 The right side of the heart, shown here in blue, pumps deoxygenated blood from the body to the lungs, where it can fill up with oxygen, and then the left side of the heart, shown here in red, pumps oxygen-rich blood from the lungs to the rest of the body. So blood travels from the body to the right side of the heart, to the lungs, to the left side of the heart, back to the body. But what if you're still in the womb? When you're a fetus, your lungs don't work, because they're filled with fluid. So how does your heart bypass the lungs and spread the oxygen-rich blood coming in through the umbilical cord to the rest of your body? Before we're born, we have an extra blood vessel, called the ductus arteriosus, that directly connects the right side of the heart with the left side of the heart, bypassing the fluid-filled lungs, until you're born and you take your first breath, and then this blood vessel closes. But in about 1 in 10,000 births, this blood vessel closes prematurely, while the baby's still inside, necessitating an emergency C-section. Most cases, for which there's a known cause, are thought to be related to taking anti-inflammatory drugs, like aspirin or ibuprofen. This is because the way your body keeps its blood vessel open is with a class of inflammatory compounds called prostaglandins. If you take an anti-inflammatory drug, you can undermine your body's ability to keep it open, and it could constrict closed prematurely. That's why most authorities recommend that these NSAID anti-inflammatory drugs be avoided in the Third Trimester. The likelihood at anything bad is going to happen is extremely remote, but better safe than sorry. Sometimes, the premature constriction happens even when women are not taking drugs, though, so-called idiopathic cases, which is doctor-speak, for we have no idea what caused it. Well, if anti-inflammatory drugs can cause it, though, what about anti-inflammatory foods? A few years ago, I profiled two cases, apparently caused by pregnant women drinking chamomile tea, one of which reversed. The ductus opened right back up once the tea was stopped, but the other baby had to come right out. Since then, there have been other case reports. For example, a woman who had been drinking a few ounces of an acai berry drink every day, or another woman who was drinking prune juice and a violet vegetable juice containing a blend of foods and veggies, pregnant women should therefore take special care when consuming lots of these powerful anti-inflammatory berry nutrients. What about berries themselves and green tea and all the other wonderful anti-inflammatory foods and beverages out there? This group of researchers in Brazil compared ultrasounds of Third Trimester babies' hearts inside moms who ate a lot of these anti-inflammatory foods compared to women who ate less, and they could tell the difference. The speed of the blood through the ductus in the anti-inflammatory diet moms was higher, suggesting it was narrower, just like when you pinch the opening of a hose closed and make water shoot out faster. And also the right sides of their hearts of the babies in the anti-inflammatory diet moms were larger than the left side, suggesting some blood back up, again an indicator of a tighter ductus. The researchers suggested changes in late pregnancy diets may be warranted, but critics replied that, the differences they noted may not have any clinical relevance, meaning it may not matter if the vessel is a little more open or closed. And look, we don't want to freak women out as many of these anti-inflammatory foods may be beneficial, like cranberries, for example, which may be useful in preventing urinary tract infections, which can be a risk factor for premature birth. So cranberries are an attractive public health and cost consideration standpoint, if it can prevent some of these premies from being born to early. So, before cutting down on healthy food like cranberries, we'd want some stronger evidence that they're potentially harmful. What about confounding factors? For example, maybe women who ate lots of anti-inflammatory foods had other characteristics that could affect fetal blood flow. What we would need is an interventional trial, where you take pregnant women, change their diets, and see what happens. But we didn't have such studies until now. And a few weeks during third trimester, cutting DAC on anti-inflammatory foods like tea, coffee, dark chocolate, grapes, and citrus did indeed seem to open the ductus a little bit. This was during normal pregnancies, and women whose fetuses had abnormally constricted vessels a few weeks of removing polyphenol-rich foods reversed the ductal constriction in 96% of cases. Now, importantly, they didn't follow these babies after birth to see if it made any difference. You know, that complete closure only happens at 1 in 10,000 births. We're not sure what effects just kind of relative levels of constriction may have. So, it's too early to be instituting a ban on dark chocolate for pregnant women. At this stage, we're left with just kind of a note of caution. So, during the rest of life, I recommend piling on these healthy foods like berries and cocoa powder. From about 28 weeks until birth, pregnant women may want to cut back until we know more.