When your OB first tells you your due date, it feels like such a sacred number. You roll it over and over in your mind, and you proudly recite it when inquisitive friends, family members, and coworkers ask you when you're due. Yet, in reality, your baby could just as easily be born two weeks before or after that date. My daughter was born in a different month than her due date predicted. If you suspect your date might be wrong, here are some signs you due date is off, so you and your OB can make a game plan.
It may seem weird that a date assigned by a medical professional could be little more than a "guesstimate" but that's kind of what it is. In fact, only 5 percent of babies are born on their actual due date, according to Parents.
What's more, the method used to calculate due dates hasn't changed since the beginning of the 19th century, according to New York Magazine. You would think that with all the technological advances in fertility and fetal medicine, that due dates might have also gotten a boost, but nope, doctors still use something called the Naegele rule, which is when, "you take the first day of a woman’s last menstrual period, add a year, subtract three months, and add seven days," explained the New York Magazine article.
With calculations like that, you can see why due dates aren't exactly an exact science. But if you're looking for more clarity, here are five indicators that you might deliver earlier or later than your original due date suggests.
1. Ultrasound Date Is Greater Than 7 Days Apart From Due Date
Pregnancies can either be confirmed with a doppler heartbeat monitor or a first trimester ultrasound, according to What to Expect.
If you have an ultrasound, and the ultrasound-determined due date is more than seven days apart from your menstrual-cycle determined due date, your OB will defer to the ultrasound date, according to the same What to Expect article.
In fact, first trimester ultrasounds (up to and including 13 6/7 weeks of gestation) are the most accurate method to determine gestational age, according to the American College of Obstetricians and Gynecologists (ACOG),
2. Your Fundal Height Is Off
When you go in for check-ups, your OB might measure something called "fundal height", which is the distance from your pubic bone to the top of your uterus, according to The Bump. Your fundal height typically syncs up with how far along you are, so for example, if you're 32 weeks pregnant, your fundal height will be close to 32 centimeters.
However, if your fundal height is more than two centimeters off in either direction, your OB might order an ultrasound to determine if your due date is off, The Bump explained.
3. Your Demographics
Due dates are based on 40 weeks of gestation but depending on your age and other demographic factors, 40 weeks might not even be the right baseline. "Research has shown, for example, that women under the age of 19 or over the age of 34, black women, and those who have already given birth to at least one child are likely to have shorter pregnancies," explained New York Magazine.
While more than half of pregnancies do go to 39-40 weeks, nearly a quarter of pregnancies are considered "early term", or 37-38 weeks, reported the same New York Magazine article, citing data from the National Vitals Statistics Report.
4. Your (Or Your Mother's) Birthing History
They say that history repeats itself, but did you know that applies to childbirth too?
"Patients tend to repeat what they did in a previous pregnancy," explained Iffath Hoskins, M.D., executive director of the Women's Service at the Memorial Health University Medical Center, in an interview with Parents.
If this is your first pregnancy, you might still be able to learn something from history, you just need to go back to your mom's labor tales. "If your mother delivered one week past her due date, you are more apt to deliver one week past your due date as well," explained Fredric D. Frigoletto, Jr., M.D., chief of obstetrics at Massachusetts General Hospital, to Parents.
5. You Drop Early
If you suspect that your due date is off, pay close attention to when your belly "drops." In my case, my belly dropped early, and sure enough, my daughter arrived two weeks ahead of her due date.
Dropping, or "lightening" as it's sometimes called, happens when "the baby’s head literally "drops" lower into your pelvis, becoming engaged within your pubic bones. This starts baby’s descent down and out into the world," explained Healthline.
Some pregnant women drop a few weeks before giving birth, and others drop a few hours before labor starts, but that belly "drop" is one major sign that labor is approaching, according to the same Healthline article.