Antithyroid drug therapy in pregnancy: a review of guideline recommendations

Prevention and control of non-communicable diseases in antenatal, intrapartum, and postnatal care: a systematic scoping review of clinical practice guidelines since 2011

BACKGROUND

Non-communicable diseases (NCDs) are a leading cause of maternal mortality and morbidity worldwide. The World Health Organization is developing new recommendations focusing on the management of NCDs for pregnant, intrapartum, and postnatal women. Thus, to support the development of new guidelines and recommendations, we aimed to determine the availability, focus, and scope of recommendations of current guidelines for the management of NCDs during pregnancy, intrapartum, and postnatal period.

METHODS

PubMed, Global Index Medicus, TRIP, and Guideline International Network databases were searched on 31 May 2021, to identify any NCD-related guidelines published between 2011 and 2021 with no language or country restrictions. Websites of 165 professional organizations were also searched. Characteristics of included guidelines were analyzed, and recommendations were extracted from guidelines of five high-priority NCD conditions (diabetes, chronic hypertension, respiratory conditions, hemoglobinopathies and sickle cell disease, and mental and substance use disorders).

RESULTS

From 6026 citations and 165 websites, 405 guidelines were included of which 132 (33%) were pregnancy-specific and 285 (88%) were developed in high-income countries. Among pregnancy-specific guidelines, the most common conditions for which recommendations were provided were gestational diabetes, circulatory diseases, thyroid disorders, and hypertensive disorders of pregnancy. For the five high-priority conditions, 47 guidelines were identified which provided 1834 recommendations, largely focused on antenatal care interventions (62%) such as early detection, screening tools, pharmacological treatment, and lifestyle education. Postnatal recommendations largely covered postnatal clinical assessments, lifestyle education, and breastfeeding. Health system recommendations largely covered multidisciplinary care teams and strengthening referral pathways.

CONCLUSIONS

This study provides a robust assessment of currently available guidelines and mapping of recommendations on NCD management within maternal health services, which will inform the scope of the World Health Organization's future guideline development activities. This study identified a need to develop guidelines that consider NCDs holistically, with an integrated approach to antenatal, intrapartum, and postnatal care, and that are relevant for resource-limited contexts. Any such guidelines should consider what interventions are most essential to improving outcomes for women with NCDs and their newborns, and how variations in quality of NCD-related care can be addressed.

Antithyroid drug therapy in pregnancy and risk of congenital anomalies: Systematic review and meta-analysis

OBJECTIVES

The risk of congenital anomalies following in utero exposure to thionamide antithyroid drugs (ATDs) is unresolved. Observational studies are contradictory and existing meta-analyses predate and preclude more recent studies. We undertook an updated meta-analysis of congenital anomaly risk in women exposed to carbimazole or methimazole (CMZ/MMI), propylthiouracil (PTU), or untreated hyperthyroidism in pregnancy.

METHODS

We searched Medline, Embase, and the Cochrane database for articles published up till August 2021. We pooled separate crude and adjusted risk estimates using random effects models and subgroup analyses to address heterogeneity.

RESULTS

We identified 16 cohort studies comprising 5957, 15,785, and 15,666 exposures to CMZ/MMI, PTU, and untreated hyperthyroidism, respectively. Compared to nondisease controls, adjusted risk ratio (RR) and 95% confidence intervals (95% CIs) for congenital anomalies was increased for CMZ/MMI (RR, 1.28; 95% CI, 1.06-1.54) and PTU (RR, 1.16; 95% CI, 1.08-1.25). Crude risk for CMZ/MMI was increased relative to PTU (RR, 1.20; 95% CI, 1.01-1.43). Increased risk was also seen with exposure to both CMZ/MMI and PTU, that is, women who switched ATDs in pregnancy (RR, 1.51; 95% CI, 1.14-1.99). However, the timing of ATD switch was highly variable and included prepregnancy switches in some studies. The excess number of anomalies per 1000 live births was 17.2 for patients exposed to CMZ/MMI, 9.8, for PTU exposure, and 31.4 for exposure to both CMZ/MMI and PTU. Risk in the untreated group did not differ from control or ATD groups. The untreated group was however highly heterogeneous in terms of thyroid status. Subgroup analysis showed more positive associations in studies with >500 exposures and up to 1-year follow-up.

CONCLUSIONS

ATD therapy carries a small risk of congenital anomalies which is higher for CMZ/MMI than for PTU and does not appear to be reduced by switching ATDs in pregnancy. Due to key limitations in the available data, further studies will be required to clarify the risks associated with untreated hyperthyroidism and with switching ATDs in pregnancy.

The Effect of Thyrotropin-Releasing Hormone and Antithyroid Drugs on Fetal Thyroid Function

A euthyroid pregnant woman will normally have a fetus that displays normal fetal development. However, studies have long demonstrated the role of T3 (Triiodothyronine), T4 (Thyroxine), and TSH (Thyroid Stimulating Hormone) and their degree of penetrability into the fetal circulation. Maternal thyrotropin-releasing hormone (TRH) crosses the placental site and, from mid-gestation onward, is able to promote fetal TSH secretion. Its origin is not only hypothalamic, as was believed until recently. The maternal pancreas, and other extraneural and extrahypothalamic organs, can produce TRH variants, which are transported through the placenta affecting, to a degree, fetal thyroid function. Antithyroid drugs (ATDs) also cross the placenta and, because of their therapeutic actions, can affect fetal thyroid development, leading in some cases to adverse outcomes. Furthermore, there are a number of TRH analogues that share the same properties as the endogenous hormone. Thus, in this narrative review, we highlight the interaction of all the above with fetal growth in uncomplicated pregnancies.

Maternal hyperthyroidism and pregnancy outcomes: A population-based cohort study

OBJECTIVE

Maternal hyperthyroidism and antithyroid medications have been associated with adverse pregnancy and perinatal outcomes. This nationwide register-based study investigated the association of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and included all singleton births in Finland between 2004 and 2013 (N = 571 785).

DESIGN, PATIENTS AND MEASUREMENTS

Hyperthyroid mothers were identified in the Medical Birth Register, and data on ATD use before and/or during pregnancy were collected from the Prescription Register. The odds ratios, with 95% confidence intervals, for adverse outcomes among hyperthyroid mothers and mothers without thyroid disease were compared using logistic regression.

RESULTS

In total, 2144 (0.37%) of all the women had diagnoses of hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Compared to the mothers without thyroid disease, maternal hyperthyroidism was associated with older age, multiparity, smoking, previous miscarriages, and overweight or obesity. The mothers diagnosed with hyperthyroidism also had increased odds of gestational hypertensive disorders, caesarean sections, placental abruptions, preterm births, small-for-gestational-age newborns and neonatal intensive care unit treatment. The odds of pregnancy and/or perinatal complications were higher among those who had used ATDs (indicative of active disease), but those who had not received ATD treatment also had increased odds of such complications compared to the mothers without thyroid disease.

CONCLUSIONS

Women with active hyperthyroidism and those with histories of hyperthyroidism should be considered at risk of developing pregnancy and perinatal complications and should therefore be monitored during pregnancy.

Study on the changes in TSH, TPO-Ab and other indicators due to Vitamin D deficiency in Pregnant Women with subclinical hypothyroidism in the first trimester

Objective:

To investigate the effect of vitamin D deficiency on the levels of thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPO-Ab), interleukin-1 (IL-1) and high-sensitivity C-reactive protein (hs-CRP) in pregnant women with early pregnancy complicated by subclinical hypothyroidism.

Methods:

A total of 172 pregnant women with subclinical hypothyroidism in the first trimester diagnosed and treated in a given hospital from August 2014 to May 2018 were selected, and their levels of vitamin D were determined. Depending on the abnormality of their vitamin D levels, the study participants were divided into two groups: the study group (vitamin D≤20 ng/L) and the control group (vitamin D>20 ng/L). The levels of TSH, TPO-Ab, IL-1 and hsCRP in the two groups were measured.

Results:

The levels of TSH, hsCRP and TPO-Ab in the study group were significantly higher than those in the control group (P<0.05). The comparison between the two groups in terms of IL-1 showed no statistically significant difference.

Conclusion:

Vitamin D deficiency in the first trimester is associated with in an increased level of TSH in the first trimester, thereby aggravating subclinical hypothyroidism. The mechanism may be associated with the impact of vitamin D deficiency on hs-CRP and other body inflammation indicators, as well as on thyroid autoantibodies and other immune indicators, but has no effect on IL-1 levels.

Safety of antithyroid drugs in pregnancy: update and therapy implications

Introduction: The thionamide antithyroid drugs, methimazole (MMI), its pro-drug derivative carbimazole (CMZ), and propylthiouracil (PTU) are the mainstay of treatment for hyperthyroidism in pregnancy. However, antithyroid drugs carry risks of adverse effects that can affect fetal and maternal well-being.Areas covered: This review provides an update on the safety of antithyroid drugs in pregnancy, focusing on the most serious concerns of severe liver disease and congenital anomalies.Expert opinion: PTU-induced liver disease is uncommon but can run a catastrophic course in pregnancy with a risk of liver failure and threats to maternal or fetal survival. Acute pancreatitis is a relatively rare occurrence that has been linked to thionamide use in a handful of reports in non-pregnant individuals. Observational studies on the risk of birth defects with antithyroid drug exposure in pregnancy overall show an increase in birth defect risk with exposure to CMZ/MMI, and to a lesser extent, PTU. Further studies are required to determine whether the currently recommended approach of switching between thionamide drugs in pregnancy improves outcomes. Ultimately, a preventative strategy of offering definitive therapy to hyperthyroid women of childbearing potential offers the best approach to truly reduce the risks of antithyroid drug adverse effects in pregnancy.