Non-Oncology Applications: 12 of 14

Pregnancy Complications

Some pregnancies develop problems that can put the mother, the baby, or both at risk. One of the most important is preeclampsia, where the mother's blood pressure rises dangerously and her organs can begin to suffer. Other complications include preterm birth and poor growth of the baby.

This is different from prenatal testing, which uses blood to look at the developing baby's chromosomes. Here the main question is how the pregnancy itself is progressing, especially how well the placenta is working. The placenta is the organ that connects the mother's blood supply with the developing baby.

Because the placenta is in constant contact with the mother's circulation, it releases a steady stream of material into her blood, including DNA, RNA, proteins, and packages of material released by its cells. When the placenta is not developing or functioning normally, as happens in preeclampsia and many cases of poor fetal growth, those signals can change. Some of the changes are measurable weeks before symptoms appear.

Most of the interest is in prediction. Once preeclampsia is established, it is usually not difficult to recognize from blood pressure and urine testing. By then, though, the condition is already present and the choices may be limited. Delivery is the only definitive treatment. Identifying high-risk pregnancies earlier can lead to closer monitoring and, in some cases, preventive treatment that works best when started early. With preterm birth, advance warning can affect where someone gives birth and whether medication is given in time to help mature the baby's lungs.

The timing creates a problem. A prediction has to come early enough to change care, but the biological signal often becomes clearest as the complication gets closer. The most accurate measurement may arrive after the point when it would have been most useful. Definitions also matter. Some pregnancy complications are defined by cutoffs on clinical measurements, and those cutoffs have changed over time, so studies from different periods may not be counting cases in exactly the same way.