Impact of Gestational Hypothyroidism on Exclusive Breastfeeding in the Early Postnatal Period

Exclusive breastfeeding (EBF) provides health benefits, yet its continuation remains limited. Maternal endocrine disorders, including gestational hypothyroidism, may impair lactogenesis through hormonal dysregulation; however, evidence regarding the association between gestational hypothyroidism and breastfeeding outcomes remains limited.

To investigate the association between maternal gestational hypothyroidism and breastfeeding outcomes in term infants, with a focus on EBF at the end of the first month and formula-free breast milk feeding at 6 months.

This retrospective matched case-control study compared term infants of mothers with gestational hypothyroidism treated with levothyroxine (n = 103) and matched controls (n = 103). Feeding data were obtained from medical records and 6-month telephone follow-up, and factors associated with early formula supplementation were analyzed using multivariable logistic regression.

EBF rates were significantly lower in the case group at 1 month (58.3% versus 81.6%, p < 0.001). Formula supplementation within the first postnatal day was more frequent in the case group than in controls (46.6% versus 21.4%; χ² = 14.63, p < 0.001). At 6 months, formula feeding-either alone or combined with breastfeeding and/or complementary foods-was significantly more frequent in the case group (45.6% versus 25.2%, p = 0.003). Among infants who ever received formula (n = 84), formula was initiated during the first postnatal month more frequently in the case group (82.7% versus 59.4%, p = 0.018), with earlier mean age at formula initiation (1.4 ± 0.97 versus 2.3 ± 1.51 months, p = 0.003). Multivariable logistic regression showed that higher maternal gravidity was independently associated with early formula supplementation (odds ratio = 3.16; 95% confidence interval: 1.09-9.10; p = 0.033).

Gestational hypothyroidism was associated with lower EBF rates at 1 month and increased early formula supplementation. These findings underscore the need for targeted lactation support and careful postpartum follow-up in mothers with gestational hypothyroidism.