A large for date fetus is when the fetal weight is more than expected by being above the 90th percentile. A large fetus could be due to: polyhydraminous, large placenta (hydrops), macrosomia (skin thickening), or twin/multiple pregancies.
When a mother exhibits a twin pregancy test, automatically she is high risk OB. The most common reason for having twins is by either infertility treatment or genetic. Twins can be described by two types: identical and non-identical.
Identical twins (girl-girl) are monozygotic (one zygote) and have two membranes with the possibility of one chorionic membrane. Describing the membranes (chorionic, amniotic) can be broken down by the following:
1) Dichorionic, Diamniotic (before day 5)
2) Monochorionic, Diamniotic (btw day 5-9, most common)
3) Mochorionic, Monoamniotic (btw day 9-13)
4) Conjoined (after day 13)
Note that if Dichorionic and Diamniotic, then both membranes would have two placentas. However, if Monochorionic and Diamniotic, then one membrane (Mono) would have one placenta whereas the other (Di) would have two placentas. Another way to distinguish between Mono- and Di- is to look at the thickness of the membranes. Mono- will have a thin membrane (one) whereas Di- will have a thick membrane (two). Below are images describing the two membranes.
When a mother exhibits a twin pregancy test, automatically she is high risk OB. The most common reason for having twins is by either infertility treatment or genetic. Twins can be described by two types: identical and non-identical.
Identical twins (girl-girl) are monozygotic (one zygote) and have two membranes with the possibility of one chorionic membrane. Describing the membranes (chorionic, amniotic) can be broken down by the following:
1) Dichorionic, Diamniotic (before day 5)
2) Monochorionic, Diamniotic (btw day 5-9, most common)
3) Mochorionic, Monoamniotic (btw day 9-13)
4) Conjoined (after day 13)
Note that if Dichorionic and Diamniotic, then both membranes would have two placentas. However, if Monochorionic and Diamniotic, then one membrane (Mono) would have one placenta whereas the other (Di) would have two placentas. Another way to distinguish between Mono- and Di- is to look at the thickness of the membranes. Mono- will have a thin membrane (one) whereas Di- will have a thick membrane (two). Below are images describing the two membranes.
In non-identical twins (boy-girl), the membranes are "always" Dichorionic, Diamniotic (look at first picture). Non-identical twins are dizygotic (two zygotes). A good way to distinguish if both membranes are Di-Di is to look for "twin peak" sign, which is a traingular projection of placental tissue from the placental surface extending to the intertwin membrane. Below is an ultrasound image of the "twin peak" sign seen btw 10-14 wks GA.
Below are ultrasound images of twin pregnancies
9 Week Monochorionic, Diamniotic Twins
6 Week Dichorionic, Diamniotic Twins
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