Anti-Natal Care: A Gross Recalculation

[This is the second in a short series of posts I'm calling "Anti-Natal Care", telling the story of my interactions with St. Luke's Hospital and Medical Center just before and shortly after the birth of Calvin.]

and now for something completely different

When last we left me, I was annoyed and worried about being 1 week overdue and possibly predisposed to a gestation length of 43 weeks. But I was going ahead with the hospital schedule of having two fetal non-stress-tests between 41 and 42 weeks, mostly just to follow the hospital’s protocol but also to provide useful information to my homebirth midwife, Maria, if there happened to be anything wrong.

So I called the hospital. Hilarity ensued.

After leaving the message with my favorite nurse-midwife, Julie, I got a call back from her within about 2 hours. (That’s not bad.) What she had to say threw me for a loop; the first thing she did was ask me why I thought I was at 41 weeks.

I said, “September 24th is the due date we’ve been using since our first appointment at St. Luke’s. It’s based on conception date, which I’m pretty darn sure of.” I hadn’t ever calculated my own due date; I let Julie do it, and trusted the number even more when we went to Maria and she pulled the same result.

“Hmm, okay,” she said. “So, actually, I reviewed your charts and ultrasounds and ran it through a much more sophisticated algorithm, and it looks like your due date ought to be September 29th.

Me: “What!? Um. Ok…?”

Keep in mind I’m hearing this on September 30th, a solid 6 days after my given Due Date, and 7 days before They kidnap me and pump me with pitocin, unless I go into labor naturally before then.

There’s an algorithm, Julie explains, that they can use to evaluate the trajectory of the baby’s growth using the two standard ultrasounds (9 weeks and 20 weeks, for me). It’s based on Crown-to-Rump Length or CRL in the first ultrasound, and several body measurements in the second trimester ultrasound, as I read in this paper.

Ultrasound can be used to estimate age, by comparing measurements against average fetal growth curves. Crown-Rump Length is measured in the first trimester. Later, they measure the length of the femur, abdominal circumference, head circumference, and diameter across the head (bi-parietal diameter).

Anyway, so what Julie was effectively telling me is, according to the hospital, I was only one day late at the time I talked to her. Apparently, St. Luke’s considers this the most accurate calculation, and will structure its interpretation of whether you are pre- or post-date around that.

The ramifications immediately elated me. I can go to 43 weeks.

Of course, I birthed Calvin a week ago today. He’s perfectly healthy, and the stress of the medically mandated finish line is lifted.

But that just makes the whole Due Date Thing even more confusing! Did I go into labor roughly “on time” or a week late?

And hey, St. Luke’s? I came in on September 25th to “pre-admit” myself to Labor and Delivery to make sure I had an easy time of transferring if the need arose. I’m in your system. If the ultrasound due date calculation is now your gold standard for labor admissions, why did it take leaving a message for a smart, savvy nurse-midwife, who was only prompted by my asking for a fetal non-stress test, for this calculation to be run at all?

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