My Due Date Changed Three Times: What Nobody Tells You

When my OB moved my due date from December 15th to December 22nd and then back to December 18th, I learned how fuzzy this whole concept really is.

My first pregnancy, I was so excited to get that little due date card from my OB. December 15th. I circled it on the calendar. I told everyone. I planned my maternity leave around it.

Then at my 12-week ultrasound, the tech measured the baby and said, "Hmm, you're measuring a bit small." My OB came in and said, "We're moving your due date to December 22nd."

I was devastated. A whole week later? I had already told my family Christmas plans. I had already mentally prepared for a mid-December baby.

Then at my 20-week anatomy scan, they measured again. "Actually," the OB said, "let's split the difference. December 18th."

Three due dates. For the same baby. And you know what? She came on December 20th. None of the dates were right.

Why Due Dates Change

Here's what I learned as a midwife that I wish someone had told me as a patient:

• Early ultrasounds are most accurate. The 8-13 week dating scan is the gold standard. After that, babies grow at different rates.
• LMP assumes a 28-day cycle. If your cycle is 30, 32, or 35 days, your "standard" due date is already off by days or even a week.
• IVF dates are the most precise. Because we know exactly when fertilization happened, there's no guessing.
• Only 4-5% of babies arrive on their due date. The "normal" window is 37-42 weeks. That's a 5-week range.

What I Tell My Patients Now

I never give my patients a single date anymore. I give them a window. "You're due around the third week of December." I tell them to plan for 38-42 weeks. I tell them the due date is a guess, not a deadline.

And I tell them what I wish someone had told me: the baby will come when the baby is ready. All the planning in the world won't change that.

— Sophie Miller

Sophie Miller is a Certified Nurse-Midwife in Portland, Oregon. This article reflects her personal experience and clinical observations. For medical advice, consult your healthcare provider.