Irradiation and radiocontamination during pregnancy

Effects of fetal involvement of inadvertent radioactive iodine therapy for the treatment of thyroid diseases during an unsuspected pregnancy

Radioactive iodine (¹³¹I) therapy is absolutely contraindicated in pregnancy, but reports of inadvertent exposure continue to appear in the literature. Radiation-induced effects on the embryo/fetus are highly dependent on the stage of pregnancy, the dose absorbed by the embryo/fetus, and the manifestations of the pathological condition that develops as a result of the irradiation. Prior to implantation, the major concern is death of the embryo when exposed to radiation greater than the 100 mGy threshold. At this very early stage of pregnancy, exposure to ¹³¹I is unlikely to cause major malformations or thyroid dysfunction in surviving embryos. Exposure during organogenesis of the thyroid (from 10 weeks of gestation onward) and that of other organs at radiation thresholds of 100-300 mGy may result in fetal thyroid ablation, malformations, growth restriction, and in later life, mental retardation (MR). In addition, any dose of radiation exposure may increase the risk of cancer many years after the in utero exposure. Fetal and neonatal hypothyroidism due to in utero ¹³¹I exposure may require lifelong thyroxine replacement therapy and result in severe MR if the condition is not recognized immediately. Therefore, thyroid function must be evaluated and replacement therapy should be started without delay even before birth. Physicians treating women of childbearing age with ¹³¹I need to be aware of the risks of in utero ¹³¹I exposure and take all measures to avoid inadvertent exposure during pregnancy. Nevertheless, in case of accidental exposure, the clinician should confirm the gestational age at exposure, evaluate the risks to the fetus by estimating the radiation dose delivered, and discuss the subsequent management plan with the pregnant woman. This review aimed to summarize the current knowledge regarding the risk of harm to the developing fetus after in utero ¹³¹I exposure, especially focusing on the effects on thyroid function. This study also evaluated the most significant new findings regarding the prevention and in utero and peripartum management of fetal exposure to ¹³¹I.

The effects of ionizing radiation, microwaves, and ultrasound on the developing embryo: clinical interpretations and applications of the data

The term "radiation" evokes emotional responses both from lay individuals and from professionals. Many spokespersons are unfamiliar with radiation biology or the quantitative nature of the risks. Frequently, microwave, ultrasound, and ionizing radiation risks are confused. Although it is impossible to prove no risk for any environmental hazard, it appears that exposure to microwave radiation below the maximal permissible levels present no measurable risk to the embryo. Ultrasound exposure from diagnostic ultrasonographic imaging equipment also is quite innocuous. It is true that continued surveillance and research into potential risks of these low-level exposures should continue, but at present ultrasound not only improves obstetric care but also reduces the necessity of diagnostic x-ray procedure. In the field of ionizing radiation, we have as good a comprehension of the biologic effects and the quantitative maximum risks as of any other environmental hazard. Although the animal and human data support the conclusion that no increases in the incidence of gross congenital malformations, intrauterine growth retardation, or abortion will occur with exposures below 5 rad, that does not mean that there are definitely no risks to the embryo exposed to lower doses of radiation. Whether there exists a linear or exponential dose-response relationship or a threshold exposure for genetic, carcinogenic, cell-depleting, and life-shortening effects has not been determined. In establishing maximum permissible levels for the embryo at low exposures, we use the information in Tables 2, 3, 4, 7, 10, and 14. It is obvious that the risks of 1-rad or 5-rad acute exposure are far below the spontaneous risks of the developing embryo, since 15% of human embryos abort, 2.7%-3.0% of human embryos have major malformations, 4% have intrauterine growth retardation, and 8%-10% have early- or late-onset genetic disease. The maximum risk attributed to a 1-rad exposure, approximately 0.003%, is thousands of times smaller than the spontaneous risks of malformations, abortion, or genetic disease (see Table 10). Thus, the present maximum permissible occupational exposures of 0.5 rem for pregnant women and 5 rem for medical exposure are extremely conservative. Medically indicated diagnostic roentgenograms are appropriate for pregnant women, and there is no medical justification for terminating a pregnancy in women exposed to 5 rad or less because of a radiation exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Hysterosalpingography

A brief review of the technique of hysterosalpingography is provided. It remains an important diagnostic study in searching for causes of infertility. HSG is a safe, simple procedure that enables the lumina of the uterine cavity and fallopian tubes to be outlined. Fundamentals in techniques have been stressed so as to limit the errors of omission and commission. During the course of many years, I have been honored by my colleagues, who have requested me to review interesting HSGs. Thus, I have been able to accumulate a series of x-rays that I can share with the readers of Modern Trends. Although these photographs seemed unique, many of them probably have been seen by other investigators. They are presented because of their important diagnostic features.

Brain tumors and pregnancy. Presentation of a case and a review of the literature

A case of brain tumor complicating a full-term pregnancy is reported. The literature is reviewed to show the effect of pregnancy on these tumors, the method of diagnosis, and management. Pregnancy often unmasks the existence of an intracranial neoplasm. The diagnosis can easily be missed, as the symptoms such as headache, vomiting, visual disturbance etc. are often encountered in pregnancy with or without pre-eclampsia. A high index of suspicion on the part of the obstetrician is a key to timely diagnosis. Computerized axial tomography is extremely useful in confirming or refuting the diagnosis of brain tumor. Generally speaking, neurosurgical intervention is best deferred until after delivery. In most cases, pregnancy may be allowed to continue under close supervision until the baby is reasonably mature. Labor may be induced in suitable cases, and the baby should be delivered by elective forceps as soon as the second stage of labor is reached to cut down maternal bearing-down efforts.

Environmental pollution and pregnancy: risks and uncertainties for the fetus and infant

Numerous environmental contaminants can affect the developing embryo, fetus, or infant. This essay explores such questions as these: What is the importance in mutagenesis and teratogenesis of macroenvironmental pollutants such as the heavy metals, dioxin derivatives, polychlorinated diphenyl compounds, and pesticides? What is the significance of microenvironmental pollutants (or social environmental factors) such as tobacco smoke, alcohol, and pharmacologic agents over which exposed individuals have considerable control? What are some of the ethical and legal implications of these toxins of which clinicians should be aware?

Influence of ionizing radiation on fetoplacental growth in mice

The effects of single doses of 60Co whole-body irradiation were studied in about 600 inbred primiparous Swiss-Webster mice on gestational day 9, 10, 11, or 12. The embryos and their placentas were weighted from day 13 to 18. A reference model surveyed the response of the conceptus to varying doses. A significant reduction in the fetal wet weight was observed as follows: day 9, 150-175 r.; day 10, 125-150 r.; day 11, 75-175 r.; day 12, 125-450 r. Beyond the upper-limit doses, a high mortality rate was detected, i.e., 64.5 per cent on day 10 at 175 r. and 63 per cent on day 11 at 200 r. The rapid growth period of the placenta extended from day 13 to 15. By this latter stage it had practically reached its maximum development. The placental index decreased progressively from day 13 to 18; however, this index was higher than the control on day 12 in treated animals, while lower on day 9, 10, or 11.