The impact of maternal hypothyroidism during pregnancy on neonatal outcomes: a systematic review and meta-analysis

Abstract

The effects of maternal hypothyroidism on neonatal outcomes were not definitely confirmed. We conduct a systematic review of the literatures on the impact of maternal hypothyroidism on neonatal outcomes. We searched Pubmed, Embase and the Cochrane Controlled Trials Register databases complemented by manual searches in article references without language restrictions published from 1946 to April 2015. Nine trials are included. For preterm birth in pregnancies of hypothyroidism women, there is an increased tendency (RR 1.18; 95% CI 0.99 to 1.40; p = 0.06). The same result is seen relating to the low birth weight (RR 1.31; 95% CI 1.00 to 1.72; p = 0.05). Regarding small for gestational age there is no significant increase. Children who were born from mothers with hypothyroidism during pregnancy have increased birth weight (MD 32.35, 95% CI 7.46 to 57.24; p = 0.01). The impact of maternal hypothyroidism shows a trend of reduced risk of large for gestational age (RR 1.17; 95% CI 0.99 to 1.38; p = 0.06). Our review suggests that mothers with hypothyroidism during pregnancy are more likely to give birth to children with higher birth weight or LGA, and L-T4 supplementation should be recommended. The risk of preterm birth and low birth weight also tends to be higher in children with hypothyroidism mothers.

Effects of fetal hypothyroidism on uterine smooth muscle contraction and structure of offspring rats

“…According to our results, the decreased frequency and amplitude of uterine contractions might also be involved in the increased gestational length; however, given that in the present study the uterine contractions were measured in only the female offspring of hypothyroid mothers and not in the dams themselves, this result should be treated with caution. In contrast to the longer gestational length observed in fetal hypothyroid rats in the present study, the risk of preterm birth is higher in humans with hypothyroidism during pregnancy (Hou et al., ; Krassas et al., ). This might be attributable to differences in thyroid hormone synthesis and metabolism and to differences in the alterations to the binding protein during pregnancy (Choksi, Jahnke, St Hilaire, & Shelby, ).…”

Preconception TSH and pregnancy outcomes: a population‐based cohort study in 184 611 women

“…A major limitation of these studies is that they did not include LGA or macrosomia as major outcomes, possibly because the risk of LGA was not recognized as fully as that of SGA. However, a recent meta‐analysis reported a tendency towards an increased risk of LGA among hypothyroid mothers (RR (relative risk): 1·17, 95% CI: 0·99–1·38, P = 0·06) . Further research is warranted in this field.…”

“…Appropriate maternal thyroid function is of great concern throughout all trimesters. Overt hyperthyroidism and hypothyroidism during pregnancy have a well‐established detrimental impact on pregnant and obstetric consequences and offspring neurological development …”

“…Appropriate maternal thyroid function is of great concern throughout all trimesters. Overt hyperthyroidism and hypothyroidism during pregnancy have a well-established detrimental impact on pregnant and obstetric consequences 2,3 and offspring neurological development. 4 Subclinical hypothyroidism (SCH), defined as elevated TSH and normal free T4 (fT4) levels, with an incidence of 2-13Á7%, 5 is the most common thyroid disorder during pregnancy.…”

Brominated flame retardants in placental tissues: associations with infant sex and thyroid hormone endpoints

“…For example, THs are important in trophoblast proliferation and migration during placenta development, and restrictions on TH delivery to the placenta can lead to several disorders of the placenta [21]. In addition, maternal thyroid disorders have been associated with pre-eclampsia, placental abruption, and intra-uterine growth restriction (IUGR) [32–35]. Therefore, understanding environmental stressors that may affect thyroid regulation in the placenta is of critical importance.…”