How to best establish prenatal paternity?
June 20, 2010 4:02 PM Subscribe
I am embroiled in a paternity conundrum. Several questions enclosed.
First, the easy one: is it standard to date fetal age by conception or by conception + 2 weeks (aka end of period prior to the conception)? It seems like both are used but often an Xth week of pregnancy is noted without saying which formulation is meant.
2.
How well can an ultrasound establish conception date? I see some mothers on forums saying that they were told their fetus was X weeks and Y days old. Is a fetal age really observerd so precisely? What is the degree of confidence? What are the ranges that they're likely to offer? Does this measurement become easier and/or more difficult at different stages of early development?
3.
How dangerous are the CVS and Amniocentesis tests for paternity? They seem to be done routinely when parents feel a strong need to test against Downs or other genetic problems. But the "slight chance" of miscarriage seems to suggest that a paternity question is not an ethicially valid reason for doing these. How slight is the chance of harm for mother or fetus for each of these? I can't find numbers.
4.
How accurate are the "non-invasive" DNA paternity tests? I see a ton of places offering to test using mother's blood and potential father's cheek swab after 13 weeks (or do they mean 11 weeks since conception?). The only info I find is on the sites advertising the services. Where can I find independent testing/auditing of this method?
Because the issue of paternity is extremely important to her decisionmaking from here on out, she's talked them into doing an ultrasound -- even though conception was only 4.5 to 7.5 weeks ago (her previous cycle's timing was not keenly observed).
What will we know afterwards, and how well will we know it?
First, the easy one: is it standard to date fetal age by conception or by conception + 2 weeks (aka end of period prior to the conception)? It seems like both are used but often an Xth week of pregnancy is noted without saying which formulation is meant.
2.
How well can an ultrasound establish conception date? I see some mothers on forums saying that they were told their fetus was X weeks and Y days old. Is a fetal age really observerd so precisely? What is the degree of confidence? What are the ranges that they're likely to offer? Does this measurement become easier and/or more difficult at different stages of early development?
3.
How dangerous are the CVS and Amniocentesis tests for paternity? They seem to be done routinely when parents feel a strong need to test against Downs or other genetic problems. But the "slight chance" of miscarriage seems to suggest that a paternity question is not an ethicially valid reason for doing these. How slight is the chance of harm for mother or fetus for each of these? I can't find numbers.
4.
How accurate are the "non-invasive" DNA paternity tests? I see a ton of places offering to test using mother's blood and potential father's cheek swab after 13 weeks (or do they mean 11 weeks since conception?). The only info I find is on the sites advertising the services. Where can I find independent testing/auditing of this method?
Because the issue of paternity is extremely important to her decisionmaking from here on out, she's talked them into doing an ultrasound -- even though conception was only 4.5 to 7.5 weeks ago (her previous cycle's timing was not keenly observed).
What will we know afterwards, and how well will we know it?
Consider me a cynic, but if you're at the point where the difference of a week here and there would drastically change the outcome of the paternity test, you should probably operate as if you're not the father. It's extremely difficult to contest paternity once you've admitted to it, so please protect yourself at this stage.
posted by Oktober at 4:50 PM on June 20, 2010 [2 favorites]
posted by Oktober at 4:50 PM on June 20, 2010 [2 favorites]
The measurement of fetal age via ultrasound is much more accurate early in a pregnancy, and steadily declines over time. I don't know the exact degree of confidence, I am sure it's googleable, but I had one around 7 weeks and it was very accurate in the dating.
The week of the pregnancy always includes the "extra" two weeks-- from the first day of the period prior to conception (not the last as you mention). Thus depending on when in her cycle she ovulates there could be some play in the date of conception.
posted by miss tea at 5:07 PM on June 20, 2010
The week of the pregnancy always includes the "extra" two weeks-- from the first day of the period prior to conception (not the last as you mention). Thus depending on when in her cycle she ovulates there could be some play in the date of conception.
posted by miss tea at 5:07 PM on June 20, 2010
1. Pregnancies are historically dated from 1st date of last menstrual period, since this is the most easily ascertainable date for most women who are having intercourse regularly. Women whose periods are routinely longer or shorter than average may wish to discuss how this effects the estimated date of delivery with their OB.
2. Ultrasound is very good at estimating GA (gestational age) especially for women with 28 day cycles and during the first trimester (up to about 9-12'ish weeks). After that fetal growth trends are averaged among various head, abdomen and femur measurements which may reflect ethnic, parental, and individual growth patterns (i.e., the fetus with Jack the Giant as dad will measure differently than the fetus with Tom Thumb as the father. Fetuses with overgrowth/undergrowth syndromes may be detectable by third trimester sonograms.)
3. CVS and amnio are both reasonably safe, with less than a 1/200 risk of miscarriage due solely to the procedure. Experienced practitioners may well have less than 1/500 or less than 1/1000 pregnancy loss rate. As long as you are aware that the procedure could end in miscarriage, most practititioners will not refuse a paying customer. Your insurance company is a different issue. The CVS/amnio are likely to be several times more expensive than the paternity testing.
4. IMO, paternity testing should always involve a specimen from the child, the mother and all purportedly possible fathers. This allows the mother's data to serve as a control and the father's to be used to determine a relative cumulative likelihood of paternity rather than just a likely or unlikely.
Close relatives such as sibs or cousins may not be distinguishable as to likelihood of fatherhood without testing a greater than usual number of markers. In such cases, the timing of the conception may be useful information.
Be aware that there are differences in quality of labs, and espeically if a "legal" result is desired.
posted by beaning at 5:11 PM on June 20, 2010
2. Ultrasound is very good at estimating GA (gestational age) especially for women with 28 day cycles and during the first trimester (up to about 9-12'ish weeks). After that fetal growth trends are averaged among various head, abdomen and femur measurements which may reflect ethnic, parental, and individual growth patterns (i.e., the fetus with Jack the Giant as dad will measure differently than the fetus with Tom Thumb as the father. Fetuses with overgrowth/undergrowth syndromes may be detectable by third trimester sonograms.)
3. CVS and amnio are both reasonably safe, with less than a 1/200 risk of miscarriage due solely to the procedure. Experienced practitioners may well have less than 1/500 or less than 1/1000 pregnancy loss rate. As long as you are aware that the procedure could end in miscarriage, most practititioners will not refuse a paying customer. Your insurance company is a different issue. The CVS/amnio are likely to be several times more expensive than the paternity testing.
4. IMO, paternity testing should always involve a specimen from the child, the mother and all purportedly possible fathers. This allows the mother's data to serve as a control and the father's to be used to determine a relative cumulative likelihood of paternity rather than just a likely or unlikely.
Close relatives such as sibs or cousins may not be distinguishable as to likelihood of fatherhood without testing a greater than usual number of markers. In such cases, the timing of the conception may be useful information.
Be aware that there are differences in quality of labs, and espeically if a "legal" result is desired.
posted by beaning at 5:11 PM on June 20, 2010
I have never been to a doctor who has dated fetal age by conception. Even when I had a very early ultrasound (5w3d) it was based on the last period method, not conception. It was about 6 days out by LMP method. It isn't an exact science by any means. Earlier scans are more accurate but because there is such a large number of non-standard conception/ovulation/implantation times, I wouldn't bet on any of them to rule on exactly when the baby was conceived. Even with that early ultrasound and knowing when I'd gotten my period and getting morning sickness from implantation, *I* still have some doubts about which bout of sex made our daughter and there were only two bouts to choose from.
posted by geek anachronism at 5:30 PM on June 20, 2010
posted by geek anachronism at 5:30 PM on June 20, 2010
I don't think you can get very far with these questions without talking to a medical professional. Gestational age is charted from the last menstrual period. It may or may not match the observational age they get when they do the ultrasound. These dates are essentially meaningless if you're trying to figure out 'was it that weekend or that weekend'.
To know for certain, you really need genetic material and to talk to someone about whether or not an amnio or CVS can provide enough to type a dad. If the mom doesn't want to take the risk, there's nothing you can do but see the pregnancy through and do the genetic tests afterward.
I'm really sorry -- it sounds terribly stressful and I can imagine how drop dead important it is to figure this out as soon as possible. For me, personally, I'm comfortable with amnio -- I feel like the miscarriage risks are minimal and it can tell you important information--but other women are not and if Mom in this case won't take the risk you will have to breath deeply and wait.
posted by A Terrible Llama at 5:40 PM on June 20, 2010
To know for certain, you really need genetic material and to talk to someone about whether or not an amnio or CVS can provide enough to type a dad. If the mom doesn't want to take the risk, there's nothing you can do but see the pregnancy through and do the genetic tests afterward.
I'm really sorry -- it sounds terribly stressful and I can imagine how drop dead important it is to figure this out as soon as possible. For me, personally, I'm comfortable with amnio -- I feel like the miscarriage risks are minimal and it can tell you important information--but other women are not and if Mom in this case won't take the risk you will have to breath deeply and wait.
posted by A Terrible Llama at 5:40 PM on June 20, 2010
Yeah, gestational age is counted from the last menstrual period. It can be adjusted by early ultrasound, at which point it becomes a weird hybrid thing -- the actual age of the embryo is determined in days *from fertilization*, which is not the same as days from intercourse. For circumstances in which ovulation/fertilization occurred on other than day 14, the gestational age is dated from two weeks prior to the ovulation/fertilization day.
Early, high-resolution ultrasound is pretty crazy accurate in showing age of the embryo. But there's a lot of stuff that can happen between intercourse, ovulation, and implantation that can affect the timing between the embryo's age and the act that caused the conception. Could be the same day, could be a week later.
If you live in a big city with a big hospital, CVS/amnio is pretty damn safe. The non-invasive paternity tests are not quite so bad as to be useless if it's mom's first pregnancy, but awfully near, and if she's had a miscarriage, abortion, or term pregnancy before, they're utterly useless.
If you have an actual fetal tissue sample (CVS/amnio) and a reputable lab, paternity should be able to be determined fairly definitively -- unless you have some weird mosaicism situation going on, in which case all bets are off.
posted by KathrynT at 6:02 PM on June 20, 2010
Early, high-resolution ultrasound is pretty crazy accurate in showing age of the embryo. But there's a lot of stuff that can happen between intercourse, ovulation, and implantation that can affect the timing between the embryo's age and the act that caused the conception. Could be the same day, could be a week later.
If you live in a big city with a big hospital, CVS/amnio is pretty damn safe. The non-invasive paternity tests are not quite so bad as to be useless if it's mom's first pregnancy, but awfully near, and if she's had a miscarriage, abortion, or term pregnancy before, they're utterly useless.
If you have an actual fetal tissue sample (CVS/amnio) and a reputable lab, paternity should be able to be determined fairly definitively -- unless you have some weird mosaicism situation going on, in which case all bets are off.
posted by KathrynT at 6:02 PM on June 20, 2010
My two girls were ivf. We knew their conception date down to the second and had earlier blood tests and ultrasounds than normal people do. And STILL we were not able to categorically tell how old the embryos were... well, of course we knew... but the other methods did not 100% agree.
Wait till the baby is born, then do a swab. Anything more invasive is not 100% safe before birth, and is not medically necessary.
posted by taff at 3:23 AM on June 21, 2010
Wait till the baby is born, then do a swab. Anything more invasive is not 100% safe before birth, and is not medically necessary.
posted by taff at 3:23 AM on June 21, 2010
If the identity of the father will determine whether to abort or not, she should have the CVS done.
posted by crankylex at 3:33 PM on June 21, 2010
posted by crankylex at 3:33 PM on June 21, 2010
Sounds like there would be a lot of drama if the wrong baby was born so I'll second crankylex. Theoretical conception date is a really poor determinate of father hood if there is anything approaching overlap because of the long life of both sperm and eggs.
posted by Mitheral at 1:22 PM on June 22, 2010
posted by Mitheral at 1:22 PM on June 22, 2010
This thread is closed to new comments.
I think ultrasound can help a great deal, but nothing to do with human reproduction is especially precise in my experience as someone trying to get pregnant. Growth rates of fetuses vary, just like growth rates of babies do.
The general risk of miscarriage for amnio is usually given at about 1% and CVS is apparently a little higher, but it has declined over time. How old is the mom? If she's over 35, it makes sense to have the test anyway.
Dunno about the last one but do know that the industry isn't especially regulated.
posted by Maias at 4:40 PM on June 20, 2010