Correctly managing pregnant patients vital to fetal care

WASHINGTON — A presenter at the annual American College of Physicians Internal Medicine Meeting stressed that the most important aspect of managing pregnant patients is understanding that maternal health comes first.

“Fetal well-being depends on maternal well-being,” Lucia Larson, MD, FACP, the director of the division of obstetric medicine at Alpert Medical School at Brown University, said in her presentation. “Most of the time, whatever is the best thing to do for the pregnant woman overlaps with what is best for the fetus.”

Physiological changes due to pregnancy

Larson, noting that pregnancy is a normal state, not a disease state, said that pregnancy triggers significant physiologic changes in a woman’s body in the first trimester. This includes respiratory changes such as minute ventilation increases and decreases in upper airway size, which can make intubation very difficult; hematologic changes, such as hemoglobin decreases and increased platelets and clotting factors; and renal changes, such as decreased creatinine and increased GFR and protein in urine.

The biggest implications, Larson said, are for the cardiovascular system, as pregnancy generates increases in blood volume, heart rate and cardiac output. Pregnancy can worsen known cardiac disease and unmask previously unidentified cardiac diseases.

“There’s some classic times when cardiac issues can present in pregnancy,” Laron said. “That includes when blood volume is peaking towards the end of that second trimester and you’re also at peak cardiac output at that time, so somewhere around 28 to 32 weeks and a woman comes in short of breath, that’s a classic time for issues to present. There’s also the work of labor and postpartum, when a lot of fluid shifts happen.”

Prescribing drugs to pregnant patients

Pregnancy also leads to altered pharmacokinetics, such as increased renal clearance, increased volume of distribution, altered absorption and altered protein binding.

“Everyone is afraid of using drugs in pregnancy because they’re worried about causing problems for the fetus, but actually, you need to use higher drug doses and more frequent dosing in pregnancy to get a therapeutic effect,” Larson said. “In my opinion, if we’re going to use a drug in pregnancy, we certainly don’t want to expose the fetus to a sub-therapeutic drug. We might as well get the therapeutic effect.”

She said that when using drugs in pregnancy, physicians need to have respect for the drug, but it is also critical to think about the risk of not using the drug, as that can sometimes do more harm.

Drugs may cause teratogenesis during the early stages or fetopathy effects later in pregnancy or even fetal withdrawal syndromes, Larson detailed. There is limited information on long-term effects of drugs in older offspring, so many experts prefer older drugs “with a longer track record.”

Risk for congenital anomalies is about 3% to 5%, with as many as 1% caused by drugs, chemicals or exogenous agents, she said. About 65% to 70% of birth defects have unknown etiology. In addition, 4% of congenital anomalies are from maternal metabolic disease.

Larson noted that the current FDA pregnancy risk classification for drugs is being phased out, because it has “serious limitations” and has “been misused.” She said that even though the categories are denoted by letter, the scale is not actually a grading system and does not help balance the risk-to-benefit ratio. A new system will be put in place in June that is more narrative in nature and will better help in decision making.

She also shared some of her favorite resources for drug prescribing, including Reprotox and TERIS, as well as resources for patients, such as Motherisk.

There are a lot of antimicrobials that can be used during pregnancy, including the favored penicillins and cephalosporins, as well as azithromycin and vancomycin, Laron said. In addition, antifungals, clarithromycin, trimethoprim and sulfonamides can be justified. Generally, tetracyclines and fluoroquinolones should be avoided, she said.

Diagnostic imaging

Larson explained that diagnostic imaging in pregnant patients is more than often perfectly acceptable.

“The horror stories about radiation are high exposures like Hiroshima, not diagnostic radiation,” she said. “We’re usually way more worried than we need to be.”

The National Council on Radiation Protection conservatively allows 5 rads of exposure in pregnancy, Larson said. Nearly all common diagnostic imaging involves radiation exposure well below 1 rad – a chest x-ray is <0.001 rads and head CT, chest CT and lung scans are also low. The greatest risk, she said, are the higher doses of radiation from abdomen CTs, which is direct radiation to the fetus, but still below 5 rads.

Diabetes in pregnancy

Larson stressed that hyperglycemia is associated with teratogenesis, and in women who do not receive preconception care, congenital anomalies can affect about 11% of babies. However, if a woman goes into pregnancy with a normal HbA1c, she faces the same rate of anomalies as the general population.

Physicians should focus on euglycemia as a treatment goal: the lowest HbA1c possible without hypoglycemia. Patients should test their blood for glucose at least four times daily and never before a meal.

Insulin is the gold standard for diabetic management of pregnant patients, Larson said, and it does not cross the placenta, and recommended analogues such as lispro and aspart. Long-acting analogues like glargine and detemir are more intense, but may be recommended for women who used them effectively before pregnancy.

Larson also said that glyburide is safe and effective for gestational diabetes, but does cross the placenta.

Preeclampsia

Larson acknowledged that preeclampsia is typically an obstetric disease, but internists are getting involved in atypical cases.

“Think of it like lupus – everyone’s is a little different,” Larson said. “It’s sneaky like that.”

She said that, according to American College of Obstetrics and Gynecology guidelines, preeclampsia can be diagnosed without proteinuria, as long as other symptoms exist.

It is important to achieve a goal blood pressure of 140-155/90-105 mm Hg, which can be done with hydralazine, labetalol or nifedipine.

Preeclampsia can cause a variety of issues including eye issues, seizure, stroke, pulmonary edema, left ventricular dysfunction, elevated liver enzymes, kidney failure, and diabetes insipidus.

Internists, especially, should be aware of associations between preeclampsia and cardiovascular disease, Larson said. When performing cardiac risk assessment, patients should be asked about any history of preeclampsia.

Preeclampsia is the leading medical cause of maternal mortality, Larson said. The most common error leading to death was a failure to diagnose venous thromboembolism, which occurred most often because of concern regarding radiologic testing.

Diagnosis can be difficult because clinical signs are unreliable, clinical decision rules such as Well’s criteria have not been validated in pregnancy and specificity of other testing in pregnancy is poor. A ventilation-perfusion scan is the diagnostic test of choice and ultrasound is the preferred test for leg studies. Both unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) have been established as safe treatments for pregnant patients; dosing increases with increasing gestation. – by Chelsea Frajerman Pardes

Reference:

Larson, et al. Challenges in Managing the Pregnant Inpatient. Presented at: ACP Internal Medicine Meeting; May 5-7, 2016; Washington, D.C.

Disclosures: Larson reported no relevant financial disclosures.