Background and aims Congenital hypothyroidism, occurring approximately 1/2000 to 1/4000 newborns, is one of the most common preventable causes of mental retardation. The purpose of this study is to determine the incidence of this disease in Notre Dame De Secours University Hospital in Byblos-Lebanon and some characteristics factors of the disease (sex, preterm delivery, length and weight at birth, head circumference, maternal age, consanguinity).

Methods A total of 8364 newborns were screened by measuring newborn TSH, for a period of time between January 2009 and December 2015. The applied technique is based on measuring venous blood TSH levels which is different than using normal blood spots adopted for detecting congenital diseases. The sample included every newborn having a TSH level at birth>20 mU/L. All these newborns were followed and detailed medical record at birth were collected and analysed using SPSS program.

Results Out of 8364 screening test done, the number of newborn having TSH>20 is 669. When TSH repeated after 2–3 days, 636 patients presented a normal level while 33 children were diagnosed with congenital hypothyroidism (15 boys and 18 girls), giving an incidence of 33: 8364 (1: 253). This number is uncommonly high. As for the characteristics, we note a presence of a significant association between congenital hypothyroidism and the age of the mother (P value 0.03) and newborn weight (P value 0.04) and gestational age (p value 0.01). The other variables studied (sex, length at birth, head circumference, consanguinity of the parents), are not associated with congenital hypothyroidism. It is important to mention that 36 mothers out of 631 gave birth to 74 children having all TSH>20 at birth. Therefore it might be a possible relationship between having a child with TSH>20 and having another child from the same mother with TSH>20 (to be studied in further researches).

Conclusions The incidence of congenital hypothyroidism is about 1/253 in NDS University Hospital-Byblos. The risk of having a baby with Congenital Hypothyroidism increases with maternal age. Whereas the risk of the disease decreases when the weight of the newborn increases: odds ratios of 0.8 (0.6–0.9) and decreases when the gestational age is≥37 weeks, odds ratios of 0.3 (0.1–0.7)