THE RELATIONSHIP BETWEEN MATERNAL IODINE STATUS AND THYROID FUNCTION WITH FOETAL OUTCOME IN ZARIA, NIGERIA

Abstract

Background: Iodine is necessary for the synthesis of thyroid hormones. Normal maternal
thyroid function during pregnancy is critical for normal foetal development.
Objective: The main objective of this study was to relate maternal iodine status and thyroid
function with foetal outcome in pregnant women in Zaria.
Method: Three hundred apparently healthy pregnant and one hundred non pregnant healthy
controls were enrolled for the study. Blood and urine specimens from these volunteers were
collected and analyzed for serum Thyroid stimulating hormone (TSH), Free thyroxine (Free
T4), Free triiodothyronine (Free T3), Thyroid peroxidase antibody (TPO) by Enzyme-Linked
Immunosorbent Assay (ELISA) and urinary iodine concentrations by modified Sandell –
Kolthoff reaction. Cord blood samples from babies of the same pregnant women were
obtained immediately after delivery and analyzed for TSH. Baby’s birth weight, sex,
gestational age at delivery, Apgar score at one minute after delivery, duration of labour, and
method of delivery were all recorded. Statistical analysis was carried out using Epi Info.
Results: Pregnant women and controls were iodine sufficient with median urinary iodine
concentrations of 193 and 205 µg/L respectively. Prevalence of hypothyroidism,
hyperthyroidism and TPO in pregnant women were found to be 3.0, 2.3 and 9.0 %
respectively. Pregnant women with positive TPO antibody were at higher risk of developing
hypothyroidism with odds ratio of 5.56 % (p <0.05). Risk of preterm delivery was higher in
TPO positive mothers with odds ratio of 7.90 %, p<0.001. Maternal hypothyroidism was
associated with fivefold increase in severe foetal birth asphyxia and twofold increase in
preterm deliveries (p>0.05). Cord blood TSH showed no significant relationship with features
of perinatal outcome.

Conclusion: Nigerian women in Zaria were iodine sufficient. The prevalence of maternal
thyroid disorders in this study was not different from those obtained in other iodine sufficient
regions in the world. Maternal hypothyroidism and thyroid autoimmunity were associated
with maternal and foetal complications.
Recommendation: Routine screening of all pregnant women for thyroid disorders during
antenatal care visits may be of benefit even in iodine sufficient areas.

THE RELATIONSHIP BETWEEN MATERNAL IODINE STATUS AND THYROID FUNCTION WITH FOETAL OUTCOME IN ZARIA, NIGERIA