Fertility in adult females with congenital hypothyroidism (CH) diagnosed by neonatal screening

Background: CH interferes with human reproductive physiology, reduces the likelihood of pregnancy and adversely affects pregnancy and perinatal outcome. However, in subjects with early treated CH, a normal pubertal development has been reported. There are no systematic studies about fertility and pregnancy outcome in affected adults. Objective and hypotheses: Fertility and pregnancy evalutation in CH adult females. Methods: Gynecologic history was evaluated in a semistructurated questionnaire carried out by expert clinicians. The results were compared with data derived from national register of births. 155 girls with permanent CH between 1978 and 1994, in 4 italian regions, were recalled. 69 (44.6%) subjects (mean age 22.1 ± 4.4 yrs; 25 (36%) athyreosis, 32 ectopic gland (47%), 12 (17%) in situ gland) agreed to participate our study. Results: 9 pts reported 10 pregnancies (15%),3 of which terminated by abortion (1 miscarriage: 6° week of GA in 28.4 yrs pt with ectopic thyroid gland; 2 elective abortion: 4° week of GA in 20.2 yrs pt with hypoplasia, 6° week of GA in 21.3 yrs pt with athyreosis). The abortion rate was 1.45% for miscarriage (0.54% in control population), 2.9% for elective abortion (0.86% in control population).In the fullterm pregnancies the mean increase of L-T4 dose needed in each trimester was 15% (10%-20%), 15%(10%-20%) and 20%(10%-30%) respectively. TSH values >2.5 mU/L were found in 7/7 cases in the 1st trimester, in 4/7 in the 2nd, in 4/7 in the 3th. All newborn showed normal results at neonatal screening and at thyroid ultrasound. The table shows the data of live births subdivided according to maternal age. Conclusions: These preliminary data seem to indicate a normal fertility in patients with CH. The abortion rate seems to be higher than in control population. The monitoring of L-T4 dose adequacy in pregnancy is poor in our patients. These data warrant further investigation to evaluate the impact of genetic or therapeutic factors.