They do, however, list several circumstances when a woman should contact her healthcare provider before continuing with an exercise program: vaginal bleeding, dyspnea before exertion, dizziness, headache, chest pain, muscle weakness, preterm labor, decreased fetal movement, amniotic fluid leakage, and calf pain or swelling (to rule out thrombophlebitis). Sleep
It has been suggested that shift work and exposure to bright light at night should be avoided at least during the last trimester of pregnancy to decrease the risk of psychological and behavioral problems in the newborn. Dental care
The increased levels of progesterone and estrogen during pregnancy make gingivitis more likely; the gums become edematous, red in colour, and tend to bleed. Also a pyogenic granuloma or "pregnancy tumor", is commonly seen on the labial surface of the papilla. Lesions can be treated by local debridement or deep incision depending on their size, and by following adequate oral hygiene measures. There have been suggestions that severe periodontitis may increase the risk of having preterm birth and low birth weight; however, a Cochrane review found insufficient evidence to determine if periodontitis can develop adverse birth outcomes. Flying
In low risk pregnancies, most health care providers approve flying until about 36 weeks of gestational age. Most airlines allow pregnant women to fly short distances at less than 36 weeks, and long distances at less than 32 weeks. Many airlines require a doctors note that approves flying, especially at over 28 weeks.
On the other hand, drugs like thalidomide with proven fetal risks that outweigh all benefits are classified as Category X. Recreational drugs
The use of recreational drugs in pregnancy can cause various pregnancy complications. Alcoholic drinks consumed during pregnancy can cause one or more fetal alcohol spectrum disorders. According to the CDC, there is no known safe amount of alcohol during pregnancy and no safe time to drink during pregnancy, including before a woman knows that she is pregnant. Tobacco smoking during pregnancy can cause a wide range of behavioral, neurological, and physical difficulties. Smoking during pregnancy causes twice the risk of premature rupture of membranes, placental abruption and placenta previa. Smoking is associated with 30% higher odds of preterm birth. Prenatal cocaine exposure is associated with premature birth, birth defects and attention deficit disorder. Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities. Short-term neonatal outcomes in methamphetamine babies show small deficits in infant neurobehavioral function and growth restriction. Long-term effects in terms of impaired brain development may also be caused by methamphetamine use. Cannabis in pregnancy has been shown to be teratogenic in large doses in animals, but has not shown any teratogenic effects in humans. Exposure to toxins
Intrauterine exposure to environmental toxins in pregnancy has the potential to cause adverse effects on prenatal development, and to cause pregnancy complications. Air pollution has been associated with low birth weight infants. Conditions of particular severity in pregnancy include mercury poisoning and lead poisoning.