Because if it was done in late 1900s, the credibility of the research might not have been too great because it was illegal and in all states in the United States therefore, conducting a research on that topic and finding participant would have been quiet difficult. The first article, Marijuana use and its effects in pregnancy, was written in 2016 and the other article, Marijuana in pregnancy, was written in 2004. The first article, Marijuana use and its effects in pregnancy, suggest that there are not any effects on fetus and the mother while the other article, Marijuana in pregnancy, suggest that there are increased risk of complications. To confirm that time frame of the research does make difference, one of the books, obstetric medicine, also agrees with the first article that "maternal marijuana use has little or no effect on the fetus"