I'm not an elite runner by any stretch of the imagination. I'm a 2-3 miles a day-er, and I haven't run competitively since high school. However, running while pregnant (as I've been doing since first trimester) isn't about speed, mileage, or racing. And it requires some degree of thought and planning that running wouldn't otherwise entail. With that in mind, here are some things I've found helpful thus far (30 weeks tomorrow).
Pregnancy itself requires roughly 75 grams of protein daily according to the WHO. Protein requirements for running increase with mileage, but are estimated to be comparable if not greater than that for pregnancy for those who are training consistently. Runner's World recommends 75-120 grams per day. While their recommendations may be a bit high for those of us running only a few miles at a time, the point remains : an increase in dietary protein intake is a non-negotiable component of running while pregnant. I generally shoot for at least 80 grams per day, and haven't had any issues thus far. If anything, I think I've gained muscle because my diet was lower in protein than it should have been pre-pregnancy.
Excellent Sports Bras
Most women go up at least a cup size or two while pregnant, and let me tell you - that much growth in a short period of time is not comfortable. Neither bouncing nor throbbing are conducive to an enjoyable run! I went from an A to a C, and run in either a sports bra with an underwire, or two regular ones. I'm a fan of this one (above) for doubling up because it's fairly supportive and not bulky and also not expensive.
Maternity Workout Attire
Maternity workout - specific attire isn't necessary (tends to be expensive and a bit silly in my opinion), but a few seasonally - appropriate maternity shirts and a few pairs of shorts or pants in a larger size are a good idea. Since the majority of my pregnancy has been during warm weather, I generally run in one of these tank tops and a pair of non-maternity running shorts a size up from what I wore pre- pregnancy.
Good Running Shoes
For the average (non-pregnant) runner, the impact of each stride is roughly seven times his or her body weight. A healthy pregnancy involves weight gain, which can increase strain on joints. Further, a pregnant body produces a hormone called relaxin, which causes joints to be looser than normal (to allow for childbirth). Thus, pregnant running is running with 'weaker' joints under more strain than usual. This isn't necessarily a problem, but well - fitting shoes in good condition are a must to absorb some of the impact on the joints and to reduce the likelihood of injuries related to improper running form. I'm all for running in shoes with minimal support and for perfecting one's form, but pregnancy is not the time to do it. Go to a running-specific store, take an old pair of running shoes (so they can make recommendations based on your wear pattern), and be prepared to spend $70+. Target makes great shoes for chasing the kids around the yard or for low-impact exercise, but they're not suitable for running under 'extenuating circumstances.'
Maternity Support Belt
It's not necessary for the entirety of pregnancy, but may be useful towards the end (heavier, larger bellies are harder on the lower back, and thus more likely to affect one's running form). I bought the Gabrialla Belt around 28 weeks, and I haven't run without it since. It's also proven quite useful for work, since I spend 8-9 hours on my feet a day (cuts down on the tendency towards 'swaybacked and waddling' towards the end of the shift!).
Stretching (before and after)
It's probably a good thing to do regardless, but it definitely helps get the body warmed up for a run. Choose stretches that target your back and legs, since both are under more stress than usual. And hey - thanks to the aforementioned relaxin, stretching can be more fun than usual. Don't push joints too far, but don't be surprised if they seem slightly more flexible than before. Supposedly, flexibility gained during pregnancy can be retained postpartum if a stretching regimen continues after birth. I plan to give this idea a test run once I have the chance (as in, once I have this baby!).
Other Assorted Tips...
Overheating while pregnant can be dangerous, so I generally limit myself to running when it's below 80 degrees Fahrenheit. And I've made a point of stopping every mile or so to stretch and make sure I'm not getting too hot since early second trimester - this may or may not be necessary, but I'm sticking with it at this point. Running when the sun is not out definitely helps avoid overheating as well. Tangentially related to the issue of overheating, yes - I have run in only a sports bra while pregnant on warmer days. It garners a lot of weird stares, but take comfort in knowing that a pregnant body is nothing to be ashamed of (alternately, seek comfort in the fact that there are far scarier and more scantily - clad bodies to be seen at any public beach or pool!)
For most runs, sunscreen is a great idea. Pregnancy leaves the skin more susceptible than usual to hyper-pigmentation, which is exacerbated by sun exposure. I hate sunscreen, so I generally opt for vampire runs (running before the sun rises or after it sets).
A lot of websites recommend running with a water bottle while pregnant, though I've never done so. I hate carrying anything, and drinking water immediately before or during a run tends to make me feel sloshy and heavy. And then there's the issue of where to pee when you're dripping sweat and a mile and a half from home... Drinking plenty of water in the few hours leading up to a run has proven adequate in my experience.
On the issue of 'where to pee' though - plan your route with at least a few potty options, and don't be shy about asking to use a restroom if there isn't a public one. Fast food restaurants are good options, and even smaller businesses are highly unlikely to turn away a pregnant woman in need of a toilet! I've peed at the Mercedes-Benz dealership, at AutoZone, at mom&pop hardware stores, in the CVS employee restroom, etc...