Having thyroid disease does not automatically mean you need more pregnancy ultrasounds. In many pregnancies, routine scans are offered at about 11–14 weeks and again at 18–22 weeks, although timing varies by country and clinic. Extra scans may be recommended if thyroid disease is not well controlled or if Graves’ disease antibodies could affect the baby. Thyroid blood tests—not ultrasound—are usually used to track your hormone levels.
Does thyroid disease change the usual pregnancy ultrasound schedule?
For many pregnant women with thyroid disease, the usual schedule of prenatal ultrasounds remains appropriate. The need for additional scans depends on the specific thyroid condition, how well it is controlled, the results of relevant blood tests, and any other pregnancy-related concerns. A diagnosis of hypothyroidism alone, for example, does not automatically mean that extra fetal ultrasounds are necessary.
As a general example, the National Health Service (NHS) in England offers two routine ultrasound scans: one at 11–14 weeks and another at 18–21 weeks. Other countries and healthcare systems may use slightly different schedules. Your maternity team will advise you about the appropriate timing based on your pregnancy and local prenatal care recommendations.
Which ultrasounds are usually performed during pregnancy?
The first-trimester ultrasound
The first routine scan is commonly performed between 11 and 14 weeks of pregnancy, depending on the healthcare system. It helps estimate how far along the pregnancy is, establish the expected due date, check the number of babies, and assess early development. Where offered, it may also form part of screening for certain chromosome conditions.
Having hypothyroidism or Hashimoto’s thyroiditis does not automatically change the timing of this scan. Your clinician may recommend an earlier ultrasound if there is another reason to confirm the location or progress of the pregnancy, determine gestational age, or investigate a specific concern.
The second-trimester anatomy scan
The second routine scan is often performed between 18 and 22 weeks, although the exact window varies between healthcare systems. It is commonly called the anatomy scan, anomaly scan, or mid-pregnancy scan. During this examination, the sonographer evaluates the baby's physical development and checks structures such as the brain, spine, heart, abdomen, kidneys, and limbs. The scan also assesses factors such as placental location and, when possible, amniotic fluid.
Thyroid disease does not automatically change the timing of this examination. However, if your medical history, thyroid test results, or pregnancy course raises a specific concern, your doctor may arrange additional assessments or a more detailed ultrasound examination.
When might additional pregnancy ultrasounds be needed?
Additional scans are not necessary for everyone with thyroid disease. They may be recommended when there is a concern about the baby's growth or well-being, when maternal hyperthyroidism is not adequately controlled, or when certain thyroid antibodies could affect the baby's thyroid gland. The decision is based on your clinical situation rather than on the thyroid diagnosis alone.
Graves’ disease and thyroid antibodies
Graves’ disease is an autoimmune condition that can cause an overactive thyroid. It is particularly relevant during pregnancy because thyroid-stimulating receptor antibodies, including thyroid-stimulating immunoglobulins (TSI), can cross the placenta and affect the baby's thyroid. These antibodies may remain elevated even after a woman has received treatment for Graves’ disease, including thyroid surgery or radioactive iodine treatment in the past.
The American Thyroid Association's 2026 guidelines for thyroid disease in pregnancy recommend monitoring for fetal and newborn hyperthyroidism when maternal TSH-receptor antibody (TRAb) or TSI levels are above three times the upper limit of normal. In these circumstances, the healthcare team may arrange additional fetal assessments, including ultrasound examinations, to evaluate the baby's heart rate, growth, amniotic fluid, and thyroid size. The timing and frequency of these scans are individualized.
A history of Graves’ disease should therefore be discussed with your obstetrician early in pregnancy, even if the thyroid condition is currently in remission or you no longer take antithyroid medication. The need for extra scans depends on factors such as antibody levels, thyroid function, medication use, and findings from earlier assessments.
Uncontrolled hyperthyroidism
Hyperthyroidism means that the thyroid gland produces too much thyroid hormone. When it is not adequately controlled, it can be associated with pregnancy complications and may affect fetal growth or heart rate. In selected cases, the obstetric team may recommend repeated ultrasound examinations to assess the baby's development and look for signs of fetal thyroid dysfunction.
The American Thyroid Association's patient guidance on hyperthyroidism in pregnancy explains that Graves’-related antibodies can affect the baby's thyroid and that appropriate maternal monitoring helps identify pregnancies requiring closer follow-up. Not every woman with hyperthyroidism needs serial fetal ultrasounds; the decision depends on thyroid control, antibody results, treatment, and other clinical findings.
Other reasons for closer ultrasound monitoring
A pregnant woman with thyroid disease may also need additional scans if a separate obstetric concern develops. These concerns can include suspected poor fetal growth, abnormal findings on a previous scan, or another medical or pregnancy-related condition that warrants closer monitoring. In such cases, ultrasound timing is determined by the particular concern and the clinician's assessment, not simply by the presence of thyroid disease.
Is a thyroid ultrasound the same as a pregnancy ultrasound?
No. A pregnancy ultrasound examines the baby and the uterus, while a thyroid ultrasound examines the thyroid gland in the front of the neck. These tests have different purposes and are not interchangeable.
A thyroid ultrasound may be ordered during pregnancy if a clinician finds a thyroid lump, suspects a thyroid nodule, or needs to assess a structural change in the gland. The 2026 American Thyroid Association guidelines identify thyroid ultrasound as an important tool for evaluating a thyroid nodule during pregnancy. There is no standard pregnancy week for this examination; its timing depends on why it is needed.
Thyroid ultrasound does not measure hormone levels, and it is not used to determine whether hypothyroidism or hyperthyroidism is adequately controlled. These questions are assessed mainly through blood tests and clinical evaluation. In addition, ultrasound of the mother's thyroid is not generally used to distinguish Graves’ disease from temporary thyroid changes associated with pregnancy.
How is thyroid disease monitored between ultrasound scans?
Ultrasound and thyroid function tests provide different types of information. A fetal scan evaluates the baby's anatomy and development, while blood tests measure thyroid function and, when indicated, antibodies that may affect the pregnancy. A reassuring ultrasound does not establish that maternal thyroid hormone levels are normal, so blood-test follow-up remains important even when routine scans are normal.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), women with thyroid problems should have regular thyroid function testing during pregnancy and take medicines prescribed by their healthcare professional. The frequency of testing varies with the condition, treatment, trimester, and previous results. Women taking thyroid medication may need adjustments as pregnancy progresses.
For this reason, keep your prenatal appointments even if an ultrasound shows normal development. Your obstetrician or endocrinologist may need to review thyroid-stimulating hormone (TSH), free thyroxine (free T4), and, in selected cases, TRAb or TSI levels to decide whether your current monitoring plan remains appropriate.
What should you tell your doctor before a pregnancy ultrasound?
Before your scan, let your maternity team know which thyroid condition you have, whether it is currently controlled, and which medicines you take. Also mention any previous Graves’ disease treatment, including thyroid surgery or radioactive iodine, and share any available antibody test results. This information helps the team decide whether routine pregnancy scans are sufficient or whether additional fetal monitoring may be appropriate.
If you are newly pregnant and have a known thyroid condition, contact your prenatal care team early rather than waiting for the first scheduled ultrasound. They can arrange the necessary blood tests, review your treatment, and plan pregnancy imaging according to your individual needs. Do not stop or change prescribed thyroid medication without discussing it with your healthcare professional.
What is the main takeaway about ultrasound timing?
For most pregnant women with thyroid disease, the usual first-trimester and mid-pregnancy scans remain the starting point. Extra ultrasounds may be appropriate for selected women, particularly those with Graves’ disease and significantly elevated thyroid antibodies, poorly controlled hyperthyroidism, or additional pregnancy-related concerns. There is no single additional scan week that applies to everyone. Your obstetrician and thyroid specialist can determine the schedule that best fits your test results and pregnancy.