Should Pregnant Women Put Down The Phone? 20 Years Of Evidence Shows Mixed But Worrying Signals

Big Studies Find Little Risk From Smartphone Use During Pregnancy. Small Ones Disagree.

Pregnancy advice comes with a long list of things to skip, from raw sushi to hot tubs. Smartphones almost never make that list, even though the average user spends three to four hours a day on one. A new review of 20 studies on cell phone use during pregnancy asks whether they belong on it.

Researchers from Columbia University, Cornell University and Johns Hopkins University gathered the human research on phone use by expecting mothers and found a split verdict. Several studies found no meaningful risk. Others tied heavier use to babies born too early, slower fetal growth, miscarriage and chemical signs of cell damage in umbilical cord blood. According to the authors, the most consistent evidence pointed to two outcomes: preterm birth and changes in how the heart of a fetus or newborn works.

Before anyone locks a phone in a drawer for nine months, the researchers raise a twist of their own. Heavy phone use, they write, “may serve as a proxy for a sedentary lifestyle rather than strictly reflect radiation exposure.” Put simply, the trouble could come from hours spent sitting still with a phone in hand, and not from the signal coming out of it. Long stretches of inactivity during pregnancy may themselves be tied to shorter pregnancies and slower fetal growth, and many of the studies had no way to tell one explanation from the other.

Cell phone use during pregnancy under the microscope

Phones send and receive calls and data using radiofrequency energy, a form of radiation far weaker than X-rays. According to the review, it lacks the energy to break chemical bonds or damage DNA in a way that could lead to mutation. Still, the World Health Organization’s cancer research agency has labeled this type of energy “possibly carcinogenic to humans,” and the sheer number of hours people now spend on their phones has raised concerns about what it might mean for a developing baby.

To find out, the team searched three large research databases (PubMed, Web of Science and Google Scholar) for studies published through early February 2026. After duplicates were removed, 982 papers remained. Two researchers screened each one independently, keeping only original studies of pregnant women that measured phone use and tracked what happened to the fetus or newborn. Twenty studies made the cut.

Most of them, 16 in all, were observational. Researchers asked mothers about their phone habits, sometimes long after the pregnancy, then compared those habits with outcomes such as birth weight or delivery date. Studies built this way can reveal a link but cannot prove that phones caused anything. Four others were small experiments that placed a phone near a pregnant woman’s belly. Three tracked the fetal heartbeat, and one examined early placental tissue from women who had chosen to end their pregnancies. Study sizes ranged from 40 women to more than 100,000 births. Many came from Turkey, with the rest spread across Asia, Europe and Egypt. None were conducted in the United States.

Early births and a faster fetal heartbeat

Three studies linked phone use to babies arriving early. Largest was a combined analysis of four birth cohorts in the Netherlands, Denmark, Spain and South Korea, covering 55,507 mothers. Women in the middle group for call frequency, roughly two to five calls a day depending on the cohort, were more likely to give birth earlier in pregnancy, and the risk of a shorter pregnancy and preterm birth climbed as call volume rose. Those researchers cautioned that other, unmeasured factors could explain the pattern. Two smaller Turkish studies of 500 and 400 women tied phone use, or owning more than one phone, to earlier delivery.

Three other studies, including a Norwegian cohort of more than 100,000 births, found no link to preterm birth. Two studies from Iran raised a different concern. In a cohort of 1,666 women, longer phone calls went along with a higher risk of miscarriage, and in a study of 600 women, those who had an early miscarriage reported longer call times and higher exposure.

Experiments on the fetal heart produced some of the most concrete results. In Egypt, 90 women between weeks 25 and 40 of pregnancy were exposed to a phone in dialing mode for 10 minutes. Afterward, fetal heart rates went up and cardiac output, the amount of blood the heart pumps, went down. Newborns exposed the same way after birth also showed faster heart rates. In India, researchers placed a phone in a box about 8 inches from the bellies of 141 women at 40 weeks. During the 10 minutes it was switched on, the baseline fetal heart rate and the number of heart rate accelerations rose, though the study reported no change in outcomes around the time of birth. A Turkish experiment with 40 women found no effect on fetal heart rate at all.

A Chinese study of 2,339 women added a longer-term question. Phone use of more than five hours a day in the three months before pregnancy and during the first trimester was linked to a higher risk of congenital heart disease in offspring. Exposure to televisions, computers, microwave ovens and induction cooktops showed the same association in that study.

Larger studies paint a calmer picture

Fetal growth followed a similar split. A French study of 1,378 women found that more than 30 minutes a day of phone calls was linked to babies being born in the smallest 10% for their stage of development. In a Japanese study of 461 mother-baby pairs, mothers who rated themselves as heavily dependent on text messaging had babies with lower birth weights. A Turkish study of 1,495 mothers linked phones that give off more radiofrequency energy to higher odds of a small baby, though time spent on the phone made no difference.

Smaller studies reported other changes as well. In Turkey, 123 infants whose mothers used a phone about two hours a day while pregnant showed poorer posture and movement quality at 3 to 5 months old. Four studies found higher levels of oxidative stress, a kind of chemical wear and tear on cells, in umbilical cord blood or placenta tissue, and one also reported DNA damage. Review authors point to that cell stress as one possible route by which phones could affect a pregnancy, though the idea remains unproven.

Larger studies did not see the same pattern. Neither the four-country cohort of 55,507 mothers nor the Norwegian study of 100,231 births found a link between phone use and birth weight or fetal growth. In the Norwegian data, women with medium or high phone use showed no rise in birth defects and a slightly lower risk of preeclampsia, a dangerous blood pressure condition in pregnancy. A Spanish study of 587 mothers found little evidence that phone use during pregnancy harmed children’s development at 14 months.

Weak evidence on cell phone use during pregnancy

Authors of the review are frank about how shaky the research is. Fifteen of the 16 observational studies were judged to carry a serious risk of bias, and the last was rated critical, the worst grade on the scale. Among the four experiments, ratings ranged from “some concerns” to high risk.

Most studies relied on mothers to remember how much they used their phones, and memory makes a poor measuring tool. Few separated calls from texting or browsing, even though calls usually produce more exposure because the phone sits against the head. Few recorded the phone model, whether women used headphones, or where they kept the device. Several measured only brief exposures adding up to less than an hour, which says little about months of everyday use. Because the studies differed so much, the team could not pool their numbers into a single statistical analysis.

Even with those gaps, the authors write that “the emerging evidence may support precautionary measures to reduce mobile phone usage during pregnancy,” particularly for women with high-risk pregnancies. Their suggestions are simple: use a speakerphone or wired headset, keep the phone away from the belly, and switch on airplane mode when it sits idle. They also acknowledge that agencies like the NIH and CDC say the benefits of phones generally outweigh the risks.

“While the accumulated evidence suggests possible adverse effects of mobile phone use during pregnancy, drawing firm conclusions remains premature given the inconsistent findings and methodological limitations across existing studies,” said Dr. Ka Kahe, professor of Epidemiology at Columbia Mailman School of Public Health and the corresponding author of the study, in a statement. “Our review effectively underscores the need for more rigorous research to guide evidence-based recommendations.”

Phones deserve a spot on the pregnancy watch list, with a question mark beside them. After more than 20 years of studies, scientists still cannot say whether radiation, too much sitting or something else entirely drives the handful of worrying signals. Until researchers measure phone use directly instead of relying on mothers’ memories, a speakerphone and a few inches of distance from the belly are low-cost steps, even if no one can yet say whether they make any difference.

Disclaimer: This article summarizes a systematic review of previously published studies. Most of those studies were observational and rated at serious or critical risk of bias, so they can show associations but cannot prove that cell phone use causes any pregnancy outcome. The information here is not medical advice. Pregnant readers with questions about phone use or other exposures should talk with their doctor, midwife or other health care provider.