Critical periods of fetal development Human nutrition starts during pregnancy, the moment the fertilized egg attaches itself to the uterine wall and starts receiving nutrients from the mother. At the...

Extracted text: Critical periods of fetal development Human nutrition starts during pregnancy, the moment the fertilized egg attaches itself to the uterine wall and starts receiving nutrients from the mother. At the placenta, the mother and the embryo exchange nutrients, oxygen and waste. In this way, the embryo receives the nutrition it needs to grow, and allows the mother to handle the processing of waste. The nutrients received by the embryo depend on the nutrients consumed by the mother in her current diet, as well as those in her nutrient reserves. If the mother lacks nutrients, the embryo will lack them as well. Red blood cells, bacteria and large proteins in the mother's blood cannot pass to the embryo, but some potentially dangerous substances can. Alcohol, caffeine, illicit drugs, prescription and over-the-counter medications can cross the placenta barrier and enter the embryo. Environmental pollutants such as mercury, arsenic and lead can cross the placenta barrier too. Some of these substances can be found in the diet and/or accumulate in the body, thus the need to pay close attention to healthy habits before the pregnancy. The nutritional state and presence of toxins are most critical in the first 3-8 weeks of the pregnancy, as this is the period when the embryo lays the base for the development of main organs. The mother starts sharing nutrients and other substances with the embryo shortly after conception, even though the mother may not know if she is pregnant for another few weeks. Based on the information above, match the following facts an advisories. Focus on those that have the closest match. In 2011, 45% of pregnancies in the US were unintended [ Choose ] [ Choose ] Refined wheat flour is fortified with folic acid by law in order to prevent birth defects in the population Nicotine in smokeless tobacco can cross the placenta and affect the development of the nervous system Woman of reproductive age should be aware of mercury advisories in fish, even if they are not intending to get pregnant A woman who is obese at the time of conception has a higher risk of a pregnancy with birth defects Critical periods of fetal development occur during the first trimester Woman who are planning to get pregnant should not smoke. This includes Lack of folic acid during pregnancy may result in a type of birth defect called spina bifida not smoking smokeless tobacco. Woman wanting to get pregnant are suggested to achieve a healthy weight before conception Exposure to a famine during the first trimester of pregnancy carries more [ Choose ] risk to the fetus than exposure during the third trimester