Mercury exposure can affect a developing baby's brain and nervous system, but this is mainly with non-commercial freshwater fish. In other words, Charlie the Tuna in a can isn't a problem, but the recreational or freelance fisherman's catch of the day could be, and that may apply to many restaurants. The EPA recommends having only a six-ounce portion of fish once a week, but just as there is no safe level of alcohol consumption established, I think the same can apply to a known, nasty toxin like mercury.
For those who really want to eat more fish than this, each state has a website that will report on the levels and toxic risks of the fish in its area.
BOTTOM LINE: Mercury is just too scary to eat fish whenever you want. Obey the EPA's recommendations.
We're talking about Listeriosis, a bacterium ingested with certain foods, which can hurt or even cause death in an unborn baby. Although cheese is the most famous culprit, any undercooked meats, unwashed vegetables, unpasteurized milk, or products from unpasteurized milk can give a dose of this infection.
The CDC has an excellent website for all things listeria. In general, though, you should cook all animal meat thoroughly. Wash all vegetables and stay away from unpasteurized products. Also, keep your countertops clean. An unwashed vegetable laying on the counter, then washed, then put back on the counter could reclaim the Listeria. Eat deli meats that have been reheated steaming hot.
And here's the cheesy part you've been waiting for: According to the CDC, you should "avoid soft cheeses, like feta, Brie, Camembert, blue-veined cheeses, and Mexican-style cheeses such as queso blanco fresco. Cheeses that may be eaten include hard cheeses, semi-soft cheeses such as mozzarella, pasteurized processed cheese slices and spreads, cream cheese, and cottage cheese."
Sports and Exercise
Any sport that doesn't involve blows or falling down is fine in pregnancy. Exercise is fine, as long as you don't have any pre-pregnancy conditions that would make it dangerous, like heart conditions; as long as you're not high-risk, as with preterm labor; and as long as you proceed in a reasonable way.
SCUBA diving, although I have nothing scientific to back this up, would be on my list of things to make me nervous as an obstetrician. There must be a reason no one is pushing pregnant women into hyperbaric oxygen chambers. Also, metabolism is altered such that the usual formulae for oxygen consumption from SCUBA gear may have to be adjusted. Skydiving? As long as you're not so high up that you need oxygen, your parachute has been packed properly of course, and you know how to land, skydiving is OK. (For that one reader out there who skydives while pregnant—this was for you.)
Even with the good news that almost all exercise is fine, even desirable, in pregnancy, any sports that involve sprinting or sudden load demands on joints may be more likely to cause orthopedic injuries then when not pregnant. Your center of gravity is different and progesterone loosens all of your joints, but it's impossible to tell how much impact this will have on a sportsperson.
Horse back riding—another jolting experience. Usually the added discomfort of pregnancy will stop an equestrian before her doctor will.
BOTTOM LINE: Sports—have at it. SCUBA with caution. Don't do kick-boxing. Scratch that one off your list.
You have enough hormones already, but there are times when your obstetrician may use more. Micronized progesterone, identical to the same stuff the placenta makes, is used to support first trimester pregnancies that are in danger of miscarriage. There's debate as to whether it does any good, but I for one feel it does no harm. Lately there's been talk of giving it to control preterm labor, because it relaxes muscles. This will probably be an important addition to the management of preterm labor in the near future.
Estrogen isn't given in pregnancy. If you've been taking birth control pills by accident (that is, before you knew you were pregnant), although this has a theoretical risk, I've never seen this hurt a baby. Just don't do it on purpose.
Testosterone and anabolic steroids can hurt your baby, especially if female. Virilization (male-like) effects can occur.
BOTTOM LINE: Progesterone is safe. Other hormones can be harmful unless exposure is minimal and accidental
Amusement Park Rides
Amusement park rides which alter gravity in intensity and in sudden direction changes could theoretically cause placental tearing with horrible consequences. I've never seen a case, but I don't want to, either.