The short explanation
Thyroid hormone affects ovulation, the regularity of periods and the early weeks of pregnancy. An underactive or overactive thyroid can make ovulation less regular and is linked with a higher chance of miscarriage if left untreated. Checking it before fertility monitoring is routine good practice, not a sign that your doctor suspects a problem. If the test is normal, one possible cause is ruled out. If it is a little off, it is usually simple to manage and doing so can help.
What depends on your situation
The parts of this that change from woman to woman. Uncertainty is stated, not hidden.
- Your doctor may also check prolactin, blood count and other tests at the same time, because these affect cycles too. Your husband's semen test is often done early as well, since causes can be on either side.
- If your TSH is mildly high, your doctor may use a tighter target than for women who are not trying to conceive, and may check TPO antibodies.
- Family pressure to conceive quickly is common. Getting the basic tests done properly first often saves time and money later.
What this answer cannot determine
The boundary of online education. These need a clinician who can see you.
- This answer cannot tell you what your result will be or what it means for your fertility. Your gynaecologist will interpret it alongside your other tests.
Questions for your clinician
Take these with you. You can add any of them to an appointment card.
- What thyroid level do you aim for while I am trying to conceive?
- Do I need TPO antibodies or prolactin checked as well?
- If my thyroid needs treatment, does follicle study need to wait?
- What tests does my husband need?
When to seek help
Clinician-approved guidance for this topic. When in doubt, being seen is never the wrong choice.
Emergency — call 112 now
- Call 112 if you have a positive pregnancy test with severe one-sided abdominal pain, fainting or heavy bleeding.
Book an appointment soon
- See your doctor within a few days if you become pregnant, so your thyroid can be rechecked early.
Raise it at a routine appointment
- Complete the thyroid test before the follicle study as advised and review the results at your routine visit.
Sources
The evidence this explanation is built on.
- Thyroid tests MedlinePlus (NIH)
- Hypothyroidism MedlinePlus (NIH)
- Thyroid disease and pregnancy NIDDK (NIH)
Who wrote and reviewed this
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- Author
- AskHer Editorial (AI-assisted draft) AskHer's editorial team — not an individual clinician Works in English, தமிழ், हिन्दी
- Clinical reviewer
- Nobody yet No clinician has signed this answer off, and no person on the editorial team has read it yet. That is what the “Written with AI assistance” label means. It is queued for an editor to read, and then for a clinician who works in this area. The sources it was drafted against are listed above.
- Review status
- Written with AI assistance — not yet reviewed by a person
- Last reviewed
- Not yet reviewed by a person
- Version
- 1
Correction history
Substantive changes are listed, not quietly edited away.
No corrections have been made since this answer was first published.
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