Previously, studies have shown that children of women with thyroid autoantibodies experience more birth complications and poorer health in their first days. Studies have also shown later signs of cognitive developmental challenges (risk of attention deficit/hyperactivity problems) among children of mothers with autoimmune thyroid disease and/or subclinical hypothyroidism. In Denmark there is no formalized screening or treatment of subclinical thyroid disease - with or without Thyroid Peroxidase Antibodies (TPO-antibodies) - among pregnant women.

The hypothesis of this study is that the offspring of women with subclinical thyroid disease have a mitochondria-dysfunction which leads to more complications during birth, poorer health and well-being in the early childhood. The investigators will test this by recruiting mothers by a blood sample in the third trimester of pregnancy, screen the cord blood at birth and later on test the children with Bayley test two times in the early childhood.

Prior to a planned caesarean section, maternal blood samples are drawn and at the cesarean, cord blood samples are drawn, when the cord is clamped and cut. Thyrotropin, free T3, free T4, anti-TPO and lipids are measured on maternal as well as cord samples. Flow cytometry is performed to measure mitochondrial function. At age 6 months and 15 months the child´s development is evaluated by the Bayley-III test.

Inclusion Criteria:

• Singleton pregnancy, clinically healthy

Exclusion Criteria:

• Twin-pregnancy, metabolic disorder, medication or other diseases with a potential adverse impact on the pregnancy and fetus

The study population will be selected among pregnant women in region Zealand that will give birth by cesarean section