Adverse effects of prenatal methimazole exposure.
BACKGROUND
A specific phenotype of methimazole (MMI) induced malformations has recently been postulated. MMI embryopathy is characterized by minor dysmorphic features, choanal atresia and/or esophageal atresia, growth retardation, and developmental delay.


METHODS
We prospectively studied the outcome of pregnancy in 241 women counseled by 10 Teratology Information Services (TIS) of the European Network of Teratology Information Services (ENTIS) because of MMI exposure, and compared them with those of 1,089 pregnant women referred to TIS because of exposure to nonteratogenic drugs (control group). Information was obtained by mail or telephone interview.


RESULTS
There was no increase in the general rate of major anomalies or of spontaneous or induced abortions in the MMI-exposed group in comparison with the control group. Two newborns were affected with one of the major malformations that are part of the postulated embryopathy.


CONCLUSIONS
The results of this study indicate that choanal as well as esophageal atresia may have a higher incidence than expected in fetuses exposed to MMI between 3 and 7 gestational weeks. Until further data are available, thyrotoxicosis should be treated with propylthiouracil, as it is apparently safer for use during the fertile period.
Di Gianantonio
E
E
Servizio di Informazione Teratologica (SIT), Genetica Clinica ed Epidemiologica, University of Padua, 35128 Padua, Italy.
Schaefer
C
C
Mastroiacovo
P P
PP
Cournot
M P
MP
Benedicenti
F
F
Reuvers
M
M
Occupati
B
B
Robert
E
E
Bellemin
B
B
Addis
A
A
Arnon
J
J
Clementi
M
M
D000014:Abnormalities, Drug-Induced / Q000175:diagnosis*; D000022:Abortion, Spontaneous; D000328:Adult; D000367:Age Factors; D001835:Body Weight; D015331:Cohort Studies; D002658:Developmental Disabilities / Q000139:chemically induced; D004933:Esophageal Atresia / Q000139:chemically induced; D005060:Europe; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007255:Information Services; D008297:Male; D008713:Methimazole / Q000009:adverse effects*; D010641:Phenotype; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D013723:Teratogens; D013997:Time Factors
D013723:Teratogens; D008713:Methimazole