Effect of Contrast Agents on Pregnant Women
Many clinical conditions require radiological diagnostic exams based on the emission of different kinds of energy and the use of contrast agents. Pregnant patients who should be submitted for diagnostic examinations with contrast agents represent a group of patients with whom it is necessary to consider both maternal and fetal effects. Radiological examinations use different types of contrast media, the most used and studied are represented by iodinate contrast agents, gadolinium, Gastrograffin, barium sulfate. The present article reports the available data about each contrast agent and its effect related to the mother and fetus. This review aims to clarify the clinical practices to follow in cases where a radio diagnostic examination with a contrast medium is indicated to be performed on a pregnant patient.
Abbreviations
CT: Computed Tomography; PET: Positron emission tomography; MRI: Magnetic resonance imaging; FDA: food and drug administration.
Introduction
Many Clinical conditions require radiological diagnosis exams based on emission of different kind of energy and the use of contrast agent such as computed tomography (CT), PET, MR imaging, Ultrasound and x-ray imaging. In Radiological examinations we use different kind of contrast media such as iodinated contrast agents, gadolinium, gestrographin, barium sulfate and nano bubbles in contrast enhanced ultrasound. A non-iodinated contrast media is one that does not contain iodine and may instead contain barium or other non-iodinated media as the radio opaque substance. In recent times, there is an increased use of contrast agents in Pregnant women hence we should study the effect of contrast agents in maternal and fetal life. In the medical field, the use of contrast media in pregnant women is somehow restricted because we don’t have wide and prospective studies related to those patients and its effects on pregnant women or on its foetus. But we know the importance of contrast studies in such patients in particular case and we can minimize its effect of contrast media in such patients by using them properly and by following the international Association guidelines and by using ALARA (As low as reasonably achievable) principle.
Classification of Contrast Agents
Contrast agents can be defined as the agents introduced in a body during imaging Examinations to improve visualization of internal structures of the body. In medical imaging we use both ionic and non- ionic Contrast agents [1]. In computed Tomography iodinated agents are used to improve detection rate of imaging. The food and drug administration (FDA) classified the Iodinated contrast as pregnancy category B drugs as they are considered safe for pregnant women and lactating mothers. Animal reproduction studies have shown an adverse effect on animal foetus there are no well controlled studies in human beings and the effects of contrast agent on pregnant women and foetus. But there are potential benefits which may justify potential risks in human beings [2]. American college of obstetrics and gynecologists recommended the use of contrast agents for additional diagnosis [3].
Iodinate Contrast Agents
Iodinated contrast agents can be classified according to osmolarity, ionicity and number of benzene rings. The incidence of mild and moderate contrast reaction is higher for higher osmolar contrast media approximately 6-8% and it is lower for lower osmolar contrast media approximately 0-2% though their radiopacity is almost the same. Adverse effect on pregnant women is same as in general population like hypersensitivity, thyroid dysfunction, nephropathy. There is no evidence of tetrogenic or mutagenic effects on mother or foetus during pregnancy. The transplacental passage of ionic agents has been demonstrated on animals as the contrast agent enters into the foetus it removed in foetal urine. However there is no clear evidence of non-ionic contrast agents in transplacental passage. Cohort studies suggest that exposure to iodinated contrast agent during pregnancy may lead thyroid dysfunction in offsprings including transient hypothyroidism and goiter. The fetal thyroid is very active during 2nd trimester and a very sensitive to any iodinated agent and increases its uptake [4]. Major side effects are reported when ionic contrast media are administered during pregnancy and even in preconceptional phase in contrary non ionic iodine agents don’t affect TSH and T4 level in offspring [5, 6]. The European society of urogenital radiology recommended that neonatal thyroid function should be checked during 1st week of birth if iodinated contrast media was given during pregnancy [7]. Iopamidol is a non-ionic low osmolarity monomeric iodine agent which passes through placenta. It has been demonstrated to be a safe for foetal thyroid functions and reproductive outcome [8, 9]. Ultravist most used iodine based contrast agent in CT is non -ionic, low osmolarity hydrosouluble agent with transplacental passage. One case reported that it is increasing transient TSH level in the newborn when exposed during pregnancy without hormone dysregulation [6]. Use on pregnant women the safety of such media agent is widely evident nevertheless the Lack of clinical studies on humans favours the doubts about use on pregnant women (Table 1). As far as concerns related to breastfeeding, the iodinated contrast agents are clearly excreted from mother’s blood stream within 24hours and their half life is 2 hours less than 1% of contrast agent is excreted through milk [10].
| Guidelines | Iodinated Contrast Agents | Gadolinium-based Contrast Agents |
|---|---|---|
| Pregnancy | ||
| Considerations | Data on fetal exposure to iodinated contrast agents are scarce | Few studies have evaluated fetal exposure to gadolinium |
| No malformation or side effects have been reported in newborns | There have been no studies on long-term risks in humans | |
| Iodinated products given during pregnancy may induce neonatal hypothyroidism | Free gadolinium could potentially lead to neurotoxicity | |
| Recommendations | Screening newborns for hypothyroidism during the 1st week of life is standard pediatric practice | Consensus is that gadolinium should not be used during pregnancy unless the benefits outweigh the risks |
| Iodinated contrast agents must be essential for making the diagnosis | ||
| Informed consent as to the risks and benefits of the procedure is recommended | ||
| Use of topical iodine is contraindicated | ||
| Lactation | ||
| Considerations | Dose of iodinated contrast agent in breast milk absorbed by the infant is 0.5% of the maternal dose | About 0.01% of the maternal gadolinium dose is excreted into breast milk |
| Breast Feeding after the injection of iodinated contract agent is safe | Breast-feeding after the injection of gadolinium agent is safe |
- Concerned mothers may be instructed to discard breast mik for 24- hours after injection to eliminate fetal exposure to contrast agent
- Recommendations
- Use of topical iodine is contraindicated because free iodine excretion may induce neonatal hypothyroidism
Table 2: Guidelines of Contrast agents in Pregnancy.
Conclusion
In conclusion a mother can safely breastfeed their babies after exposure to an iodine contrast agent, however they can stop breastfeeding for 12-24hours if they are concerned. In cases where the use of radio diagnostic investigations with a contrast medium is necessary during pregnancy, it is therefore essential to discuss its use with patients, improve the advice given regarding the potential benefits that may occur, and provide them an adequate, informed consent. To date, large prospective studies are actually few in number, so further research should be strengthened to better investigate the risks and benefits of using contrast media in clinical practice and to enable their correct and informed use by physicians.
References
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Perelli F, Turrini I, Giorgi MG, Renda I, Vidiri A, et al. (2022) Contrast Agents during Pregnancy: Pros and Cons When Really Needed. Int J Environ Res Public Health 19(24): 16699.
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Leek JC, Arif H (2024) Pregnancy Medications. In: StatPearls. StatPearls Publishing; Treasure Island, FL, USA.
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Jain C (2019) ACOG Committee Opinion No. 723: Guidelines for Diagnostic Imaging during Pregnancy and Lactation. Obstet Gynecol 133(1): 186.
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Welie NV, Portela M, Dreyer K, Schoonmade LJ, Wely MV, et al. (2021) Iodine contrast prior to or during pregnancy and neonatal thyroid function: A systematic review. Eur J Endocrinol 184(1): 189-198.
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Satoh M, Aso K, Katagiri Y (2015) Thyroid Dysfunction in Neonates Born to Mothers Who Have Undergone Hysterosalpingography involving an Oil-Soluble Iodinated Contrast Medium. Horm Res Paediatr 84(6): 370-375.
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Tonacchera M, Chiovato L, Bartalena L, Cavaliere AF, Vitti P (2020) Treatment of Graves’ hyperthyroidism with thionamides: A position paper on indications and safety in pregnancy. J Endocrinol Investig 43(2): 257-265.
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Webb JAW, Thomsen HS, Morcos SK, ESUR (2005) The use of iodinated and gadolinium contrast media during pregnancy and lactation. Eur Radiol 15(6): 1234-1240.
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Fitzpatrick J, Speakman J, Kapfer SA, Holston AM (2011) Transplacental passage of the non-ionic contrast agent iopamidol in twins. Pediatr Radiol 41(4): 534-536.
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Atwell TD, Lteif AN, Brown DL, McCann M, Townsend JE, et al. (2008) Neonatal thyroid function after administration of IV iodinated contrast agent to 21 pregnant patients. AJR Am J Roentgenol 191(1): 268-271.
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American College of Radiology (2023) ACR Manual on Contrast Media. pp: 1-151.
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