← The OB/GYN Resident Survival Guide
The OB/GYN Resident Survival Guide
#23: Nausea & Vomiting of Pregnancy: Prevention, Management, and Something Called Neiguan's Point??
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Welcome back to the OBGYN Resident Survival Guide, a podcast with bite sized clinical pearls that you can consume on the run. I'm your host, Dr. Casey Miller and today we are going to be talking about nausea and vomiting in pregnancy. Before I jump in, if you are a fourth year medical student patiently waiting for the match but hoping and planning to start your OBGYN residency this July, I I put together an OB GYN Residency Starter pack with tips and resources to help you prepare for July 1st. If you don't want to jinx it, you can download it and save it for later after the match, but I will put the link in the show notes. It's free and doesn't take very long to go through so if you're interested, go and check it out. All right, let's jump in. Nausea and or vomiting of pregnancy affects about 50 to 80% of pregnant patients, so it's very likely that you will have to manage these patients in both the ambulatory setting and inpatient when people come to OB triage or when they're admitted to the antepartum service as a result of the severity of these symptoms. This condition, so to speak, exists on a spectrum, with nausea alone being on one end of the spectrum and then increasing to nausea and retching and then nausea and vomiting all the way to the more extreme end of the spectrum with hyperemesis gravidarum. And while there is no universally accepted definition of hyperemesis gravidarum, there are some commonly utilized criteria that can help us to make a diagnosis. So the first is persistent vomiting, not related to any other causes. So of course you need to do a workup to make sure there isn't some other underlying condition like gastroparesis, gastric ulcer, pyelonephritis, dka, et cetera going on. That is actually the etiology for the symptoms. The second criterion is evidence of starvation, which is typically identified by the presence of ketones on a urine dipstick. The last criterion is weight loss, specifically a weight loss of at least 5% of the pre pregnancy weight. In addition to what I just mentioned, there may also be evidence of electrolyte and endocrinologic abnormalities that support the diagnosis, although these findings are not necessarily required for a patient to meet criteria per se. So why does this happen? While we have a lot of theories, we don't actually have a complete understanding of the exact etiology for the nausea and vomiting that happens in pregnancy. But the primary idea is that these symptoms are secondary to the natural elevation of hcg and estradiol that occur as a result of the pregnancy, and this is supported by the finding of an increased incidence of nausea and vomiting and and hyperemesis gravidarum in patients with placental conditions that lead to an increase of hcg, for example Molar pregnancies and multiple gestation pregnancies like with twins, triplets, et cetera. Additionally, increased levels of circulating estradiol have also been shown to influence nausea and vomiting even outside of pregnancy. Think about how patients receiving IV estrogen for acute abnormal uterine bleeding or even estrogen in the form of combined oral contraceptives commonly experience nausea and vomiting as a side effect of these medications. Furthermore, circumstances where estradiol and HCG levels are decreased in pregnancy, for example cigarette smoking, have been associated with lower rates of hyperemesis gravidarum and interestingly, this has been identified in multiple studies. There's also a theory that evolutionary adaptation plays a role. If pregnant patients have food aversions and are more sensitive to smells and tastes, then they may be less likely to consume foods that could potentially harm them and their fetus. So it would make sense that this is an evolutionary survival mechanism of sorts. Now let's talk about management. I'm going to break it down into three categories prevention, non pharmacologic interventions, and pharmacologic interventions. So let's talk about prevention. First, there is evidence to suggest that the initiation of a prenatal vitamin at least one month prior to conceiving a pregnancy may reduce the severity and incidence of nausea and vomiting in pregnancy. So get them started on a prenatal at their preconception counseling visit if you happen to catch them before they actually get pregnant. Next, although there isn't much data to support specific dietary changes for prevention or management of symptoms, it is recommended to counsel patients to replace their larger meals with multiple small meals every one to two hours throughout the day to to avoid having a full stomach. Along the same line, replacing fatty and spicy meals with bland, specifically high protein foods may help as well. Lastly, avoiding sensory stimuli like extreme temperatures, strong fragrances, bright or flickering lights and overexertion may be beneficial for prevention of these types of symptoms. Now let's talk about the non pharmacologic interventions. The first option is going to be the replacement of iron containing prenatal vitamins with folate only supplements. A known side effect of oral iron supplementation is GI upset, so just take that out of the picture right out the gate. The second option you can consider offering are actually ginger supplements. Now, data is mixed when it comes to results. Some studies have shown a beneficial reduction in nausea, but not necessarily vomiting. There is also some data, again a little bit conflicting, but some data nonetheless, that supports the use of acupressure at Negin's Point just below the wrist. And this can be done with the use of commercial bracelets designed for this purpose. I read a little bit more about this and interestingly, these acupressure bands have also been studied for the management of chemotherapy induced nausea, also with mixed results. However, it seems like the breadth of available data is greater in these patient populations. But I have had some friends who were pregnant and really swore by those bracelets. So it'll be interesting to see if more data does come out in support of this or if it's just a placebo effect. Now let's talk about the pharmacologic interventions. So your first line intervention is going to be vitamin B6, otherwise known as pyridoxine, as well as doxylamine. And you can prescribe these as separate tablets or combination tablets. And depending on the formulation and the dose that you are using, you can start with either once a day at bedtime, up to four tablets per day. There's also evidence to suggest that in patients who have a history of nausea and vomiting in a prior pregnancy, starting the B6 and doxylamine before the onset of symptoms in the current pregnancy is more likely to reduce the symptom severity. If and when they do develop nausea and vomiting in the current pregnancy, your second line medications are going to be the dopamine antagonists and antihistamines. Probably the most commonly used dopamine antagonists are going to be promethazine, brand name Phenergan in the United States, Metoclopramide brand name Reglan, and prochlorperazine, brand name Compazine in the United States. Antihistamines include dimenhydrinate brand name Dramamine, and diphenhydramine, brand name Benadryl, although the unfortunate side effect of antihistamines, of course, is drowsiness. Now, all of these come in a variety of oral, IV and intramuscular formulations. However, the nice thing about promethazine or Phenergan is that it's also formulated as a rectal suppository, which can be a really great option for patients who can't tolerate pills but don't necessarily need to be hospitalized for IV or IM treatment. Now, it's important to remember that combining multiple dopamine antagonist medications, especially long term, can increase the patient's risk for for developing extrapyramidal symptoms like tardive dyskinesia and dystonia, so we should be trying to avoid those combinations when possible. Your third line medication is going to be the serotonin 5 HT3 receptor antagonist, primarily on Dansetron brand name Zofran. The nice thing about this medication is that it has an oral dissolvable formulation. So again for patients who can't swallow pills and who don't want a rectal suppository, they can pop the tab under their tongue and just let it dissolve. It is important to know that although this medication is being used more and more frequently in pregnancy compared with the first and second line pharmacologic options, safety data is still somewhat limited, particularly for use in the early first trimester during organogenesis. There is some evidence that associates use during the early first trimester with congenital anomalies. Most of the evidence does not show this association. Nevertheless, for this reason the ACOG does recommend discussing this with your patients before prescribing it for use if they are under 10 weeks gestation of pregnancy. Another thing to consider is that these medications can prolong the QT interval, especially in patients who already have underlying cardiac conditions or electrolyte derangements. So when possible we should be avoiding use in patients with this type of history and at a minimum try to avoid combining this medication with other QT prolonging medications. Our fourth line pharmacologic intervention is steroids, typically with methylprednisolone and or prednisone and usually in the form of a taper. Now there have been a few studies demonstrating a weak association between methylprednisolone use in the first trimester with oral clefts of the fetus. So until we have more data we basically try to save this as a last resort in patients who are less than 10 weeks gestation. Before I summarize, I do want to touch on tube feeds and parenteral nutrition. When a patient with hyperemesis has symptoms refractory to all or most of the interventions we've reviewed, they're requiring multiple hospital admissions for hydration, antiemetics, electrolyte derangements, et cetera, and they cannot maintain their weight. Sometimes we need to take things a step further and get nutrients to the patient by bypassing their mouth, meaning we put the food or the nutrition directly into the stomach or duodenum or directly into the circulation with an IV picc line. Enteral feeds with an NG tube is highly highly preferable to TPN with a PICC line. And it's unfortunate because a lot of people are not going to tolerate NG tube insertion and. And it seems like having a permanent IV line would just be the easiest, most convenient thing. Right. However, PICC line insertion and TPN use in pregnancy have a much, much higher risk of morbidity, specifically from thromboembolic events and sepsis from line infections. There's also some data, limited data, but data nonetheless, associating TPN use with adverse neonatal outcomes, although that needs to be better studied. But remember the Virtos triad? Way back from medical school, a pregnant patient is already in a hypercoagulable state. Then take someone who's so sick from vomiting all the time that they're losing weight constantly in the hospital, they're in a constant state of stasis, and then you put a central line in them, which itself alone, even in a perfectly healthy patient, has an increased risk for thromboembolism. It's just a bad combination. So if you have to bypass the patient's mouth, aim for tube feeds, coordinate with maternal fetal medicine and probably gi, and keep TPN off the table as an absolutely last resort. All right, let's review. Nausea and vomiting of pregnancy affects 50 to 80% of pregnant patients. And although we don't have a complete understanding of why it happens, we think it's related to elevated HCG and estradiol levels in pregnant patients. It's also possible that food aversion is a result of evolutionary adaptation to keep moms from eating and drinking substances that could potentially harm the pregnancy. Preventative strategies include starting a prenatal vitamin at least one month prior to conception and eating frequent small meals throughout the day that are bland and high protein. If a patient experiencing symptoms is taking a prenatal vitamin, the first step is to discontinue the prenatal and replace it with a folate supplement and discuss the possible benefit of ginger supplementation and or acupressure wristbands. If these interventions are not successful, your first line pharmacologic therapy is going to be the initiation of vitamin B6 and doxylamine. Your second, third and fourth line meds include dopamine antagonists like promethazine, prochlorperazine and metoclopramide, antihistamines like dimenhydrinate and diphenhydramine, serotonin 5ht3 receptor antagonists like zofran, and then steroids such as methylprednisolone and prednisone when patients are requiring multiple hospitalizations and are unable to tolerate any oral intake or maintain their weight, consider enteral tube feeds. TPN via a PICC line should be an absolute last resort due to the significantly increased risk of morbidity secondary to line infections and throw thromboembolism. That's it for today. Per usual, references are listed in the show notes, as is the residency starter pack. Take care and I will see you next week.