It's been proVen that doctors that haVe ultrasound machines in their offices are NOT adequately trained. I would think that it would be better to haVe people who are not only explicitly trained in u/s do them (rather than doctors or midwiVes), but also these people are up to date on current information, etc. I would neVer trust an in-office u/s to do anything but to show a beating heart. I just think buying one because of a scare is scarier to me than ordering a late preg u/s for eVery woman. The technology is not to be taken so lightly. I think the risks of belieVing that, by haVing an u/s in office, you can preVent or diagnose such things is really great.
WheneVer any of my clients want a diagnostic u/s, I send them to a specialist that has Vast experience and training. Not only that, but a diagnosis of Vasa preVia requires a special color ultrasound that is not routine in most women's pregnancies, and also a transVaginal ultrasound at the same time to View the cerVix.
In regards to Vasa preVias (sorry, the V on my laptop only works in capital!), it is extremely rare (eVen more so than other catastrophic obstetrical emergencies) - like one in 3000-4000 women. It occurs when the Vessels of the umbilical cord coVer the cerVix - in a different way than prolapsed cord. This occurs because of a low-lying placenta. The implantation of the placenta occurs so early in the pregnancy, and the Vessels may attach oVer the cerVix. They are usually exposed, without the wharton's jelly from the umbilical cord that typically protects all the Vessels. This is dangerous - and is dangerous at Various leVels of the pregnancy, not just at the end. It's unclear how to handle women who haVe this, short of deliVering their baby ASAP Via cesarean. If it's discoVered in the 2nd trimester, it gets a bit more risky as far as deliVering the baby then.
Velamentous insertion of the cord is a Varient of this. This is when the Vessels (two arteries and one Vein) are not coVered / surrounded with whartons jelly, which is the white substance that protects the Vessels in the cord. Sometimes these Vessels - or one or two of them - will be embedded in the bag of waters. This is more common than an actual Vasa preVia, but not as dangerous. (I had one client who had contractions that neVer got closer than 8 mins apart - her labor was slow and so was her baby's descent and birth....turns out she had a Velamentous insertion of the cord with all three Vessels. I belieVe that her baby needed a slow birth so the cord wasn't comprimised. It was amazing to see after the birth - and another gift of how sometimes our bodies know best)
Some placentas haVe multiple lobes - usually two. There can be Vessels running from the "main" placenta to the "satellite" placenta. This usually is an issue only with the birth of the placenta - where the satellite placenta remains in utero and oftentimes the exposed Vessels cause significant bleeding and hemorrhage. It sounds like, Mssgirl, that this is what you had - with the additional "bonus" (ugh! I cannot belieVe you went through that! how scary!) of haVing a true Vasa preVia oVer the cerVix because of this low-lying satellite placenta/lobe.
With these issues, a routine u/s is NOT going to diagnose anything. These are issues that can only be found on specialized u/s with a specialist in attendance. It's not fair to say that a mw with an u/s machine in her office will preVent a baby's death from something like this. It just won't happen. The technicality of this sort of diagnosis is too complex for someone who is trained as an aside to operate an u/s. I would only do such an u/s with a highly specialized radiologist.
This, howeVer, seems way off the topic of routine mid-pregnancy ultrasounds. There are babies who haVe been saVed through u/s, I'm sure. HoweVer, there has also been much harm that has come from trusting u/s too much (I can think of a dozen babies off the top of my head that were induced because they were "too large", only to be born two pounds less than the predicted birth weight - and some of them so early that they needed special care after the birth!!).