In the first 12 weeks, the baby's brain development depends heavily on the mother's T4. The fetal thyroid is not yet ready to make enough hormone on its own, so maternal hypothyroidism during this window can affect early neurodevelopment if it is missed or undertreated.

Poorly controlled hypothyroidism in pregnancy is linked with miscarriage, preterm birth, hypertensive complications, and lower child IQ in some studies. It also overlaps with other pregnancy risks such as preeclampsia and high BP, which is one reason thyroid control is treated as core antenatal care rather than an optional extra.

For pregnancy, commonly used ITSI and ATA style targets are stricter than non-pregnant ranges. First trimester target TSH is 0.1 to 2.5 mIU/L. Second trimester target is 0.2 to 3.0 mIU/L. Third trimester target is 0.3 to 3.0 mIU/L.

A simple India-friendly rule is this: keep TSH below 2.5 in trimester 1, then below 3.0 in trimesters 2 and 3. If you are planning pregnancy or have thyroid disease already, thyroid and fertility is a useful companion read because the target tightens even before symptoms change.

Indian guidance has leaned toward universal pregnancy thyroid screening because prevalence is high. ITSI and FOGSI 2017 support testing all pregnant women at the first antenatal visit, instead of waiting only for symptoms or family history.

This matters because hypothyroidism in Indian pregnancy is often estimated around 12 to 15 percent, and many women feel normal or only mildly tired. If the first trimester result is borderline, especially near the upper limit, many clinicians recheck monthly until the pattern is clear.

If you already have hypothyroidism and become pregnant, the usual advice is to increase levothyroxine by about 30 percent as soon as pregnancy is confirmed. Do not wait several weeks for the next OB visit if you were already on treatment and have clear prior instructions from your doctor.

For a new diagnosis in pregnancy, starting doses are often around 1.6 to 2 mcg per kg per day, then adjusted using TSH follow-up. The exact dose depends on weight, baseline TSH, free T4, symptoms, and whether the diagnosis is overt or subclinical.

Levothyroxine brands commonly used in India include Eltroxin and Thyronorm. Take the tablet on an empty stomach, ideally 30 to 60 minutes before breakfast, with water only. Consistency matters more than perfection, so choose a routine you can follow daily.

Avoid chai, coffee, calcium, and iron close to the dose because they reduce absorption. Leave at least 4 hours between levothyroxine and iron or calcium tablets. This is especially important if you are also treating anemia in pregnancy, because iron and thyroid tablets are often prescribed together.

TSH is usually checked every 4 weeks in the first and second trimesters because requirements can change quickly. In the third trimester, monitoring often shifts to every 6 to 8 weeks if results have been stable and symptoms are quiet.

After delivery, repeat TSH around 6 weeks postpartum to reassess the dose. Many clinicians also check ferritin and iron once in trimester 1, because iron deficiency can coexist and complicate fatigue. If hyperthyroid symptoms are suspected, free T4 becomes important in addition to TSH.

A TSH test in private Indian labs such as Dr Lal PathLabs or Metropolis often costs about Rs 150 to Rs 400. Government facilities and some PHCs may offer testing free or at very low cost, though turnaround time varies by location.

Levothyroxine is usually affordable. Eltroxin and Thyronorm often cost about Rs 50 to Rs 200 per month, Thyrox about Rs 100 to Rs 300, and home sample collection may add roughly Rs 100 to Rs 300. Endocrinology or specialist OB follow-up in larger centres such as Apollo or AIIMS can range roughly from Rs 800 to Rs 3000.

Subclinical hypothyroidism usually means TSH is between 2.5 and 10 mIU/L while T4 remains normal. In pregnancy, treatment is more likely to be advised if TPO antibodies are positive, if there is a history of miscarriage, or if conception happened through IVF.

This is one area where guidance can feel mixed. ICMR-oriented practice is often more conservative, while ATA-style practice can be more aggressive. The decision should sit in the context of your trimester, prior losses, fertility history, and other pregnancy risks such as gestational diabetes in India.

Not every thyroid problem in pregnancy is hypothyroidism. Graves disease can cause hyperthyroidism, and treatment differs by trimester. PTU, or propylthiouracil, is generally preferred in trimester 1, while methimazole is commonly preferred in trimesters 2 and 3.

Thyroid storm is rare but is a true emergency with fever, severe palpitations, agitation, or heart failure features. Radioactive iodine 131 is contraindicated in pregnancy and must be avoided. Specialist follow-up is important because overtreatment can also affect fetal growth.

Around 10 percent of women may develop postpartum thyroiditis, and it is often missed because its symptoms overlap with new-parent exhaustion. A temporary hyperthyroid phase can come first, followed later by a hypothyroid phase over 6 to 12 months.

If fatigue, low mood, palpitations, or unexplained weight change continue beyond the expected early postpartum period, ask for TSH testing. A check is especially reasonable if symptoms persist past 3 months or if you needed thyroid treatment during pregnancy.