Influence Of Thyroid Disorders On Pregnancy And Its Outcomes

Background and objective: Thyroid disorders are common disease in reproductive women. It is noticed that maternal thyroid dysfunction during pregnancy, especially hypothyroidism, hyperthyroidism and thyroid autoimmunity disorders can lead to both obstetrical complications and adverse reproductive outcomes. Not only overt, but also subclinical thyroid disorders are high risk for pregnancy. Hypothyroidism is a chronic but progressive disease, without overt clinical characteristics, so thyroid function screening in high-risk women is necessary, and treatment should be caught out in time. Subclinical hypothyroidism is moving with a result of overt hypothyroidism, which is related to the increased level of TSH, as well as the positive thyroid peroxidase antibody (TPOAb). Hyperthyroidism can lead to severe complications on both mother and offspring, which is only next to gestational diabetes. However the adverse effect is minor if mothers get treatment during pregnancy. The aim of this study was to monitor the change of thyroid function and antibody during the course of pregnancy in those who suffer from various thyroiddisorders and normal control. We evaluate the consequences of pregnancy outcomes and determine management and therapeutic intervention in relation to pregnancy outcomes, providing to clinical obstetrician as a theoretically proof.METHOD: A descriptive analysis involving 303 pregnant women who visited and delivered in Shanghai first people's hospital from March 2006 to March 2007. Firstly, those having a medical history of thyroid dysfunction were allotted to a high-risk group and the remaining ones to the other group. Then, with high-sensitive immunofluorometric assay (IFMA) or radioimmuno assay(RIA) technique, we analyzed the concentrations of thyroid stimulating hormone (TSH), free triiodo-thyronine (FT3), free thyroxine (FT4) and TPOAb in pregnant women during their first antenatal visit. According to the results of thyroid function tests assessed by standard laboratory reference ranges, we classified them into different groups. The diagnostic criteria for overt hypothyroidism was TSH>4.0 mU/L accompanied by decreased FT4 and/orFT3 levels, and for subclinical hypothyroidism was TSH>4.0 mU/L with normal FT4 and FT3 levels. Overt hyperthyroidism was diagnosed when both TSH<0.25 mU/L and FI'4 and/orFT3 levels were elevated. The measured data of thyroid function , the ratio of positive TPOAb(>15U/mL) and the incidence of obstetrical complications andadverse outcomes were analyzed.Results: ① Thyroid function in controlled hypothyroidism group is in the reference range, and no significant difference is showed compared to the normal group (P>0.05). The level of TSH in the uncontrolled hypothyroidism increase in second trimester, with decreased FT3 and FT4, this change is obvious in last trimester. But the TSH level during second and last trimester was higher in subclinical hypothyroidism group than compared group (P<0.01).(2) The ratio of positive TPOAb in a high-risk group were significantly higher than those without a past history of thyroid disease (P<0.01). Significant higher ratio of elevated concentrations of TPOAb titers were found in the hypothyroidism group, both treated and uncontrolled (P<0.01) (3) We observed that significantly higher incidences of adverse obstetrical outcomes and complications in uncontrolled hypothyroidism group, compared with normal group and subclinical hypothyroidism group (P<0.01). No adverse outcome was found in controlled hyperthyroidism group, and also no conspicuous increased incidence of the complications compared with normal group (P>0.05). The incidences of adverse outcomes is obviously increased in women who have a high risk than those without a past history of thyroid disease (P<0.01).④ According to the TSH level, we divide the study women into four groups, as TSH≥10mU/L, TSH 4-10mU/L, TSH 2-4mU/L and TSH≤ 2mU/Lgroup. Following the raising of TSH level, the incidences of adverse outcomes and complications were increased. (5) In the controlled hyperthyroidism group, thyroid function was in the reference range during the entire gestation period. The level of TSH in the second trimester, was a little lower than in normal group (P<0.01). None of these 10 patients were TSH receptor antibody (TRAb) positive. However there was no significant difference in last trimester (P>0.05). We observed no adverse obstetrical outcomes in controlled hyperthyroid-dism group, and also no conspicuous increased incidence of the complications compared with normal group (P>0.05).Conclusion: Presence of clinical thyroid disorders, past history of thyroid disease or thyroid autoimmune disorders can negatively affect the pregnancy. However, if mothers with thyroid disease get adequate treatment in time and remain thyroid function normal, the adverse influence may be reduced to the least. So serial monitoring and therapeutic intervention may be necessary for the prevention of undesirable obstetric outcomes.