The normal reference ranges for TSH and T4 (free and total) during pregnancy differ from those in non-pregnant women because of the effects of pregnancy hormones on thyroid function. These test results also change with the trimester of pregnancy and may vary from one laboratory to another due to the analytical methods used to measure TSH and Free T4. Accredited Pathology laboratories will report TSH and Free T4 levels in a pregnant woman according to their locally derived, trimester specific, reference ranges using a specific analytical method. Because comparison of test results between laboratories can be misleading it is wise to always have the tests performed by the same laboratory.
An increase in iodine intake is required during pregnancy from 150 ug daily in the non-pregnant state to 250 ug daily while pregnant. When contemplating pregnancy, during pregnancy and whilst breastfeeding please be aware of the National Health Medical Research Committee’s (NHMRC) recommendation to ingest a daily supplement of 150mcgs of Iodine which will help protect your thyroid health during pregnancy and your foetus’s development. Iodine is essential for both the maternal and foetal thyroid glands to produce T3 and T4. The foetus relies on its mother’s intake of iodine for its development.
The latest research published in The Lancet in March 2022 promotes the importance of the mother’s adequate thyroid health and avoidance of even mild or subclinical hypothyroidism to prevent the risk of gestational hypertension and pre-eclampsia. This recent research emphasises that hypertensive disorders of pregnancy, including gestational hypertension and preeclampsia or eclampsia, affect around 10% of pregnant women and are one of the leading causes of maternal and neonatal mortality and morbidity worldwide and that women suffering hypertension during pregnancy are at increased risk of long-term cardiovascular consequences and hypertensive disorders in subsequent pregnancies, and evidence suggests a risk of reduced cognitive ability in their offspring.
References: Toloza F et al 2022: “Association between maternal thyroid function and risk of gestational hypertension and pre-eclampsia: a systematic review and meta-analysis. Lancet March 4, 2022. Stagnaro-Green A 2022. Commentary: “Thyroid disease in pregnancy: a touch of Clarity”. Thyroid, Vol 32 (4) 2022. Chen J, Zhu J, Huang X, Zhao S, Xiang H, Zhou P, Zhou T, Xu Z 2022 “ Subclinical hypothyroidism with negative for thyroid peroxidase antibodies in pregnancy: Intellectual development of offspring”. Thyroid 32:449–458.
This most recent research in the field of thyroid disorders in pregnancy highlights the importance of early detection and treatment of even mild degrees of hypothyroidism in pregnancy.
Soon after your baby is born, please ensure your newborn is given a Heel Prick Test, which is essential. The Heel Prick Test includes the TSH (Thyroid Stimulating Hormone) test which will determine your newborn’s thyroid health status. This is performed routinely on all newborn babies throughout Australia.
If you are considering pregnancy, or if you are pregnant or breastfeeding, it is important your thyroid function is tested, monitored and treated if necessary and your daily intake of iodine is essential for the brain development of your baby.
Australian research shows 50% of pregnant women are iodine deficient, which can affect the development of the foetal brain and lead to lower intelligence and learning difficulties.
The Australian Thyroid Foundation recommends you take a specifically-formulated daily pregnancy supplement containing at least 150 micrograms of iodine. Also replace the salt you use with iodised salt, to ensure you get adequate iodine in your daily diet.
The Australian Thyroid Foundation also recommends you speak to your doctor about the importance of testing and monitoring your thyroid hormone levels. A healthy Thyroid hormone level is essential for the development of the foetus and sustaining pregnancy.
Latest research states, ADHD and Autism can be a result of iodine deficiency and low thyroid hormone levels in the pregnant women.
Safeguard your pregnancy and baby's development. Speak to your GP or obstetrician about the benefits of Iodine Supplementation and Good Thyroid Health.
The Australian Thyroid Foundation recommends that all women of childbearing years, understand the importance of their thyroid health status when contemplating pregnancy, and while pregnant and breastfeeding.
Determining your thyroid health before you conceive and once your pregnancy is confirmed is essential for your gestational health and the development of your newborn. Ongoing monitoring and treatment if needed should be continued to ensure you and your newborn’s health is protected.
Please speak to your GP and Obstetrician and ask for all the relevant thyroid pathology tests to be ordered before you conceive and once your pregnancy is confirmed. As previously emphasised, blood test results may vary from one laboratory to another so try to stick with the same accredited laboratory for all testing. Ongoing monitoring during pregnancy and treatment should not be overlooked if needed.
Tel: +61 (0) 447 834 724
PO Box 7161
Norwest NSW 2153
The mission of The Australian Thyroid Foundation Ltd (ATF) is to offer support, information and education to members and their families through the many services provided by The ATF and raise awareness about health consequences of iodine deficiency and the benefits of good thyroid health.