Second Trimester Routine Visits
What I’m talking about is a sizeable weight. This isn’t such a problem in the early second trimester, but by about 22 to 24 weeks, you will start to notice this effect. This is why your doctor will tell you to not sleep flat on your back. Your doctor is afraid that although the hypotension may go unnoticed in your sleep, the decreased blood flow to the uterus under less pressure will decrease nutrition and oxygenation to your baby. This is probably not the disaster it seems; otherwise there would be a lot of disasters about. But the mechanics of the physiology are rock solid and make sense. So do everybody a big favor, including your baby, and don’t do it.
Depending on body shape, this particular effect may not present until the late third trimester. But it’s worse the bigger your baby gets. Ultrasound in late pregnancy, with your lying flat on your back, often is interrupted by feelings of nausea. The cure for this is flipping to one side.
The fundal height is just that – the height of the fundus. You doctor will measure from the top of your pubic bone to the curve of the top of the uterus. It’s generally measured in centimeters, and it’s a measurement, as you might suspect, that will increase as your pregnancy continues toward your due date. The fundal height is generally a diagnostic tool held over from the days before ultrasound, but it is still useful in large clinics where the same patient may not get the same doctor twice in a row for her prenatal visits. In those settings it provides some frame of reference for the continuity of the documentation throughout the pregnancy.
There is no measurement more exact than ultrasound, and even this isn’t perfect. But the fundal height, recorded with each visit, is even more inaccurate. Some obstetricians in private practice who see the same patients over and over (small and solo practices) don’t even record it, but merely record whether the size of the uterus is compatible with the gestational age. A physician who is familiar with her patients will generally know when a baby isn’t growing right during the many visits, and if there is suspicion of a growth restricted baby or an LGA (large for gestational age baby), then the standard of care to sort out any worries is ultrasound – not a fundal height.
But the fundal height is very useful in the larger clinics, because many different doctors will see a patient before the due date. Because there needs to be at least some objective frame of reference among the different doctors, the fundal height is still a good idea. It’s not great, but is easy and free. Ultrasound would make more academic sense, but is prohibitive from a cost standpoint when attempted on every visit. Like no two scales reading the same weight the same, also no two doctors are going to measure the same fundal height exactly the same. But if a different doctor gets a discrepancy that’s wildly different from what was recorded by the previous doctor, then ultrasound is justified. This is not very exact science, but it works remarkably well in the larger clinics.
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