Question: 26 yrs old G2 P1L1 at 6+2 wks of gestation by dates received inj Methotrexate 100mg for suspected ectopic pregnancy. Next follow up intra uterine gestation with yolk sac seen. What are the effects on fetus if pregnancy continues?
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Answer: The British National Formulary (BNF) (1) says methotrexate is teratogenic.
The “Drugs in pregnancy and lactation” reference guide (2) adds:
“The use of methotrexate during organogenesis is associated with a spectrum of congenital defects collectively called methotrexate embryopathy or the fetal aminopterin-methotrexate syndrome. The critical period of exposure is 6-8 weeks post-conception (8-10 weeks after the first day of the last menstrual period), and the critical dose is thought to be ≥ 10mg/week. Typical characteristics of the syndrome are IUGR, a marked decrease in ossification of the calvarium, hypoplastic supraorbital ridges, small, low-set ears, micrognathia, limb abnormalities, and occasional mental retardation.” (Evidence level III)
References:
- British National Formulary. March 2009
- Drugs in pregnancy and lactation: a reference guide to fetal and neonatal risk. 8th edition / GG Briggs, RK Freeman & SJ Yaffe. Philadelphia; Lippincott Williams & Wilkins, 2008.p 1176-83
Search date: June 2009
Classification of evidence levels
Ia Evidence obtained from meta-analysis of randomised controlled trials.
Ib Evidence obtained from at least one randomised controlled trial.
IIa Evidence obtained from at least one well-designed controlled study without randomisation.
IIb Evidence obtained from at least one other type of well-designed quasi-experimental study.
III Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies.
IV Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities.
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