Cholesterol and Pregnancy: What You Need to Know

We touched the topic of cholesterol last winter in the story about protecting your heart with a pregnancy diet rich in oils from fish, especially salmon, but you may be wondering about cholesterol in the broader health context as it related to pregnancy and the post-pregnancy years. Cholesterol is a very important lipid, a class of biochemicals that dissolves in oils, but does not mix well with water. The body depends on cholesterol for a variety of reasons. It helps maintaining both the structure and flexibility of cell membranes, including the cell membranes that surround nerve cells (neurons). It is a precursor to various substances, such as steroid hormones, vitamin D, and bile acids. Also, by supporting cell membranes and by interacting with molecules in the membrane surrounding the cell nucleus, cholesterol plays key roles in development of the fetus. You cannot live without cholesterol, nor can you carry a healthy pregnancy without this chemical compound. At the same time, however, cholesterol is involved in a process that damages the inner linings of arteries, including major arteries that supply the heart and brain. The process involves inflammation and the accumulation of plaques that can obstruct the flow of blood. This happens in connection with a type of particle that transports cholesterol through the bloodstream to cells that need cholesterol, a particle called low density lipoprotein (LDL). LDL differs from high density lipoprotein (HDL), whose job is to transport cholesterol to the liver and which used to be called “good cholesterol”, but now it is considered to be more of a neutral bystander. What has not changed, however, is that LDL cholesterol is still considered to be bad, if the concentration of LDL particles is high in the blood. The definition of too high depends on your health status and we’ll delve into this issue a little bit later.

Before going into the numbers, let’s define hypercholesterolemia, which means high cholesterol in the blood. It is estimated 1 out of every 200-500 pregnancies occurs in women with a condition called familial hypercholesterolemia. This is a disease in which people have very high concentrations of total cholesterol and LDL cholesterol in their blood, due to a genetic defect. They also have very high concentrations of another type of particle called VLDL. However many more people, including pregnant women, suffer from high blood cholesterol, not the familial kind, but the more common kind, which results from a combination of genetic factors, lifestyle (diet, inadequate exercise), and environmental factors.

In adults who are considered to be low risk —including healthy young and middle age women who are pregnant or trying to become pregnant— LDL cholesterol concentration is considered normal and safe if it is below 130 mg/dL. The cutoff points decrease, however, for people who have heart health risk factors, such as diabetes and coronary artery disease. People with either diabetes or various heart risk factors are given a cutoff point of 100 mg/dL. This usually means that medications must be prescribed to lower their LDL, if the untreated value is above 100 mg/dL, whereas somebody with out any risk would be offered treatment, only if her LDL cholesterol untreated is above 130 mg/dL. For those with proven coronary artery disease, or those with diabetes and risk factors for coronary, the goal is to have LDL cholesterol below 70 mg/dL. Factors such as smoking, diet, and exercise and very important and lifestyle modification can be very powerful, but those in the high risk categories typically receive cholesterol-lowering medication, because it is usually very effective.

Since high cholesterol is a very common condition, it very often occurs together with pregnancy.

For diagnosis, your LDL, HDL, total cholesterol, and another value called triglycerides are obtained from a blood sample that is drawn from you following an overnight fast. Eating within the 12 hour prescribed fasting period can mess up the results, causing confusion and repetition of tests, and in rare cases inappropriate therapy. If your cholesterol level comes out much higher than the normal range, you might be offered genetic tests for familial hypercholesterolemia. Also, since disrupted blood lipids are very much related to diabetes type 2 and gestational diabetes (diabetes occurring specifically during pregnancy), you will be tested for blood sugar levels, and also for a value called hemoglobin A1C (HbA1c). If your HbA1c is 6.5 percent, or higher, this suggests diabetes. If HBA1c falls within the range of 5.7 to 6.4 percent, this is called pre-diabetes. It is a warning sign that usually leads to your doctor counseling you to try lifestyle changes.

Diabetes in combination with high cholesterol can be particularly damaging to blood vessels, which can lead to serious problems both in the mother and the fetus. Just as high cholesterol can damage blood vessels of the heart, brain, and other organs, it also can damage the blood vessels that supply the uterus, and the blood vessels within the uterus that supply the placenta. This can lead to loss of the pregnancy. Additionally, high cholesterol can contribute to a rise in the mother’s blood pressure, and it thought to be a risk factor for the development of a serious pregnancy complication known as preeclampsia. High levels of maternal cholesterol on a long-term basis also have been implicated as a possible cause of neural tube defects (parts of the baby’s brain or spinal cord may be left without a full covering of bone).

The first choice treatment for most cases of high cholesterol are any of several medications known as statins. These drugs can lower your blood cholesterol by amounts ranging from under 30 percent to above 50 percent, depending on which stain drug is selected. Statins are among the most commonly prescribed medicines, but they must be stopped during pregnancy and breastfeeding. Other classes of medications that are used to lower cholesterol but that must be stopped during pregnancy include cholesterol absorption inhibitors, nicotinic acid, and PCSK9 inhibitors. PCSK9 inhibitors are very expensive, but currently, a gene therapy is under development that would produce the same effect as PCSK9 inhibitors, but on a long-term basis. The person would no longer need medicine. One group of cholesterol-lowering medications that are safe for the fetus are the bile acid sequestrant medications.

As for nursing mothers, all the cholesterol lowering drugs that must be stopped during pregnancy also are discouraged during breastfeeding. However, bile acid sequestrants may be continued while breastfeeding, as they do not even get absorbed from the mother’s gastrointestinal tract into her blood.

As noted above, lifestyle modification can lower your LDL cholesterol. The lifestyle changes include a dietary component and an exercise component. You should increase your consumption of fruits, vegetables, and high-fiber grains, and replace high fat meats and dairy with low-fat meats and dairy products. Such a diet can include lean poultry, and legumes. The diet also can include foods high in “friendly fat”, such as nuts, certain vegetable oils, olive oil, and plenty of fish. As we discussed in the fish article, there is a group of fatty acids called omega-3 fatty acids that seem to protect blood vessels from the development of atherosclerosis. It recent times, it has become clear that one of these fatty acids, called eicosapentaenoic acid (EPA), is particularly effective. Research is leading to treatments derived from EPA and that excludes the other omega-3 fatty acids abundant in fish. If you have no particular health problem, however, obtaining your EPA from fish in your diet —especially salmon, which, if farmed, does not contain a lot of mercury— is an excellent idea, even though another type of omega-3 fatty acid is in the food too. As for physical activity, you should perform moderate to vigorous aerobic activity, which during pregnancy can be achieved though activities such as long walks, or swimming, but other types of exercise are also possible, within reason. You should exercise for at least 40 minutes 3-4 times per week, if possible with help from a pregnancy exercise specialist.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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