In a recent study, US researchers have highlighted the potential of placental examination in identifying the causes of unexplained pregnancy losses, shedding light on pathology signs in over 90 percent of the cases they investigated.
Each year in the United States, approximately 5 million pregnancies occur, with around 20 percent resulting in miscarriages before the 20-week mark, and an additional 20,000 pregnancies are lost after this point, categorized as stillbirths.
For many individuals whose pregnancies end tragically, the lack of a clear explanation for their loss adds to the emotional burden they bear. In the US, about half of all pregnancy losses remain unexplained.
Addressing this issue, reproductive scientist Beatrix Thompson and her team from Yale University advocate for the need to determine the cause of such losses and implement preventive measures where possible. They emphasize the importance of expanding the current classification systems to reduce the number of cases categorized as unspecified.
While some pregnancy losses can be attributed to infections or placental issues that are more readily diagnosed, such as umbilical cord dysfunction or premature separation from the uterine wall, the placenta plays a vital role in pregnancy. It connects the baby’s vascular system to the mother’s via the umbilical cord, supplying oxygen, nutrients, and protective antibodies while removing waste products. Therefore, any changes in this temporary organ can lead to miscarriage or stillbirth.
Thompson, along with Harvey Kliman and Parker Holzer from Yale University, examined a database of 1,256 pregnancies lost without explanation, occurring between 6 and 43 weeks of gestation. While miscarriage is defined as pregnancy loss before 20 weeks of gestation, stillbirth pertains to pregnancy loss at or after 20 weeks.
The team scrutinized placental pathology slides from each case, revealing that nearly 92 percent of cases could be diagnosed with a specific placental pathology. This included over 85 percent of miscarriages and nearly 99 percent of stillbirths.
In unexplained miscarriages, the most common pathological feature observed was dysmorphic placentas, a marker associated with genetic abnormalities. In unexplained stillbirths, a small placenta, which can restrict the baby’s growth and development, was the predominant pathological feature.
Historically, the placenta has been overlooked due to the challenges of safely evaluating it during pregnancy. However, in 2009, Kliman and colleagues developed a safe method to measure placental volume, a test that takes just 30 seconds but remains underutilized by most physicians.
Kliman highlights the potential of this research, stating that it could have detected over 7,000 small placentas associated with stillbirths each year, flagging them as high-risk pregnancies before loss occurred. Similarly, identifying dysmorphic placentas may help identify genetic abnormalities in the nearly 1 million miscarriages that occur annually in the US.
While the study boasts a substantial sample size and covers a range of timing for losses, it has limitations. As a retrospective study, it cannot establish a direct causal relationship between placental pathology and pregnancy loss. Additionally, it was conducted at a single institution, potentially limiting its generalizability to other populations.
Nonetheless, the findings hold the promise of providing individuals with a concrete explanation for their pregnancy loss, alleviating feelings of guilt and aiding in the healing process. It also has the potential to inform decisions about future pregnancies, offering individuals more clarity and control over their reproductive health.
