Publication:

A study on the effect of exogenous thyroxine on known hypothyroid and the newly diagnosed hypothyroid patients during first trimester of pregnancy

Background Hypothyroidism complicates pregnancy and is associated with adverse maternal and fetal outcomes if inadequately treated. This study evaluated the effect of levothyroxine on thyroid function and pregnancy outcomes among women with known and newly diagnosed hypothyroidism during the first trimester.

Methods A prospective observational study was conducted in an Obstetrics and Gynaecology department from September 2024 to October 2025. Fifty pregnant women diagnosed with hypothyroidism in the first trimester (25 known, 25 newly diagnosed) were enrolled via consecutive sampling. Thyroid function tests (TSH, free T3, free T4) were assessed at baseline, six weeks post-intervention, and during the second and third trimesters. Maternal complications, delivery mode, neonatal outcomes, and NICU admissions were recorded.

Results Participants' mean age was 24.30±3.04 years. Subclinical hypothyroidism was present in 54% (n=27) and overt hypothyroidism in 46% (n=23). Women with overt hypothyroidism had significantly higher TSH and lower free T3 and free T4 levels throughout pregnancy compared to those with subclinical hypothyroidism (p=0.001). Dose adjustments were required in 92% of women at baseline, decreasing to 68% by the third trimester. Term normal vaginal deliveries occurred in 90% of women, while 10% underwent caesarean section. Complications included miscarriage (18%), gestational diabetes (12%), gestational hypertension (10%), postpartum haemorrhage (10%), and abruptio placentae (4%). NICU admission was required for 19.5% of live births. Mean birth weight was 2.67±0.23 kg, and mean APGAR score was 8.62±1.12.

Conclusions Early diagnosis, regular monitoring, and timely levothyroxine adjustments improve thyroid control and foster favorable maternal and neonatal outcomes. Continuous surveillance remains essential, particularly for overt cases.