Design
Cluster randomised, controlled, multicentre trial. Randomisation unit: primary care team (PCT).
Setting
46 PCTs from the province of Barcelona that provide health coverage to urban, semirural and rural populations.
Study population
All the pregnant women over the age of 17 years attending consultation to a midwife during the first trimester of gestation in the different participating PCC during the study period (2007-2010).
Exclusion criteria
Pregnant women in the second or third trimester of gestation; pregnant women with diagnosed thyroid disease; pregnant women without a telephone; pregnant women with communication difficulties (cognitive or sensory deterioration, language barrier); pregnant women who do not consent to participate in the study.
Sample size calculation
The sample size has been calcuated by multipying the size of a randomized simple design by the design effect. For the simple randomized design an alpha error of 0.05 and a beta error of 0.20 in a bilateral contrast are considered, requiring 204 pregnant women in the intervention group and 204 in the non intervention group to detect a difference greater than or equal to 15% in the prevalence of iodine deficiency between the two. After extensive review of the literature on group educational interventions in a pregnant population, the investigative team [37–40] considered that the intervention to be undertaken in the intervention group will achieve an improvement of at least 15% in hygienic-dietetic habits and thus in the levels of ioduria. A proportion of iodine deficiency of 44% in the non intervention group is assumed as indicated by studies performed in populations in the Pyrenees and the coast of the Maresme, areas near the study setting [18]. A loss to follow up of 15% has been estimated. Using an intracluster correlation coefficient of 0.05 [41–43], and based on an average of 25 pregnant women per PCT, the design effect is 2.2. Therefore, 898 pregnant women and 36 PCT are needed.
Data Collection
Dependent Variables: iodine deficiency (yes, no), is defined as ioduria less than 150 μg/lL
Independent Variables:
Variables related to the woman (information obtained through a individualized interview):
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Administrative: PCT, midwife, data collection date, patient code, telephone number.
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Sociodemographic: date of birth, level of education, etnia.
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Obstetric: n° of pregnancies brought to term; n° premature births, n° of miscarriges and n° of live births, trimester of gestation of the woman (1st, 2nd or 3rd).
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Related to smoking: smoker (no, yes), cigarettes/day prior to gestation, cigarettes/day during gestation, ex-smoker because of pregnancy, ex-smoker and time since cessation of smoking.
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Related to consumption of iodine-rich foods:
▪ Consumption of milk: glasses/day
▪ Consumption of yoghourt: units/week and type (whole or skimmed).
▪ Consumption of cheese: rations/week and type (cured, semi-cured and fresh).
▪ Consumption of vegetables: times/week, usual preparation (raw, fried, grilled/baked, steamed, boiled) and use of water in which they have been boiled (yes, no and no answer).
▪ Consumption of vegetables and garden produce: times/week.
▪ Consumption of fish: times/week, usual preparation (raw, fried, grilled/baked, steamed, boiled).
▪ Consumption of tinned tuna: times/week.
▪ Consumption of tinned sardines: times/week.
▪ Consumption of meat and derivatives: times/week.
▪ Consumption of eggs: units/week.
▪ Consumption of fruit: units/week and types (strawberries, pineapple, peaches, bananas, oranges and others).
▪ Consumption of nuts: times/week.
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Consumption of iodised salt: yes (time of consumption), no.
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Consumption of multiple vitamins containing iodine: yes (type), no.
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Consumption of potassium iodine supplement: yes (type), no.
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Related to the intervention: study group (intervention, non intervention), attendance to group workshop (yes, no).
Variables related to the midwife (information obtained through a individualised interview): years in the profession, primary care nursing training, mean number of visits per day.
Variables related to the PCT (information obtained through an individualised interview): population assigned, mean age of population assigned, whether or not it is a teaching center for residents, number of midwives.
Description of the Study
The phases of the study are:
* PHASE 1. Recruitment of primary care nurses (PCN): the project was presented to all the PCN within the study setting to recruit midwives interested in participating. Those who were interested in collaborating signed a document of commitment to participate in the study.
* PHASE 2. Creation of the study groups (intervention-IG and non intervention-NIG) and midwife training programme:
- The randomisation unit was the PCN. Using simple randomisation the centres distributed the IG and NIG at a proportion of 1:1.
- The formation of the participating midwives was carried out on 3 centralised work days during which the develpment of the study was explained in depth and they were given instructions on correct completion of the questionnaire on hygienic-dietetic habits in both a paper and electronic format. Each professional was assigned a support investigator to clarify any doubts which may arise during the study period. The objective of session was for the midwives to obtain sufficient training to avoid possible variability in the development of the study and in the collection and registration of data.
* PHASE 3. Pilot study: this was carried out in three randomly selected PCN with 30 pregnant women who were not included in the study in order not to affect the final results. This pilot study evaluated the study inclusion process of the pregnant women, data collection by paper and electronic questionnaire as well as the appointment circuit, referral and presentation of ioduria results.
* PHASE 4. Recruitment of the pregnant women, initial evaluation and request for first ioduria (in IG and NIG)
- Recruitment of the pregnant women: the pregnant women will be consecutively recruited from the women attending consultation to the midwife until the number of 25 women required by each PCN has been reached. Each midwife will know the number of women that they must recruit for the study. If a pregnant woman fulfils the inclusion criteria the midwife will explain the study to her and will ask for her participation. If the woman accepts she will be given the study information sheet in which the objectives and the characteristics are described and she will be asked to sign the informed consent form to thereby be included in the study. If the woman refuses to participate the reasons for this will be noted, as will the administrative, sociodemographic and obstetric variables with the aim of determining the profile of this type of pregnant woman.
- Initial evaluation of the pregnant women: on the first contact with the women and through an individualised interview the midwife will collect the following variables: administrative, sociodemographic, obstetric, those related to smoking, consumption of foods rich in iodine, iodised salt and iodised multiple vitamins. All the data will be reported in an electronic data collection file (EDCF) which will include the rule of internal coherence to guarantee the quality control of the data. Following the interview the midwife will make an educational intervention on the importance of good alimentation during pregnancy and the repercussions this has on maternal and foetal health, with special emphasis on the importance of the consumption of foods rich in iodine and iodised supplements. An informative sheet will also be provided on the importance of iodine during gestation.
- Request for ioduria during the first trimester: the midwife will request an ioduria test and will explain the woman how to correctly collect the urine and will program the appointment for the second trimester visit of the pregnancy. On receipt of the ioduria results the midwife will note these in the EDCF. In cases in which iodine deficiency is detected the midwife will duly intervene, thus the reason for including the telephone number of the pregnant woman in the questionnaire. If iodine supplementation is indicated the administration will begin on collection of the first urine sample to avoid underestimation of the prevalence of iodine deficiency in the first trimester. Ioduria will be analysed using the Benotti&Benotti method performed in the laboratory of the Hospital Clinic of Barcelona.
* PHASE 5. Group Education Intervention (only in IG): the coordinating midwives in each zone will be responsible for performing the educational workshops on hygienic-dietetic habits in the pregnant women in the intervention group. This workshop will be held in the first trimester since this is when organogenesis is produced and is therefore the time of greatest risk for the appearance of alterations in the development of the foetal central nervous system in cases of maternal iodine deficiency. The content of the educational workshop will be the same to avoid a variation in information and transmission of knowledge to the pregnant women, that is, to ensure receipt of homogeneous information by the pregnant women.
* PHASE 6. Follow up (in IG and NIG): if a pregnant woman does not attend the appointment she will be called by telephone and if she cannot be contacted after 10 attempts she will be withdrawn from the study. The interview on hygienic-dietetic habits will be given in the second and third trimester appointments and determination fo ioduria will be requested. The reasons for participant withdrawal will be reported and a flow chart of the patients will be created throughout the study.
* PHASE 7. Validation of the questionnaire on the iodine nutritional status in pregnant women: the questionnaire has been elaborated by the investigator team after extensive review of the literature and finally based on the alimentary table according to iodine content (mcg/100 g) included in the monography on "Los alimentos y la salud" (Food and Health) (Egura R. Webb S. Tovar JL. Y Gausí C. Los minerales y la salud. Barcelona: Nuevas Ediciones de Bolsillo, S.L.; 2000. p 161-97). The questionnaire describes the foods with the greatest iodine content and the quantities consumed, the use of iodised salt and multiple vitamins containing iodine and smoking since the latter is a goitrogenic substance. Neither the origin of the foods nor the place in which the food is prepared is taken into account because of the impossibility to evaluate and confirm these aspects, despite the influence in the quantity of iodine consumed. Validation will be undertaken by an expert in psychometry from the Autonomous University of Barcelona (UAB) taking into account ioduria values.
* PHASE 8. Completion of data collection: after performing the third trimester appointment data collection will be concluded. The periodic controls of the data reported in the EDCF will have localised and corrected any incoherences that may have arisen.
* PHASE 9. Data analysis and diffusion of the results: the data obtained will be analysed and a final report will be elaborated with diffusion of the results in different scientific scenarios.
Statistical analysis
Data will be analysed in concordance with the Consort Cluster guide [44], and all analyses will be done on an intention to treat basis. A descriptive analysis and an analysis of baseline comparability between the study groups will be performed for the variables studied. A Student's t test or a Mann-Whitney U test will be used to compare means with two categories. An ANOVA test will be done to compare means with two or more categories, and a Chi- squared test or a Chi -squared tendency test will be done to compare categorical variables. A multilevel logistic regression will be carried out to evaluate the association between the dependent and the independent variables that were statistically significant in the bivariate analysis. All analyses will be adjusted for potential confounding factors and for variables with clinical relevance. All tests will be done with a 95% bilateral confidence interval. SPSS 15, STATA 10 and HLM6 will be used.
Quality Control
Several procedures are employed to ensure the quality of the study data, thus maximizing the validity and reliability of the program delivery and outcome assessments. These are:
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Formation of the professionals participating in the study.
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Use of an electronic data collection system with a system of warnings and internal coherency norms.
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Regular meetings and mailings between members of the study group and all participating centres.
Ethical Aspects
In the first contact with the pregnant woman, she will be given information about the study and will sign an informed consent form if she wishes to participate. The informed consent will describe the ethical conditions and the participant's right to intimacy, anonymity, confidentiality, withdrawal and information. The investigators are committed to respecting the norms of good clinical practice, as well as the requirements of the Helsinki Declaration. The protocol has been evaluated and approved by the Ethical Committee of Scientific Research of the Primary Care Research Institute Jordi Gol (Barcelona, Spain). Confidentiality of data: Only the investigators and monitors/auditors of the study will have access to the data of the subjects who agreed to participate.