Thyroid disease in pregnancy—is routine assessment of fetal growth by ultrasound justified?

Abstract

In our experience significant fetal complications that could be directly attributable to thyroid disease are rare and therefore a retrospective study was carried out to determine whether routine serial ultrasound for fetal growth is justified in all women. Retrospective analysis of 43 women with thyroid disease in the period January 2000 to January 2002 was carried out. Thirty-five women had hypothyroidism and nine hyperthyroidism. Thirty-one women with hypothyroidism were on thyroxine. At booking, 40% were biochemically hypothyroid and 44% euthyroid. During the third trimester, 35% were biochemically hypothyroid and 49% euthyroid. Regular assessment of thyroid function every 6 weeks was not carried out among 26%. Serial growth scans were carried out in 32 women and 59% had three or more scans. Intrauterine growth retardation was diagnosed in 9% (n = 4), based on routine serial ultrasound scan. Five per cent had LBW, which was at 3rd centile when adjusted for gestation age. There was no significant increase in pregnancy complications. There was no significant increase in instrumental delivery or caesarean section.