MikeH said:
Speaking of ultrasouds, most places offer 4-D (don't ask me why it is called 4-D
) pictures of your baby/babies. It is a tad bit pricey but it is pretty neat as well. You really get a startling glimpse at your wee ones(much better than just the regular ultrasounds pics). I would recommend it when your wife is aways along as it makes for a better product for obvious reasons. (We have some of them holding hands and one of my daughter with my sons foot "in" her mouth (of course both sacks seperate them but you wouldn't know from looking).They usually give you quite a few pictures, videos...etc, all on CD and/or DVD.
You should consider it.
-Mike
If they are identical twins, they may share the same placenta (sac). This is from a twin site and I thought Zim might want to read up on it:
There are two types of twins, monozygotic, identical, and di-zygotic - fraternal.
Fraternal twins come from two embryos that began as two eggs and two sperm, and can be either girl/boy, boy/boy or girl/girl. Since they do not share more than a regular sibling relationship as far as DNA is concerned, they can be opposite sexes, different blood types, different hair colors, different eye colors and different body shapes. One thing that is virtually guaranteed is that they will not share a placenta, as the placenta is formed when the embryo implants into the wall of the uterus.
Identical twins come from single egg and sperm that form 1 embryo, that then divides into two. Because they share identical DNA, they have many basic architectual components that, unless there is a congenital accident (genetic accident that is not hereditary) they will be the same sex, have the same eye color, same hair color, same blood type, and basically the same body shape. However, Identical twins can have many different placental configurations... if the embryo divides before it starts implanting in the uterine wall, then both resulting embryos will implant on their own. Then they will each have their own completely seperate gestational sac, which is comprised of the placenta and the bag of waters.
If the embryo divides after implantation, and the placenta has already been started, then there will only be 1 gestational sac. Usually that sac will be divided into two compartments giving each baby its own "room". In a small number of cases, the embryo divides so late that the bag of water has already been formed, so both babies have to share a room. Two babies in a single gestational sac with a dividing membrane is called monochorionic - diamniotic. If the dividing membrane is missing it is called monochorionic - monoamniotic.
Fraternal twins will always be dichorionic. Identical twins can be dichorionic (8% of all pregnancies, 25% of identical twin pregnancies) Mono-chorionic - (75% of all identical twins) and mono-amniotic - less than 1% of identical twin pregnancies - and this includes conjoined twins.
Sometimes it is possible to tell from u/s if there is one gestational sac or two. if the u/s are done early enough, the fact that there is space between two gestational sacs is pretty evident. Once there is no space, it is a little harder but not impossible. The membrane that holds in the amniotic fluid is actually two membranes fused together, the chorion and the amnion.
If the babies are in two seperate gestational sacs the membrane dividing them, is actually two membranes and will therefore be nearly 4 times as thick as in the case of twins that share a gestational sac, but have the single layer of amniotic membrane dividing them. The dividing membrane, would be the amnion/chorion of one pushed up against the chorion/amnion of the other. If the u/s tech can measure a non dividing membrane area, and compare it to the one, it can be evident that the dividing one is either thicker or thinner than the sac at other places.
Thats how they tell from u/s. But the important thing to note is that when they don't share a sac they can be either fraternal or identical, although the odds are higher that they are fraternal. If they share a sac they can ONLY be identical (execept in one rare documented case)
But this is only as reliable as the u/s technician and the equipment being used. Thats why a good examination, not of the placenta, but of the membranes, is often used by path labs to determine what the configuration was. You can't just look at one huge placenta and say it was originally 1 or 2 that grew together. They have to rely on the membrane remnants. And even then, there are occasions where even that has been wrong.
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