1 Rheumatology, Frimley Park Hospital, Frimley, 2 National Teratology Information Service, Newcastle, 3 Rheumatology, St Peter's Hospital, Chertsey and 4 Rheumatology, Royal London Hospital, London, UK
Correspondence to: M. Lloyd. E-mail: mark.lloyd{at}fph-tr.nhs.uk
SIR, We read with interest the report by Kinder et al. [1] of a patient who conceived while on methotrexate. However, we were concerned that our conclusions may have been misinterpreted. Our review [2], which was the largest of its kind at the time, concluded that exposure to methotrexate in pregnancy is associated with a roughly 25% risk of fetal malformation. We were not able to conclude that there is a threshold dose at which methotrexate is safe in pregnancy, partly because the numbers of cases of fetal exposure below 10 mg weekly are so few. This conclusion came from other authors and remains speculative [3, 4]. The National Teratology Information Service (NTIS) has a report of a pregnant woman who received a single dose of methotrexate 7.5 mg between 4 and 7 weeks of gestation. An emergency Caesarean section was performed at 28 weeks for placenta praevia and the baby had a number of abnormalities, including positive sweat test, ileal perforation and respiratory distress syndrome.
We would advise contacting the NTIS in any case of methotrexate exposure during pregnancy.
The authors have declared no conflicts of interest.
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