An interesting link seems to exist between the presentation of Babies body during deliveries and the level of
maternal thyroid hormone. A process by which a baby in the breech position can sometimes be turned from buttocks or foot first to head first is known as 'External Cephalic Version' (ECV).
Recently, a group of scientists studied the maternal thyroid function and the outcomes of ECV outcome. They found that at 36 weeks of gestation, women whose TSH levels were above 2.5mIU/l were at risk for breech presentation. But fetal movements and mobility are prerequisites for spontaneous version in cephalic position.
As the gestational age increases the incidence of breech presentation decreases from approximately 16% at 32 weeks to 3-5% at term. To reduce the number of breech presentations and breech deliveries at term, ECV has been recommended by the American College of Obstetricians and Gynecologists (ACOG) and the Royal College of Obstetricians and Gynecologists (RCOG). Several factors like parity, type of breech, placenta location, amniotic fluid index (AFI) and engagement of the breech have been associated with successful ECV outcome.
Scientists studied about 141 women over a period of 2 years. Blood samples were collected before ECV. Women with breech presentation at 35 weeks were part of the study. The ECV success rate was 55%, with 85% in multipara and 39% in primipara. The TSH level was significantly higher in women with failed ECV's than those with successful ECV's
, while the levels of FT4 did not differ among the two groups. TSH, parity, type of breech and anterior location of placenta were all significantly related to successful outcome of ECV.
Normally maternal TSH and Fetal T4 are inversely related. Higher levels of maternal TSH reflect low circulating levels of fetal T4. Fetal neural maturation and fetal motility are affected due to low levels of fetal T4. Also breech babies have impaired neuromotor development, which hinders ECV outcome.
Poor fetal movements result in less expanded intra-uterine environment, which is required for successful ECV.
Thus scientists have concluded that higher TSH levels increase the risk of ECV failure