should also be treated with thyroxine
· Women with overt hypothyroidism should be treated with thyroxine
· Women who are on thyroid replacement therapy pre pregnancy will often need to increase the dose of thyroxine being taken
Surgical
If at all possible, thyroid surgery is not undertaken during pregnancy.
Complications
Hypothyroidism is associated with an increased risk of EPL, hypertension, preeclampsia, placental abruption, anaemia and PPH. There are also adverse outcomes for the neonate including prematurity, low birth weight, increased perinatal morbidity and mortality, and cognitive and developmental impairment.
Prognosis
Appropriately treated hypothyroidism avoids any of the complications discussed above.
Diabetes
Definition
Gestational diabetes mellitus (GDM) – diabetes that develops during pregnancy. This is diagnosed using a 2 h 75 g oral Glucose Tolerance Test (OGTT). Gestational diabetes can be diagnosed if the fasting glucose is > 5.1 mmol/l, or the level 2 h after the glucose challenge is > 8.5 mmol/l.
Incidence
Approximately 5 % of women have diabetes during pregnancy. Nearly 90 % have gestational diabetes and the remainder have either Type 1 or Type 2 diabetes.
Aetilogy and Pathogenesis
Predisposing factors include obesity, and GDM in a previous pregnancy. Raised blood sugars predispose to macrosomia in the foetus.
Clinical Assessment
History
Assess for risk factors as described above
Examination
BP, BMI, and urinalysis
Investigations
It is recommended that screening for GDM should take place at 26–28 weeks gestation (OGTT).
Treatment
The care of women with gestational diabetes should be provided by a specialist team.
Medical
· Dietary advice with regular blood glucose monitoring
· Insulin may be needed if blood glucose levels are not controlled by diet alone
· Oral hypoglycaemics are not used in pregnancy
Surgical
Plan elective induction or caesarian section for type 1 and 2 diabetics between 37 and 39 weeks
For women with GDM, deliver by the due date
Complications
EPL, preeclampsia, preterm labour, macrosomia, birth injury, stillbirth and perinatal mortality are more common in women with diabetes. In women with preexisting disease, congenital abnormalities are increased.
Prognosis
An OGTT should be undertaken 6–12 weeks after delivery in all women with GDM. Most women with GDM will return to normal glucose metabolism following the birth. These should be advised regarding diet, weight control and exercise. However some will develop Type 2 diabetes.
Well controlled GDM reduces the risks to the mother and the baby.