Association of Thyroid Function Test Abnormalities and Thyroid Autoimmunity With Preterm Birth: A Systematic Review and Meta-analysis

Importance

Maternal hypothyroidism and hyperthyroidism are risk factors for preterm birth. Milder thyroid function test abnormalities and thyroid autoimmunity are more prevalent, but it remains controversial if these are associated with preterm birth.

Objective

To study if maternal thyroid function test abnormalities and thyroid autoimmunity are risk factors for preterm birth.

Data Sources and Study Selection

Studies were identified through a search of the Ovid MEDLINE, EMBASE, Web of Science, the Cochrane Central Register of Controlled Trials, and Google Scholar databases from inception to March 18, 2018, and by publishing open invitations in relevant journals. Data sets from published and unpublished prospective cohort studies with data on thyroid function tests (thyrotropin [often referred to as thyroid-stimulating hormone or TSH] and free thyroxine [FT4] concentrations) or thyroid peroxidase (TPO) antibody measurements and gestational age at birth were screened for eligibility by 2 independent reviewers. Studies in which participants received treatment based on abnormal thyroid function tests were excluded.

Data Extraction and Synthesis

The primary authors provided individual participant data that were analyzed using mixed-effects models.

Main Outcomes and Measures

The primary outcome was preterm birth (<37 weeks' gestational age).

Results

From 2526 published reports, 35 cohorts were invited to participate. After the addition of 5 unpublished data sets, a total of 19 cohorts were included. The study population included 47 045 pregnant women (mean age, 29 years; median gestational age at blood sampling, 12.9 weeks), of whom 1234 (3.1%) had subclinical hypothyroidism (increased thyrotropin concentration with normal FT4 concentration), 904 (2.2%) had isolated hypothyroxinemia (decreased FT4 concentration with normal thyrotropin concentration), and 3043 (7.5%) were TPO antibody positive; 2357 (5.0%) had a preterm birth. The risk of preterm birth was higher for women with subclinical hypothyroidism than euthyroid women (6.1% vs 5.0%, respectively; absolute risk difference, 1.4% [95% CI, 0%-3.2%]; odds ratio [OR], 1.29 [95% CI, 1.01-1.64]). Among women with isolated hypothyroxinemia, the risk of preterm birth was 7.1% vs 5.0% in euthyroid women (absolute risk difference, 2.3% [95% CI, 0.6%-4.5%]; OR, 1.46 [95% CI, 1.12-1.90]). In continuous analyses, each 1-SD higher maternal thyrotropin concentration was associated with a higher risk of preterm birth (absolute risk difference, 0.2% [95% CI, 0%-0.4%] per 1 SD; OR, 1.04 [95% CI, 1.00-1.09] per 1 SD). Thyroid peroxidase antibody-positive women had a higher risk of preterm birth vs TPO antibody-negative women (6.6% vs 4.9%, respectively; absolute risk difference, 1.6% [95% CI, 0.7%-2.8%]; OR, 1.33 [95% CI, 1.15-1.56]).

Conclusions and Relevance

Among pregnant women without overt thyroid disease, subclinical hypothyroidism, isolated hypothyroxinemia, and TPO antibody positivity were significantly associated with higher risk of preterm birth. These results provide insights toward optimizing clinical decision-making strategies that should consider the potential harms and benefits of screening programs and levothyroxine treatment during pregnancy.

Mediterranean dietary pattern in pregnant women and offspring risk of overweight and abdominal obesity in early childhood: the INMA birth cohort study

BACKGROUND

Animal models have suggested that maternal diet quality may reduce offspring obesity risk regardless of maternal body weight; however, evidence from human studies is scarce.

OBJECTIVE

The aim of this study was to evaluate associations between adherence to the Mediterranean diet (MD) during pregnancy and childhood overweight and abdominal obesity risk at 4 years of age.

METHODS

We analysed 1827 mother-child pairs from the Spanish 'Infancia y Medio Ambiente' cohort study, recruited between 2003 and 2008. Diet was assessed during pregnancy using a food frequency questionnaire and MD adherence by the relative Mediterranean diet score (rMED). Overweight (including obesity) was defined as an age-specific and sex-specific body mass index ≥85th percentile (World Health Organization referent), and abdominal obesity as a waist circumference (WC) >90th percentile. Multivariate adjusted linear and logistic regression models were used to evaluate associations between pregnancy rMED and offspring overweight and abdominal obesity.

RESULT

There was no association between rMED and body mass index z-score, whereas there was a significant association between higher adherence to MD and lower WC (β of high vs. low rMED: -0.62 cm; 95% confidence interval: -1.10, -0.14 cm, P for trend = 0.009).

CONCLUSION

Pregnancy adherence to the MD was not associated with childhood overweight risk, but it was associated with lower WC, a marker of abdominal obesity.

Towards guidelines for dialysis in children with end-stage renal disease

There are few data describing the current practices of treatment selection for children with end-stage renal disease (ESRD). In an effort to establish a consensus among Spanish pediatric nephrologists for inclusion and exclusion criteria for renal replacement therapy in children with ESRD, in 1995 we surveyed members of the Spanish Pediatric Nephrology Association. Although only 43% of members responded, pediatric nephrologists and bioethicists studied the results and compiled a list of ten guidelines for treatment of children with ESRD. The proposed guidelines are meant to be a starting point for further discussion. An emphasis on flexibility, individual case assessment, and consideration of the best interests of the patient must remain central to any treatment plan. Decision making should ideally be shared by parents, professionals, the child, when appropriate, and ethics committees, as necessary.

[The efficacy of iodine prophylaxis in the prevention of endemic goiter in the southwestern area of Asturias]

The aim of the present work was to assess the prevalence of the endemic goiter in Asturias southwestern area (46,000 inhabitants; 6,638 in school age), after 10 years of iodized salt introduction in diet. 317 schooling children were randomly chosen (stratified by age, sex and geographic area). We evaluated thyroid gland size and urinary iodine excretion (microgram of iodine per gram of creatinine = I/C). Previously, studies of infantile population suggested a 63% of prevalence. Our results indicate a decrease to 16.4% of endemic goiter prevalence. Nevertheless, the success of iodine prophylaxis was heterogeneous and not good in some case: point out Ibias population with a prevalence of 48.5% (2,000 inhabitants and 353 in schooling). Remainder population was prevalences between 6.9% and 19.8%. The mean of urinary iodine excretion increased to I/C = 106 (previously I/C = 53). The smallest index I/C become to Ibias population = 78. (p < 0.01 and p < 0.05 with regard to Cangas del Narcea and Tineo population respectively). Only 2 of the 52 cases of goiter were hypothyroidism (but because of autoimmune thyroiditis). We conclude that iodine prophylaxis with salt was effective generally, in order to diminish the endemic goiter in the area.