## First trimester (weeks 1-13 of [pregnancy](https://ul.orna.me/KOge/librarydisease?id=3)) During this period, the immune system of a woman is reduced, there is a global restructuring of all the processes in the body, and medications have the strongest influence on the future child. In the event of incompatibility with life abnormalities occurring in the embryo in the first 4–5 weeks of development, in most cases, there is a miscarriage. Doctors recommend avoiding any medications during this period, except those prescribed to the mother for vital indications. However, you should not worry if you have taken something before you know you are pregnant. If the pregnancy is developing the baby will most likely not be affected in any way. It is a shortlist of medications that have been proven to be harmful in the first trimester, and they include: __Isotretinoin__, often found in acne products, can lead to malformations. __Anti-fungal drugs__ based on fluconazole increase the risk of miscarriage. __Medications from the benzodiazepine group__ increase the risk of cleft palate in the baby. __Antihistamines__ in the first 9 weeks are dangerous because histamines are important for the correct formation of the baby's organs and the adjustment of metabolic processes between mother and baby — if the expectant mother suffers from severe seasonal allergies, it is better to change the place of residence before the flowering ends as well as limit contact with allergens that the mother has had reactions to. __Antibiotics from the tetracycline group__ may have a negative effect on the formation of the baby's teeth. __Aminoglycosides__ can affect a child's hearing, up to and including deafness. __And fluoroquinolones__ increase the risk of bone abnormalities. However, there are antibiotics that can be taken by pregnant women in the first trimester in cases when "the potential benefit is greater than the potential risk." Each specific situation should be considered individually and discussed with a doctor. ## Second trimester (weeks 14-28 of pregnancy) At this time, the liver bears an increased burden: after the 14th week, the baby's liver starts producing its own bile and the pancreas starts producing insulin. Doctors say that 20 % of the mother's liver and pancreas work for the baby at this point. Since many medications load the liver, in the second trimester it is very important to discuss with the doctor each drug and carefully monitor the dosage. The list of prohibited drugs is, however, reduced: you can take antihistamines, analgesics, and antipyretics for fever over 100 °F. However, vasoconstrictor drops are forbidden, as their regular use may cause an increase in uterine tone. This increases the risk of premature birth due to contractions, which start at the 20th week. ## Third trimester (weeks 28-40 of pregnancy) Most of the discomfort in this trimester is physiological and does not require treatment. For example, blood volume increases by 40–50 %, so the heart beats more frequently. Heartburn is related to the fact that the enlarging uterus presses on the stomach. The shift in the center of gravity in many people causes back pain. Additionally, you can take an antacid for heartburn or a painkiller if your back is aching. Mothers are always advised to seek medical consultation with their doctor before taking any new medications.