We often talk about how tea is one of the healthiest beverages you can drink. Tea is full of great nutrients, antioxidants, and other beneficial compounds. It's a way to drink more water without having to just drink water. It's calming and energizing and can even help you with weight loss.
There's just one exception: pregnancy.
When you're pregnant, your body is put under extreme changes, as it adapts virtually every system to the sole task of forming and nourishing a child. Your bodily needs change, and your cravings change to suit those needs, though you might not always know how to interpret them.
More importantly, your body reacts differently to certain chemicals. They might interact with hormones, they might increase the risk of birth defects, and they might even trigger pre-term labor. With so much at stake, it's better to be safe than sorry, right?
The Big C
The first and most obvious potential issue that you can find in tea is the big C: caffeine.
When your body is dedicating all of its energy to pregnancy, it's easy to decide you want to get some energy from an outside source. You've likely heard that caffeine is to be avoided as much as possible. It increases blood pressure and heart rate, and as a diuretic it reduces bodily fluid levels, leading to dehydration. 
Caffeine can also cross the placenta to affect the baby in development. Remember that you have built up a lifetime of caffeine tolerance, but your developing child has not. An amount of caffeine you wouldn't even notice might be extremely impactful to a fetus.
Caffeine can also cause birth defects, premature labor, and low birth weight delivery, among other issues.
Now, caffeine is all over the place. Coffee is the most common offender, but it's also present in chocolate, sodas of course, and even many teas. While a standard cup of black coffee might have 100-200 mg of caffeine, tea is much less. Even still, it's enough to be detrimental.
Black tea, green tea, oolong tea, white tea, and puer tea all come from the same plant, and thus all have caffeine in them. The amount of caffeine varies depending on the type of tea, with white tea having the least and black tea the most, in general.
Matcha should also be avoided, because it's just green tea but stronger. Likewise, purple tea is a crossbreed of the traditional tea plant, and has caffeine in it as well.
What this basically does is limits you to only herbal and rooibos teas. That's not all, though; you also have to look at the effects of herbs and additives in your tea blends. Not all natural plants are healthy for a pregnant mother.
When you're looking at herbal tea blends, even decaf teas, be aware that they may include other ingredients that are synonymous with caffeine. Cola leaf, guarana, mate, yerba mate, kola nut, guayusa, and a few other plant-based ingredients are all just different ways marketers can say there's caffeine in their products without actually disclosing that there's caffeine in them.
Other Herbs to Avoid
Many of the herbs we're going to list below are safe in small amounts. One cup of tea in a day is probably fine. Two may also be fine. Three or more may start causing problems. As such, you should either cut back on the tea you're drinking, brew it lighter to infuse less potentially damaging chemicals into your tea, or both.
Peppermint can be potentially damaging to pregnant mothers. It can cause mild uterine contractions, which normally don't matter much, but can be dangerous in the first trimester. Again, drinking a single cup each day probably won't be too bad, but drinking much more than that on a regular basis can be detrimental. It's generally best to avoid peppermint tea in the first trimester entirely, and limit it in the second and third.
Chamomile is typically used as a very mild sedative. It helps you relax and calms you down, and it can be used as a sleep aid that is much less active than sleep-inducing medications. It also has antioxidants and nutrients that help boost the immune system to fight off illnesses.
Unfortunately, all of those benefits might be outweighed by the potential drawbacks. The anti-inflammatory properties of chamomile might be disruptive to pregnancy, though as of yet there aren't any firm studies to say what their effects may be. Some people believe it might also induce early labor the way peppermint tea can, but there's not much data about it to say for sure.
Licorice is one that you should avoid altogether. Specifically, tea made from the licorice root is best avoided. It includes chemicals that are estrogenic, which can lead to both preterm birth and birth defects.
Note that Star Anise, an herbal spice that has a fragrant licorice scent, is safe in small doses. However, there's a risk with star anise. There are two varieties; Chinese and Japanese. Chinese star anise is the safe spice we use all the time. Japanese star anise is poisonous and can harm both you and your developing child. There's no way to tell them apart without chemical analysis, unfortunately, so consume it in moderation or avoid it if you're wary of the risks.
Raspberry Leaf is another tea ingredient you will want to avoid while pregnant. The leaves of the red raspberry plant are packed with beneficial nutrients and have been used for centuries to treat a variety of ailments.
Much like peppermint, raspberry leaf can induce contractions. It's generally recommended that you avoid it during the first trimester as much as possible. Conversely, some people recommend drinking it near the end of the third trimester, to help ease labor when it comes or induce it if it's time. Additionally, it's good to drink after birth to help restore calcium and augment breastfeeding.
Cohosh, of both the black and blue varieties, are herbs that are generally used as herbal medicines. It is often used to treat female-specific symptoms such as menopause, PMS, and for inducing labor. As with other herbs with labor-inducing effects, you want to avoid this during the early months of pregnancy, but it can be fine or even beneficial in the later months.
Additional herbs may have a wide variety of potentially negative effects. Most of them are safe when consumed in limited quantities, such as 1-2 cups of tea per day. Since most tea additives are in relatively small amounts, and brewing the tea further limits the amount of those chemicals you receive, it's not to terrible to consume them occasionally.
For a more robust list of what herbs you should avoid, check this page. It has a great table of common and uncommon tea additives and blends that you should watch out for.
Teas You Should Drink
Some teas can be beneficial while pregnant, at least in small doses, but potentially dangerous in larger amounts.
For example, ginger tea can help with morning sickness and general nausea, the same way a ginger ale might. Ginger can help with nausea, vomiting, and uterine cramping in early pregnancy. It's good to drink a cup when necessary, though if you find yourself drinking three or more every day, dial back.
Lemon Balm is a safe herb you can drink in moderation as well. It can be similar to chamomile, in that it helps reduce stress, relax your body, and lower anxiety levels. It's not as potent as chamomile, but that's why it's safe. It can help ease your sleep and help you sleep longer as well.
Rooibos in general is a good base for teas you can drink. Unlike traditional tea plant teas, rooibos does not have caffeine in it unless another additive has included it. If you're not usually a rooibos drinker, you may need to adjust to get used to it, but it's a fantastic base for certain otherwise-herbal teas.
Rooibos contains magnesium and calcium in high amounts. During pregnancy, this is a good way to help with digestion issues and acid reflux. It also has antioxidants, and we all know how beneficial those can be.
Nettle tea is considered safe in some circles, but detrimental in others. As usual, it depends on how much you're drinking. Nettle includes iron, magnesium, and calcium, which are all beneficial to both you and the developing child. On the other hand, when consumed in large quantities, nettle can have several negative side effects. As usual, it's generally best to limit yourself to one or two cups of nettle per day.
Make sure that you're getting nettle leaf, specifically, and not nettle root or just a blend of the whole nettle plant. The root doesn't have as many health benefits and has worse side effects.
Dandelion is another common tea ingredient that is only beneficial later in your pregnancy. It has a mild diuretic effect, which means you're going to want to make sure you're staying hydrated whenever you're drinking it. It's often recommended for later in your term because you may start experiencing fluid retention, at which point a diuretic can help you balance back out.
Fruit teas can help to bridge the gap between drinking tea and drinking some kind of juice. Juice, as a much stronger flavor, is occasionally preferable when you're not sure what else you want to be drinking. However, many juices – unless you're making them yourself – include a huge amount of added sugar from their processing. Drinking a fruity tea can help give you the fruit flavors you want without drinking too much sugar.
Rose hips is a great addition to a lot of herbal tea blends. It is one of the better herbal sources for vitamin C, which helps to boost your immune system and is used throughout the body to keep you healthy.
A Final Note
One thing that you may discover while researching this topic is that some people will say one ingredient is terrible and should be avoided at all costs, while others tout the benefits of the same ingredient for a healthy pregnancy. Raspberry leaf is one such ingredient; some sites claim it's best avoided, while others promote it as a great option to drink.
The fact is, pretty much all teas are going to be fine in moderation. Drinking one to three cups of tea per day, no matter what the blend is or how strong you brew it, is probably going to be fine. Maybe the strongest, most highly caffeinated tea you can find will be detrimental, but even then it's only on par with a cup or two of coffee. 
The biggest key to keep in mind is that teas are not necessarily a well-regulated industry. You want to make sure you trust the place you're getting your tea, and make sure they're getting their ingredients – whether it's raspberry, nettle, green tea, or cinnamon – from a legitimate source.
The largest risk with drinking herbal teas is drinking them when they are contaminated with a more dangerous substance. Whether this means the herb in question was grown using pesticides or if it a mix-up with the wrong type of star anise doesn't matter. What matters is that you know what you're taking into your body.
Personal experience time! We want to know what your experiences have been with teas during pregnancy.
Have you moderated your consumption at all, or have you just kept on keeping on with your tea habits, and how has it made you feel? If you've had more than one pregnancy and done something different each time, we'd also like to know how those changes affected you. Let us know your story below!
