Unfortunately, many women are unaware that they are pregnant at this time (Sadler, 2009). Thus, the timing of exposure influences the outcome with potential teratogens. Thalidomide, for example, causes anomalies when exposure occurs between days 20 and 36 after fertilization. At this time, even a single tablet could cause a limb defect (Vargesson, 2009). Furthermore, the fetal warfarin syndrome—characterized by nasal hypoplasia, stippled epiphyses and growth restriction—is most likely to emerge after exposure between the 6th and 9th weeks of development. After this, warfarin may produce less severe anomalies (Goodwin et al, 2010).