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Diagnosis of preterm labor: pregnancy as a technical challenge

Why are babies born prematurely? Researchers still don’t really know.

Authors

  • Melissa Skala

    Professor of Biomedical Engineering, University of Wisconsin-Madison

  • Kristin Myers

    Professor of Mechanical Engineering, Columbia University

  • Michelle L. Oyen

    Associate Professor of Biomedical Engineering, Arts and Sciences at Washington University in St. Louis

Midwives are very good at guiding the birth process. But when it comes to predicting whether a baby will be born on time, science is still catching up. Research into the causes of premature birth lags decades behind that of other conditions such as cancer. That means nurses, doctors, midwives and doulas don’t have the resources they need to do the best job possible when babies are born before the 37th week of pregnancy.

One of the few known risk factors for preterm birth is whether a pregnant person has previously delivered a premature baby. Others include being pregnant with twins, triplets or more, and certain medical conditions such as urinary tract infections, high blood pressure or diabetes. However, knowing these risk factors does not always point to the cause of premature birth.

Progress has been slow in part because much of the research on preterm birth to date has approached pregnancy from the perspective of reproductive biology. That includes the enormous physiological changes in the reproductive, cardiovascular and endocrine systems of the pregnant person, and the influence of hormones and genetics on both the parent and the fetus.

Yet pregnancy is also a technical challenge, because physical forces are involved. Doctors are dealing with a baby weighing an average of 3.2 kg in about 1 liter of amniotic fluid held in place with a membrane less than 1 millimeter thick – all in a uterus that was initially the size of a fist. This involves forces, pressure and mechanical stress, all of which can contribute to maternal, fetal and placental conditions that can cause premature birth.

In an article published over 150 years ago, a physician recognized that birth is a mechanical event. But he used 19th-century technology to measure the pressure per area on the membranes that support pregnancy. Only now do researchers have the mechanical, electrical and computational engineering expertise to tackle the challenges of preterm birth.

But research into preterm birth is still so early that scientists must first develop the tools to study it before they can diagnose and treat it. Our team of researchers is working to do just that.

Many complications can cause premature birth

It is difficult to determine who is at risk for preterm labor because there is no single cause. Preterm birth can be caused by multiple factors involving the pregnant person, the fetus, the placenta, or the fetal membranes attached to the placenta that connect the fetus and parent.

Worldwide, 1 in 10 live births is premature, or born before 37 weeks’ gestation. Of these preterm births, approximately 30% to 40% are caused by premature rupture of the fetal membranes, and another 1% to 9% are caused by premature dilation of the cervix.

With current technology, premature births can rarely be prevented. Current screening tools to measure the risk of preterm birth are quite primitive. Doctors use ultrasound to check the baby’s size and position, and they touch the cervix to feel if it is softening, a normal process before delivery but problematic if it happens too quickly.

If the baby is not growing, perhaps because of insufficient blood supply to the placenta, doctors perform premature cesarean sections to prevent stillbirth. Preventive cesarean sections are also sometimes used to prevent or treat preeclampsia or dangerously high blood pressure during pregnancy.

In either case, patients and physicians weigh the benefit of an early cesarean section for the fetus and parent against the risks associated with preterm birth, including lifelong respiratory, vision, cardiovascular, or other health problems for the child.

The wide variety of factors that play a role in preterm birth makes early diagnosis a challenge. But a better core understanding of the biomechanical forces at work during pregnancy could give researchers new places to look for diagnostic clues.

Tackling the challenge from multiple angles

Pregnancy is essentially a physical process, from the stretching of the uterus to accommodate the baby, to the dilation of the cervix when contractions begin and it’s time for the parent to push. And if something goes wrong mechanically, it can lead to tragic consequences.

Maternal risk factors for premature birth include uterine rupture or preeclampsia. The placenta can also detach from the uterine wall, causing the parent to bleed to death. Carrying twins is associated with extra amniotic fluid and blood volume, which puts extra strain on the placenta, which can cause premature birth.

Our team of biomechanical and biomedical engineers work from different angles to understand the underlying causes of preterm birth, all with the aim of diagnosis and intervention.

One of us, Kristin Myers, studies the biology of tissue remodeling to quantify the biomechanics of pregnancy. Her lab creates computer models to measure how the uterus, cervix and fetal membranes work to support the mechanical stress that pregnancy brings. She and her team use ultrasound to watch how the uterus grows and stretches and how much mechanical stress is on the cervix to predict whether it will fail too quickly. Using the uterus as a gauge for the mechanical environment of pregnancy can help identify problems before they arise.

Another of us, Michelle Oyen, studies the physics and materials science of soft tissues, focusing on the mechanical properties of fetal membranes and nutrient transport in the placenta. Her lab, along with Myers’ team, is applying big data and machine learning to anonymized medical records to create digital twins — or computational models of a given patient’s health data — that can help predict how a pregnancy will unfold. This can help doctors treat or prevent pregnancy complications.

Finally, Melissa Skala uses a non-invasive technique called optical coherence tomography. This imaging method produces 3D images of tissues that cannot be captured with ultrasound or MRI, such as extremely thin fetal membranes. Her lab used this technique to study how fetal membranes rupture under different pressures, providing a baseline of information that can be used to build better digital models of fetal membrane stress. Improved imaging of the fetal membranes and cervix can alert doctors when these structures are at risk of failure.

Better imaging and better models

The holy grail of premature birth prevention is early diagnosis. An early warning checklist for the risk of preterm birth can help protect the health of both the baby and the mother.

This checklist could look like your doctor ordering an imaging scan as soon as you find out you’re pregnant to understand the size of your uterus and cervix. They may then take a smear of vaginal fluid to analyze the biological changes in your cervix.

Better modeling techniques could assess how your pregnancy will progress, and more accurate imaging tools could measure changes over time. With a better prediction of when labor will begin, doctors and patients can make a more informed decision about whether a cesarean section is necessary.

Close-up of a person holding a premature baby over a scale
Knowing when someone is at risk for preterm labor can help prevent this. Christian Bowen/Unsplash, CC BY-ND

An accurate early warning checklist for preterm birth is still years away. But researchers in reproductive biology, epidemiology, bioinformatics and engineering are working hard to better understand how babies are born and the many complications that can arise, including premature birth.

We believe that engineering – creative problem solving using technology – is a crucial addition to the multidisciplinary approach needed to tackle the complexities of preterm birth.

The conversation

Melissa Skala receives funding from the National Institutes of Health and the National Science Foundation.

Kristin Myers receives funding from the National Institutes of Health, the National Science Foundation, and The Iris Fund.

Michelle L. Oyen receives funding from Wellcome Leap as part of the In Utero Program, and from the National Institutes of Health.

Michelle is an Associate Fellow of Homerton College, Cambridge.

/ Thanks to the conversation. This material from the original organization/author(s) may be contemporary in nature and has been edited for clarity, style and length. Mirage.News takes no institutional positions or parties, and all views, opinions and conclusions expressed herein are solely those of the author(s).

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