Predicting delivery date

34 weeks on Thursday, and things still look good.  I’ve passed two more BPPs, and this baby continues to move and grow.  (As does my belly/ass.)

At my appointment today, I asked my doctor if there were any predictions for due dates based on how I look/my previous baby’s birth date.  She said not really, and that “all bets are off” after 36 weeks.

I’m sure many parents anxiously awaiting the birth of a new baby ask themselves, “when is this going to happen?!?”  And, of course, there’s usually not a definitive answer (unless you’re having a scheduled C-section).

There are many criticisms of the current calculation of “due date”—most importantly that it tends to be 1-4 days too early.   (And we specifically believe my due date is 3-4 days too early because (1) we know I ovulate late generally, (2) we know when we likely, um… got pregnant…, and (3) this guy was measuring 3 days late from the very, very beginning when all fetuses should be basically the same size.)

https://expectingscience.com/2014/09/29/your-due-date-is-wrong-so-when-is-labor-really-most-likely/

But, there are always odds, and these odds take into account the fact that “due date” appears to be early/off because they rely on real-life women!  So I decided to figure out what my odds are of having a baby, and specifically base them off of events coming up in my life….

Event	Chances of delivering by that date*/**	Chances of delivering on that day*
Early April baby “sprinkle”	2.5% / 0.3%	0.3%
Mid-April doula prenatal appt.	5% / 1.9%	0.6%
Early May important meeting	32% / 23%	2.4%
May 10 “due date”	48% / 42%	3%
May 13 suspected due date	57% / 53%	3%
Mid-May friend’s wedding	76% / 70%	3%

*Run using https://datayze.com/labor-probability-calculator.php (based on studies)

**Run using https://spacefem.com/pregnant/charts/duedate1.php (based on 13661 responses, 10368 occurring spontaneously)

I’m not clear why these two predictors are a little off from one another—it might just be in the populations they use.  (Note that they are close, though, especially as the due date gets closer.)

As I’ve previously mentioned, depending on how things are going my doctors might want to pressure me into inducing at 40 weeks, although at least one has indicated if things look good they should let me go to 41 weeks.  So it’s super unlikely I’ll go much past my mid-May due date, meaning there is virtually no chance I will still be pregnant for my friend’s wedding 2 weeks later.  (That being said, if I do go a little late I probably won’t be able to make the wedding.)

Something else I’ve been wondering—will this baby likely come earlier than his brother (born at 40w1d)?  Interestingly, the answer appears to be no—second time moms and first time moms tend to deliver at roughly the same pace:

https://spacefem.com/pregnant/charts/duedate6.php

In fact, I’ve read the best predictor of when you’re going to deliver your second child is when you delivered your first child.

(Although this post suggests second or later mothers may deliver a few days earlier than first time mothers: https://expectingscience.com/2014/09/29/your-due-date-is-wrong-so-when-is-labor-really-most-likely/)

In any case, I delivered my first kiddo at 40w1d, so I’m likely delivering around the same time (maybe a few days earlier) this time around.  Which means I should be able to just make my very important meeting, which is scheduled for 6 days before my due date.  Good to know!!