Neonatal Outcomes of Mothers with Hypothyroidism in the Third Trimester

Aims: To determine the relationship between maternal hypothyroidism and preterm birth, neonatal low birth weight and neonatal thyroid stimulating hormone (TSH) levels.

Study Design: Cross-sectional study.

Place and Duration of Study: Department of Obstetrics and Gynaecology in a tertiary hospital in Rivers State, Southern Nigeria from June 2014 to November 2014.

Methodology: Serum TSH and free thyroxine (FT4) were analyzed in pregnant women before delivery and cord blood TSH was analyzed in their babies immediately after delivery. Maternal hypothyroidism was defined as serum TSH > 3.0 mIU/L in the third trimester according to the American Thyroid Association (ATA) recommendation.

Results: Out of 168 pregnant women, 25 (14.9%) women had subclinical hypothyroidism. None had overt hypothyroidism. They had babies with lower birth weight (P = .037) and lower Apgar scores at 1 minute (P = .003) and 5 minutes (P = .001) compared to mothers without hypothyroidism. A total of 17 (10%) babies had low birth weight. Fourteen (8.3%) babies were preterm. Thirteen (7.7%) babies were admitted into the neonatal intensive care unit (NICU) and among them babies born to mothers with hypothyroidism had a higher frequency of admission into NICU (P = .002), lower gestational age (P = .006) and higher mean TSH (P = .015) than babies born to mothers without hypothyroidism.

Conclusion: Maternal subclinical hypothyroidism was associated with neonatal low birth weight, low Apgar scores, preterm birth and high neonatal TSH. Timely detection and treatment of maternal hypothyroidism could reduce the burden of adverse neonatal outcomes.