Q&A: Pregnancy and lactation-associated osteoporosis rare, but serious
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Pregnancy and lactation-associated osteoporosis is an uncommon diagnosis, but one that has substantial impact on fracture risk for mothers. The condition also may increase osteoporosis risk for their children later in life, an expert said.
Healio spoke with Braden G. Barnett, MD, clinical assistant professor of medicine in the division of endocrinology and diabetes at the University of Southern California (USC) Keck School of Medicine, Los Angeles, to learn more about the prevention and treatment of osteoporosis for pregnant women along with effect of the condition on pregnancy.
Barnett will speak on this topic as part of the USC Jorge H. Mestman Endocrine in Pregnancy and Women’s Health Symposium taking place virtually Feb. 18. Register for the symposium at keckusc.cloud-cme.com/course/courseoverview?P=5&EID=5614.
Healio: We tend to think of osteoporosis as a disease of older women. How might osteoporosis affect younger women?
Barnett: Osteoporosis is a term that is meant to help identify people at higher risk for fracture. It’s less of a distinct condition and more of just trying to risk stratify. Younger women usually don’t fall into this high-risk category unless there’s some kind of risk-enhancing factor. In this case, pregnancy and, even more, lactation can lead to a high-risk state for certain women. That’s where we get this term “pregnancy and lactation-associated osteoporosis,” which is often abbreviated PLO.
Healio: What do we know about osteoporosis during pregnancy in terms of why it arises and longer-term disease trajectory? Can we analogize to gestational diabetes and risk for type 2 diabetes later in life, or is this different?
Barnett: Probably the biggest factor that leads to a higher risk state for osteoporosis is certain genetic factors that might predispose someone to having fractures later. A lot of these are probably things that we don’t know how to test for or how to quantify. We just know that if a person’s family history shows they might be predisposed, then that person might have a higher risk.
That does seem to be true about PLO, in that there are certain genes that we know to test for as “genetic causes” of osteoporosis. It seems like there’s a higher propensity of women who end up with PLO who have one of these known genetic mutations.
Use of certain medications can certainly predispose to bone loss as well. That’s not as much of an issue with pregnant women, since most of them are usually young and not taking many or any medications. We know that alcohol and tobacco use increase fracture risk to some extent, but probably the biggest factor that can predispose to the development of PLO is genetic risk factors.
Is this analogous to gestational diabetes and type 2 diabetes? In a sense, it is similar in that women who develop PLO are almost certainly going to be at an increased risk for developing osteoporosis that we would sort of expect to see in the postmenopausal state. So, osteoporosis that is typically diagnosed after the age of 50 years. A woman with PLO probably is at a higher risk of that happening. PLO is much less common than gestational diabetes, that’s why we screen for gestational diabetes, as every pregnant woman gets screened for gestational diabetes, whereas we don’t screen for PLO routinely because it’s just so rare.
Healio: Does osteoporosis during pregnancy affect children or only the mother and why?
Barnett: During the lactation period, the bones are even more affected, but during both pregnancy and lactation, only the mother is affected. The reason why it’s during lactation especially, is because the mother’s body shifts to sending out a lot of calcium to the baby through the breast milk. That net calcium loss during lactation is really the main source of the problem in PLO. During that time, the baby’s bones are getting bigger and getting stronger, but if a woman does have PLO, her bones are presumably losing calcium while the baby’s bones are gaining calcium. We do know that that baby, as they grow up, probably will have a higher risk for developing osteoporosis later because clearly their mother had a genetic predisposition to osteoporosis, and so they likely will as well.
Healio: Younger women are not routinely screened for osteoporosis. How is osteoporosis during pregnancy identified and addressed?
Barnett: Fortunately, it is very uncommon and very rare when you consider how many pregnancies there are and how many women are being diagnosed with PLO. Because of this — and also because some of the screening tools we would use to look for osteoporosis in nonpregnant women we can’t use with pregnant women — we end up using an outcome-based diagnosis. This means we wait until someone presents with a fracture to then diagnose them with PLO. It’s not ideal that we basically are only able to enact secondary prevention. We’re only able to try to institute measures to prevent further fractures after someone has already suffered one. We don’t have tools available right now for us to be able to do a good job of primary prevention.
The test that is most common to screen for and diagnose osteoporosis is the DXA test, but you can’t do a DXA on a pregnant woman because you’d be exposing the fetus to harmful radiation in the form of an X-ray. You can do DXAs on women who are lactating after they’ve delivered, but while DXA can be helpful in that it can give you some idea of risk, it doesn’t correlate perfectly with fracture outcomes. So, we’re still limited.
Right now, there is no recommendation in terms of screening for PLO. We basically just wait and see if women show up with fractures, which thankfully is rare. Otherwise, we try to enact preventive measures through having women take enough calcium and vitamin D along with prenatal vitamins. This probably helps mitigate to some extent, but it’s hard to predict which women are going to show up with PLO and which aren’t. So, we must be very careful clinically and monitor people closely.
Studies have looked at using ultrasound on various parts of the body, and I think that’s promising to some extent. You can use ultrasound to try to quantify bone density, you can use MRI to look for fractures, and maybe you can get information from an MRI about the quality of the bones to some extent. But you’re still limited because you don’t know who is going to fracture until they fracture.
This is a problem in diagnosing run-of-the-mill osteoporosis outside of pregnancy and lactation as well. The tools that we have are imperfect, to say the least. So, there are ongoing studies on how to better diagnose osteoporosis, both in pregnant women and nonpregnant women, but we still have a lot of work to do in terms of refining our tools.
Healio: How is this treated and what is the importance of treatment?
Barnett: The outcome we care about is broken bones, and this goes for osteoporosis in pregnant women, lactating women and nonpregnant, nonlactating women.
If a woman is diagnosed with PLO during the pregnancy, it’s a less common time to see fractures than during lactation. Lactation is a major factor in terms of decreasing bone density and increasing fracture risk. If a woman was diagnosed with PLO, we would recommend against her doing lactation with any future pregnancies.
There’s some evidence that using estrogen, especially a transdermal estrogen, during lactation might be helpful in terms of stabilizing bone density to some extent. This is safe, although it doesn’t mitigate the factors completely. The loss of calcium during lactation is a major problem. It is important to make sure that women are getting enough calcium and vitamin D supplementation, which most prenatal vitamins have, and have more than adequate amounts of screening for any other potential secondary causes that might be reversible, do blood testing to look for deficiencies of other minerals like magnesium or phosphorus and look at any other possible treatable source, and use other osteoporosis medications like bisphosphonates or parathyroid hormone analog medications.
My treatment plan for a patient with PLO will be generally to recommend against breastfeeding lactation. If they insist on lactation, I would perhaps consider putting them on estradiol during the lactation phase, and then I would wait until they’re either not pregnant or not breastfeeding, and I would treat them with some kind of pharmacotherapy for osteoporosis, either a bisphosphonate or an anabolic agent.
Healio: Do you have any practice pearls for other physicians?
Barnett: In researching the way women present during pregnancy, you must have a somewhat higher index of suspicion because during pregnancy, women are going to be uncomfortable, they’re going to have various pains and aches, and it can be hard to distinguish what’s normal vs. something that is pathologic that needs further investigation.
During lactation you could send women for X-rays if a woman is presenting with signs and symptoms that would be consistent with a fracture, either in the spine or potentially in the hip. We should not be doing DXA testing routinely on women who we don’t think are at extremely high risk for fracture. Either someone who has already had a fracture or maybe if their mother or their sister had pregnancy or lactation associated osteoporosis, then you might feel justified sending those patients for a preventive a screening. Finding ways to identify women before they have their first fracture is what we’re looking to do in the future, but we might need to develop better tools with better prediction without radiation involved.
For more information:
Braden G. Barnett, MD, can be reached at braden.barnett@med.usc.edu.
He will speak on this topic as part of the USC Jorge H. Mestman Endocrine in Pregnancy and Women’s Health Symposium taking place virtually Feb. 18.
Register at: keckusc.cloud-cme.com/course/courseoverview?P=5&EID=5614
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