just as we can foster weight-gain microbes through a poor diet, we can promote the growth of beneficial microbes through a healthy diet. Although scientists haven’t identified specific microbes associated with leanness yet, it has been shown that a varied diet that includes fruits, vegetables, and fiber promotes a diverse microbiota, a characteristic of lean (and healthy) individuals. Thus, you, and your microbiota, are what you eat—and there is probably no better time to watch your diet than when you’re pregnant. Bad dietary choices during this stage of life will not only make women gain more weight than what is considered healthy, they also have the potential to influence a child’s future ability to control weight. So, next time you walk by a candy machine, don’t listen to your sugar-loving microbes, and nourish the trillions of microbes that are begging you to grab a piece of fruit instead.
The Vaginal Microbiota
During pregnancy, microbiota adaptation also occurs in the vagina, an organ that hosts millions of microbes. The composition of this microbiota influences vaginal health tremendously. Many women develop yeast infections after being on antibiotics or oral contraceptives (birth control pills alter the pH of the vagina). Bacterial vaginal infections, also known as vaginoses, are very common. These infections occur when yeast (often Candida) or bacteria overrun a beneficial group of microbes known as Lactobacilli, a type of lactic acid bacteria that is very common in the vagina. Lactic acid bacteria are also used in the dairy industry for the production of yogurt, kefir, cheese, and buttermilk. Many of them have health benefits and are used as probiotics.
During pregnancy, the number of vaginal Lactobacillus increases dramatically, which is thought to occur for two important reasons. First, by keeping the vagina acidic, the presence of Lactobacillus helps discourage disease-causing microbes such as E. coli, which do not like to grow in acidic conditions. There’s probably no better time to arm the bacterial vaginal defenses than during pregnancy, when a pathogen could track up from the vagina, through the cervix, and into the uterus, where the baby is growing. In fact, it is known that certain vaginal infections during pregnancy are associated with preterm and low-weight births. Second, Lactobacilli are great at digesting milk, as their name suggests (lacto is Latin for “of milk,” and bacillus is the name given to rod-shaped bacteria). By ramping up the levels of Lactobacillus in vaginal secretions, more of these bacteria will reach the baby’s gut (when born vaginally), and facilitate the digestion of the only food the baby will eat for months: her mother’s milk. In this sense, Lactobacilli are probably a baby’s first and best microbial friend.
The vaginal microbiota plays a very important role during pregnancy and birth, as it is one of the sources (along with the gut microbiota) of the first microbes to set up camp in a newborn. As soon as a baby is born vaginally, she gets covered in vaginal secretions and, yes, with fecal matter, too. Consequently, the composition of vaginal secretions is of utmost importance during pregnancy, and vaginal health should be taken very seriously during this period of time. Just as women should take care of their diet to promote a healthy intestinal microbiota, they should look after their vaginal health, too.
To promote vaginal health, gynecologists recommend that pregnant women wear cotton underwear, avoid vaginal douching (never recommended), avoid vaginal cleaning products, and use gentle, unscented soaps to clean the outside of the vagina only. The vagina is an organ that cleans itself through the production of secretions and needs little extra hygiene. In fact, cleaning the interior of the vagina is strongly associated with infections, as it alters the balance of the resident microbiota. In addition, it has been shown that the consumption of probiotics containing Lactobacillus acidophilus decreases vaginal infections. Several clinical studies suggest that eating yogurt may help, too, although not to the same extent as probiotics alone. You can even get probiotic preparations in the form of vaginal suppositories, which are used to treat such infections. Safe sex is the best way to avoid sexually transmitted infections (STIs); it is a practice that should always be followed, and especially during pregnancy. An STI contracted during pregnancy can be more dangerous to the mother than an STI contracted at another time, as immune systems are weaker during pregnancy—a physiological adaptation meant to prevent a woman’s immune system from reacting to the fetus. Unfortunately, this makes a mother-to-be more vulnerable to infection.
Stress, Your Baby, and Your Microbes
Another important measure to maintain a balanced microbiota during pregnancy is to avoid stress, which is always easier said than done. We’ve all felt it—stress is a condition that affects most people at some point or another. It can be helpful sometimes, like when it compels you to finish an assignment for work that’s due the next day. The problems arise when stress becomes an everyday companion; this is when it affects our health. Stress can make you lose sleep, have headaches or stomachaches, overeat, or lose your appetite. While pregnancy is typically a very joyful time, it can also be difficult. Dealing with the physical discomforts such as nausea, exhaustion, and backaches may quickly add up. On top of that, hormonal changes affect mood and the ability to handle stress.
A moderate level of stress is unlikely to cause a major impact on the health of a mother or her baby. However, certain situations may lead to severe stress, which can have detrimental effects on the pregnancy and the health of the baby. Abrupt negative life events, such as divorce, serious illness, financial problems, partner abuse, depression, and the conflicting feelings surrounding an unplanned pregnancy—to name a handful—are all causes of long-lasting or severe forms of stress. Some women suffer severe stress and anxiety when faced with the idea of labor or parenting. Severe stress is associated with preterm and low-weight births, and with certain illnesses in children, including skin conditions, allergies, asthma, anxiety, and even attention-deficit hyperactivity disorder (ADHD; see chapter 14).
A recent study from the Behavioural Science Institute of Radboud University, in the Netherlands, suggests that the microbiota plays a leading role in the link between stress during pregnancy and the aforementioned disorders. This study, which recruited fifty-six pregnant mothers, found that women who experienced high and prolonged levels of stress had alterations in the vaginal microbiota that could also be detected in their babies’ gut microbiota. Infants born to highly stressed mothers showed lower levels of beneficial microbes, such as lactic acid bacteria. In the same study, these changes to the microbiota were associated with more gastrointestinal issues and allergic reactions in babies. They also found that the negative effects of severe maternal stress could not be corrected by breastfeeding, even though it has been repeatedly shown to promote a healthy microbiome in infants.
A similar study aimed at exploring the link between maternal stress and the microbiota was recently performed in mice. The study showed that a reduction in vaginal lactic acid bacteria, caused by stress, is accompanied by decreased immune functions in the offspring. Furthermore, the changes in the baby mice were not limited to the types of bacteria growing in their guts; there were also important metabolic differences detected in their blood and their developing brains. It may well be that the vaginal microbiota is at the center of this, responding to maternal stress and transferring its imbalanced state to the newborn, where it can lead to lasting health consequences. Although a casual relationship remains to be established, it appears that lactic acid bacteria from vaginal secretions are not only involved in facilitating milk digestion in newborns, but also carry out important metabolic functions in the developing newborn—yet another reason to reduce stress as much as possible and to take daily probiotics during pregnancy.
Infections and Antibiotics: Can We Avoid Them?
Controlling your diet and your stress levels during pregnancy is an enormously challenging goal for most women, but it can be done. However, the microbiota of pregnant women can suffer a big blow through a situation that’s out of their control: taking antibiotics to treat an infection. As mentioned before, pregnant women are more vulnerable to infections, and if they occur, they are likely to be more severe due to their compromised immune systems. This is why it’s recommended that pregnant women wash their hands often, avoid caring for people with infections (good luck with that when you have other kids!), avoid gardening without gloves, cook meats thoroughly, avoid changing the cat litter box, and avoid deli meats, sushi, and unpasteurized milk. Pregnancy is definitely