Unless you’re one of the chosen few who give birth on the day your baby is “supposed to” arrive (a mere five percent of pregnant women), a due date can feel like a bit of a joke. For some moms—especially first-time ones—that date may extend by a couple of weeks, which doesn’t help when you’re getting barraged by inquiring minds wanting to know if you’re in labor (FYI: It’s fair to assume that no news means no news). 

Like it or not, it’s a waiting game—or at least it was. A new analysis from Thomas Jefferson University in Philadelphia, Pennsylvania is suggesting there may be a more accurate way of predicting when a baby will arrive beyond the standard method of counting 280 days since the first day of a woman’s last menstrual cycle.


According to CNN, the secret may lie in measuring the cervix’s length via ultrasound between 37 and 39 weeks. The study, which analyzed 735 single-child pregnancies, found that when the cervix was 10 millimeters or less, there was an 85 percent chance the baby would arrive within seven days. When the cervix was less than 30 millimeters, the likelihood of delivering within the week dropped to 50 percent.

Another benefit of a more accurate due date is that it could provide military families or partners who travel for work a valid excuse to stay put when the time appears near.“Women always ask for a better sense of their delivery date in order to help them prepare for work leave, or to make contingency plans for sibling-care during labor,” Dr. Vincenzo Berghella, director of maternal fetal medicine at Thomas Jefferson University Hospital and lead author of the study, said in a press release. “These are plans which help reduce a woman’s anxiety about the onset of labor. But having a better sense can also help obstetricians provide information that could help improve or even save a mother or baby’s life.”

But other medical professionals have their doubts. As Fahimeh Sasan, assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai, told Time, “Measuring a cervical length with transvaginal ultrasound between 37-39 weeks can be quite difficult because the cervix is not fully [or] optimally visible in all pregnancies via ultrasound at this gestation, hence making measurement not very reliable nor reproducible.”

Plus, there’s the debate over how many ultrasounds are considered too many. According to the American College of Obstetricians and Gynecologists, only one or two ultrasounds are recommended for low-risk, complication-free pregnancies and should “be used only when clinically indicated, for the shortest amount of time and with the lowest level of acoustic energy compatible with an accurate diagnosis.” As it is, women are getting an average of 5.2 ultrasounds per pregnancy—a 92 percent increase since 2004, reported The Wall Street Journal. Though research has yet to confirm any negative, long-term side effects of an ultrasound on humans, some animal studies suggest “ill effects” on embryos of mice and chickens. The Wall Street Journal also points out that increased use of prenatal ultrasound scanning may account for the rising rate of potentially unnecessary caesarean deliveries due to overestimating the fetal size.

If you’re pregnant, would you be willing to try out this new due date predictor?



  1. CNN: A Better Way to Predict Baby’s Due Date?
  2. Medical Daily: A More Precise Due Date Could Benefit Both Working Mother and Baby
  3. TIME: There May Be a Better Way to Predict Due Dates
  4. The Wall Street Journal: Pregnant Women Get More Ultrasounds, Without a Medical Need