Osteoporosis During Pregnancy and Breastfeeding

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Osteoporosis is a condition in which the density of mineral content in bones is below normal. This means that the strength of bones is below normal, which puts you at elevated risk of fractures, especially on the high weight-bearing parts of your skeleton, such as the hips and spine. Osteoporosis typically is an issue for post-menopausal women, because of decreasing amounts of the hormone estrogen in the body. When estrogen levels drop, this enables bone-eating cells, called osteoclasts, to live longer, so bone mineral is destroyed and an accelerated rate. A very rare type of osteoporosis called pregnancy lactation osteoporosis (PLO) has been reported to occur during the third trimester and after delivery in a total approximately 100 women, but the regular type of osteoporosis —the type that affects post-menopausal women— also can occur in younger women, including in those who are pregnant. This relates to the fact that pregnancy entails changes to the musculoskeletal system, including a high demand for calcium from your body to support the baby’s developing bones. This creates a substantial need for you to consume vitamin D and calcium.

Osteoporosis affects hundreds of millions of women and is thought to be under-diagnosed. Numerous factors can elevate your risk of developing osteoporosis. Because strong muscles lead to strong bone, women who are lightweight or who avoid weight-bearing exercise are at particularly high risk. Because weightlessness unloads the forces that usually act on our muscles and bones, astronauts have demonstrated a loss of 1-2 percent of bone density for every month that they spend in weightlessness. This issue translates well for people on Earth who are in bed rest for long periods of time. What this means for you is that exercise can greatly change your risk of developing either osteoporosis, or osteopenia —a kind of pre-osteoporosis, characterized by decreased bone density, not to the point that we can all it osteoporosis. Women of Caucasian and Asian background have an elevated risk of osteoporosis compared with women of African descent, due both to differences in estrogen levels and weight. Corticosteroid medication (such as for asthma or for autoimmune disease) and epilepsy medication, particularly a drug called phenytoin, also promote loss of bone density, as does smoking. Probably, smoking by itself is not enough to be a primary cause of osteoporosis, but it can help push you into osteoporosis, if your bones are already losing bone mineral density, as a result of decreasing levels of estrogen, inadequate exercise, inadequate vitamin D, or if a gastrointestinal condition to keeps you from absorbing various nutrients.

Osteoporosis can cause you to suffer a bone fracture from small falls or other actions that otherwise would not be enough to cause a fracture. Such fractures can occur in particularly critical locations, such as the hip and spine. If this happens during pregnancy, you may be better off delivering with a caesarian section to avoid strain on the pelvic bones. As noted earlier, osteoporosis during pregnancy is extremely rare. However, osteoporosis during pregnancy will not have any direct impact on the baby. Your body will simply continue drawing a supply of calcium and phosphate from your own bones to support the needs of the fetal skeleton. If you attempt to nurse after you deliver, this process would accelerate.

Your doctor can diagnosis osteoporosis with a special type of X-ray imaging called dual X-ray absorptiometry (DEXA) scanning. There is a tendency among health practitioners to avoid DEXA in pregnant women, due to a fear of low dose radiation that is common in our society. Sometimes this fear of radiation is called radiophobia, though in the case of doctors it mostly involves a fear of potential lawsuits. However, while the dose of ionizing radiation from a DEXA varies widely depending on how much of the body is scanned, it is always measured in microsieverts (µSv), meaning that is exquisitely low. From the natural background radiation on Earth, the average pregnant women in the United States receives hundreds of times such a dose when living at sea level, or hundreds to thousands of times such a dose for those in high altitude cities, such as Denver or Salt Lake City, with no harmful effects to the fetus; that’s without any medical procedures and without flying on any aircraft. Consequently, if you have suffered from unexplained fractures, or have a family history of osteoporosis beginning at a young age, it is reasonable to ask your doctor for a DEXA scan, even when you are pregnant.

In DEXA, the result, known as a T score, is given as a negative number, such that the more negative the score, the lower the bone density. A DEXA score between zero and -1.0 is considered normal bone density. T-score of -1.0 to -2.5 indicated osteopenia, meaning low bone density, while T-score of -2.5 or lower means osteoporosis. In addition to DEXA scanning, doctors will also get a blood sample for a comprehensive metabolic panel (CMP, also called a CHEM-14), and a complete blood count (CBC), plus levels of parathyroid hormone (PTH), looking for potential underlying causes of bone mineral loss.

Osteoporosis and osteopenia are treated with a group of medications called bisphosphonates (BPs). When taken orally, these drugs can cause inflammation of the esophagus and other problems that potentially can lead ultimately to esophageal cancer. Consequently, if you take BPs, you need to follow the pill with a full glass of water and remain standing for at least 30 minutes. On the other hand, if you choose to have the medication injected, you can avoid the esophageal risks. BPs cross the placenta and there is some concern about their safety in pregnancy, but the concerns are based only on laboratory animal studies using doses much higher than what you would receive for osteoporosis. Consequently, the question on whether to take these drugs during pregnancy is a matter of weight benefits against risks. Very little is known about BPs in nursing mothers, because very few women are taking these drugs prior to menopause. If you have one of the rare cases of PLO, however, it may not be wise to nurse, since production of breast milk draws an enormous amount of calcium, which will exacerbate your condition. In such cases, you will likely be better off choosing one of the excellent infant formulas on the market. Additionally, you should be taking vitamin D and calcium supplements during pregnancy and while nursing.

Regular exercise that includes weight bearing, high impact activity is an excellent way to promote bone density. It is also important to get adequate amounts of vitamin D and calcium. It is possible to get enough calcium from your diet, and sunlight does provide you with vitamin D, but during pregnancy it is virtually impossible to get enough vitamin D without vitamin D supplements.

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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