Why Aren’t We Better At Predicting When A Baby Is Due?


By Anna North 

Ashley Randolph was 34 weeks and five days pregnant, and she was afraid. Her first two children, Aiden and London, had been born premature, each at exactly 34 weeks. Her pregnancies had been difficult, marred by dismissive doctors, insurance hurdles, family conflict, and a severe form of morning sickness called hyperemesis gravidarum. But now Randolph was facing a new fear: Even though a full-term pregnancy lasts 39-40 weeks, she had never been pregnant this long before. What if something was wrong with the baby?

It was October 2015, and Randolph remembers standing in her grandmother’s California backyard with her boyfriend, now her husband. “I remember crying like somebody had passed away,” she said. “Knowing that I had two kids early, to me, I was expecting that 34-week, 0-day mark.” When that day passed, anxiety took over.

“I’m thinking every possible thing is going wrong,” Randolph said. “Is she not breathing? And then I had her a little over a week later.” Randolph’s youngest child, her daughter Jamie, was her smallest, born at just 3 pounds, 10 oz. She had to spend three weeks in the NICU before she was healthy enough to go home.

Randolph’s experience — three premature babies, three stays in the NICU, trauma that she’s only now recovering from — is emblematic of a deep uncertainty at the heart of contemporary prenatal care. Despite advances in everything from prenatal genetic testing to IVF, we know shockingly little about labor itself.

We don’t know precisely what causes it. We can’t predict exactly when it will start. And though researchers have identified certain risk factors, we can’t be certain whose body will begin the process prematurely, potentially putting the future child at risk of hospitalization, illness, or death. Individual people have little to no control over when they go into labor, meaning that patients aren’t to blame when something goes wrong — and there’s not much they can do on their own to influence the process.

Part of the reason we don’t understand labor very well is that it’s complicated, a multi-part process in which the biology of both the pregnant person and the fetus plays a role. But part of the reason is that research on pregnancy is chronically overlooked and underfunded, leaving one of the most basic functions of the human body shrouded in confusion and doubt.

“It’s a mystery that doesn’t need to be a mystery,” said Joia Crear-Perry, an OB-GYN and the founder of the National Birth Equity Collaborative (NBEC).

When she treated pregnant patients, Crear-Perry made sure to warn them that the baby’s due date was no more than “our best guess,” she said. Doctors estimate it by counting 40 weeks after the first day of the pregnant person’s last menstrual period, and gain a little more accuracy by measuring embryonic or fetal development with an ultrasound, but a one- to two-week window on either side of the due date is still considered normal. “If I knew exactly when the baby would come,” Crear-Perry says she told her patients, “I wouldn’t have to work.”

Starting at 36 weeks, patients typically see a doctor weekly, in part to watch for signs of labor, which is generally defined as a cervical dilation (or opening) of 2 centimeters or more, accompanied by uterine contractions, according to Martina Badell, a professor of obstetrics and gynecology at Emory University. Doctors will check a patient’s cervix and ask them about contractions, which can feel painful or uncomfortable. But there’s no blood test or other hard-and-fast way of predicting when labor will start because, as Badell put it, “the exact trigger for the onset of labor is not known.”

Doctors and scientists believe the process is probably kick-started by some combination of “hormonal, inflammatory, and mechanical factors,” Badell said. The physical stretching of the uterus as the fetus grows may play a role, as may the balance of hormones like progesterone, oxytocin, and Pitocin in the pregnant person’s body. Some experts believe the fetus itself releases some kind of chemical signal when it reaches a certain developmental point. But it’s unlikely that any one of these changes is enough to induce labor on its own. “It clearly has to be multiple pathways working in synchrony,” Badell said.

The fact that we don’t know exactly what causes labor, or when it will happen, is a big source of stress for many pregnant people and their families. Having a child is a life-changing event, and it can be nerve-wracking not to know when it’s happening: Is the bassinet ready? What about the car seat? When should the grandparents visit? There are also real economic consequences to this uncertainty in a country that doesn’t mandate paid parental leave; plenty of people need to work right up until their due dates, and some end up going into labor at work.

In other cases, doctors need to induce labor artificially — for example, if a pregnant person has a medical problem like preeclampsia that makes pregnancy dangerous, or if the pregnancy has gone long past the due date. But because we don’t understand labor very well, we’re not always good at making it happen. Doctors can induce labor using medications or procedures like rupturing the amniotic sac, but the techniques don’t always work. Sometimes labor doesn’t start at all, or is “dysfunctional,” meaning it won’t result in an actual delivery. In these cases, patients need a C-section, which comes with greater risks for the birthing person and often a longer recovery time. “If we understood the natural labor progress more completely, we could target our therapies for labor induction better,” Badell said.

Many pregnant people who reach the 39- or 40-week full-term mark start looking for natural ways to induce labor. They might want to avoid a medical induction or C-section, or they may just want pregnancy to be over. As Melinda Wenner Moyer wrote, “I was huge and everything ached, and I was desperate to meet my babies.” TikTok and Instagram are full of advice for starting labor on your own, but most of the tips — from drinking pineapple juice to eating spicy food — have not been proven to work. A few tricks, including nipple stimulation and drinking castor oil, have some evidence behind them, but more research is needed (also, many people find castor oil disgusting).

The guesswork around labor also becomes a medical problem when the process starts too early. Labor that begins before 37 weeks, as in Randolph’s case, is considered preterm, and when it leads to preterm birth, it’s associated with a host of potential complications. Babies born prematurely — about 10 percent of those born in the US every year — are more likely than full-term infants to have health problems at birth like jaundice, difficulty breathing, and brain hemorrhages, and ongoing issues like learning disabilities and vision problems. “Prematurity is a huge contributor to neonatal and pediatric morbidity and mortality,” said Christian Pettker, a professor of obstetrics, gynecology, and reproductive sciences at the Yale School of Medicine. “It’s a major risk to the newborn and to the child.”

A premature birth can also be traumatic for birthing people and their families. Randolph says that even seven years after the birth of her youngest daughter, she can’t forget the feeding tube doctors in the NICU had to thread up her baby’s nose and down her throat. “To see her yank it out because it was bothering her, and then I would see them put it back in there,” Randolph said, “that is something that will stay with me probably forever.”

“You almost feel less of a parent,” she said, “because you can’t protect them the way that you should.” Research has shown that mothers whose babies are admitted to the NICU are at elevated risk of postpartum depression.

Many parents of preterm babies feel guilt, believing they somehow caused their child to be born early, but preterm labor is poorly understood and largely out of the pregnant person’s control. Researchers have identified some risk factors, including infection, abdominal trauma, and having a shortened cervix. One of the biggest predictors of giving birth prematurely is already having had a premature baby — not exactly helpful information for first-time parents. Black women are also about 1.6 times as likely as white women to give birth prematurely, a disparity many attribute to the same systemic racism and medical bias that lead to disproportionate maternal mortality among Black birthing people. “There’s nothing different about my vagina, my cervix, or anything else,” said Crear-Perry, the NBEC founder, but “how I’m racialized does impact my health.”

Understanding what causes preterm labor — including the pathways by which racism affects pregnancy and birth — could save thousands of lives every year. Researchers still struggle with this crucial question partly because it’s difficult to study: Experimenting on pregnant people raises a host of ethical and logistical questions. Another big reason, though, is money.

“We’ve massively underinvested in pregnancy research in this country,” Pettker, the Yale professor, said. Pregnant people are “a massively vulnerable population that does not show up on the radar screen of enough people like legislators and pharmaceutical companies, and private scientific organizations.”

The underinvestment in pregnancy research is part of a larger pattern of underfunding research into conditions and diseases that primarily or disproportionately affect women, including migraines, endometriosis, and menopause. The National Cancer Institute within the National Institutes of Health has a $7 billion budget; the budget for the Office for Research on Women’s Health is $76 million.

What’s more, a lot of pregnancy research has been “hyperfocused on the woman or the birthing person and their choices,” like diet and exercise, Crear-Perry said. “We blame individuals instead of the structures and systems.” That means not enough researchers looking at how structural harms like racism contribute to pregnancy complications.

“The choice not to study preterm birth,” Crear-Perry said, “is a gendered and racist choice.”

Though individuals may not be able to do much to influence when they go into labor, there are steps policymakers can take to improve understanding of the process and help families and babies. It starts with funding the science that has been neglected for too long, Crear-Perry said. That includes increasing the budget for the Office for Research on Women’s Health, as well as incentivizing states to collect better data on maternal and infant health. The Black Maternal Health Momnibus, a legislative package introduced by Reps. Lauren Underwood (D-IL) and Alma Adams (D-NC), includes measures to invest in housing, transportation, nutrition, and other social factors that can influence maternal health, as well as to improve data collection.

The Republican-controlled House makes the prospect of passing the Momnibus a dim one for now. But in a broader sense, the pandemic has thrust the country into a time of transition where it may be ripe for finally facing its maternal health crisis head-on, Crear-Perry believes. “We went through a lot these past two years and we have an opportunity to say, ‘Okay, let’s study what causes labor,’” she said. “We could do it today.”

In the meantime, Randolph has a wishlist of simple changes that would help parents of premature babies today, from information about the NICU before delivery, to connection with a support group afterward, to resources to take home with their babies. After her first daughter’s birth, she started an organization called GLO Preemies, which supports Black NICU families from pregnancy until the child turns 18. The group provides workshops, webinars, and care boxes that include items like diapers, baby clothes, and nipple balm.

She also calls on Congress, insurance companies, hospital executives, and doctors to prioritize the health of pregnant people and babies. “We just have to do better as a whole,” she said. “I think that counts for everyone.”


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