Background
Methods/design
Aims
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Has the new policy of recommending iodine supplementation in preconception, throughout pregnancy and during lactation impacted the prevalence of iodine deficiency in pregnant women from the Minho region of Portugal when compared to the same population before the recommendation [6]?
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Does the time of initiation of iodine supplementation (if any) influence the serum levels of thyroid hormones at several intervals during pregnancy?
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Are there serum thyroid-hormone parameters in the 1st trimester of pregnancy that predict psychomotor development of the child at 18 months of age?
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What are the standard reference ranges for thyroid hormone parameters throughout pregnancy (not yet established for the Portuguese population)?
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Are there thyroid function parameters (e.g., the presence of anti-thyroid antibodies) that predict the response to iodine supplementation?
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Is the quality of breastmilk related to thyroid hormone parameters in a way that could suggest new intervention strategies for real-time milk fortification during lactation?
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Are the fetal heart rate and thyroid volume at age 3 months influenced by maternal iodine status?
Design
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M0-Baseline evaluation. Women before pregnancy (for planned pregnancies), at the beginning of pregnancy (for unplanned pregnancies) and women of childbearing age and not intending to become pregnant.
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M1-M2-M3-Women in each trimester of pregnancy.
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M3-Fetus.
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M4- Women and newborn. Delivery.
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M5-Women and progeny three months after delivery.
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M6-Women and progeny eighteen months after delivery
Moment | Evaluation | Filled in by: | Local | |
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M0 | Recruitment (preconception or 1st trimester) | Informed consent | Participant | Family health centers |
Sociodemographic evaluation | Participant | |||
Clinical evaluation | Clinician | |||
Food frequency questionnaire | Participant | |||
3 days food record | Participant | Home | ||
Blood and urine collection | Clinical Analysis Laboratory | |||
Thyroid ultrasound | Clinician | 2CA | ||
M1 | 1st trimester of pregnancy | Clinical evaluation | Clinician | Family health centers |
Blood and urine collection | Clinical Analysis Laboratory | |||
M2 | 2nd trimester of pregnancy | Clinical evaluation | Clinician | Family health centers |
Blood and urine collection | Clinical Analysis Laboratory | |||
M3 | 3rd trimester of pregnancy | Clinical evaluation | Clinician | Family health centers |
Blood and urine collection | Clinical Analysis Laboratory | |||
Thyroid ultrasound | Clinician | 2CA | ||
Fetal cardiotocography | Clinician/Nurse | Hospital Braga | ||
M4 | Birth | Clinical evaluation | Clinician | Hospital Braga |
Blood and urine collection - pregnant | Nurse | |||
Urine collection– Newborn | ||||
M5 | 3 months after birth | Breast milk collection | Nurse | 2CA |
Blood and urine collection – puerperal women | ||||
Urine collection – newborn | ||||
Thyroid ultrasound - puerperal women | Clinician | |||
Thyroid ultrasound - child | ||||
M6 | 18 months after birth | Child psychomotor evaluation | Researcher | 2CA |
Blood and urine collection –women | Nurse | |||
Urine collection – child |
Intervention
Setting and participants
Inclusion criteria
Exclusion criteria
Study parameters
Sample size calculation
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Regarding prevalence. For a statistical power of 99%, a type I error of 1%, a previous proportion of 88% iodine deficiency [4] and assuming a 70% decrease in the number of women with iodine deficiency, the required sample size is 122 participants (pregnant women). A comparison group of 122 women who do not plan to become pregnant will be enrolled from the same health care units to control for other environmental factors that may influence iodine intake and the prevalence of iodine deficiency.
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Regarding pregnancy thyroid hormone levels. For a statistical power of 99%, a type I error of 1%, a previous proportion of 17% women with the expected increase in total T4 in the 1st trimester of pregnancy [5], and assuming a 2-fold increase in this number, the required sample size is 304 participants.
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Regarding the prediction of psychomotor development. For a statistical power of 99%, a type I error of 1%, an Odds Ratio of 2 and Pr(Y = 1|X = 1) H0 = 0.25 (probability of the parameter to be studied being below percentile 0.25), the required sample size is 262 participants.