- Shopping Bag ( 0 items )
Raising Twins guides you through the physical, emotional, and cognitive developmental differences and challenges specific to twins. Straightforward and reassuring, this book addresses the key issues that impact twins from babyhood all the way through adolescence: Sharing and comparisons Competition and rivalry The "secret language" of twins The good twin/bad twin myth Teen-specific issues like dating and applying for college And much more including lively, candid discussions ...
Raising Twins guides you through the physical, emotional, and cognitive developmental differences and challenges specific to twins. Straightforward and reassuring, this book addresses the key issues that impact twins from babyhood all the way through adolescence: Sharing and comparisons Competition and rivalry The "secret language" of twins The good twin/bad twin myth Teen-specific issues like dating and applying for college And much more including lively, candid discussions with twins and their parents.
When done the old-fashioned way (that is to say, in a candlelit room, without the presence of a laboratory technician), a man's sperm meets a woman's egg (ovum), and the fertilized ovum enters the uterine cavity and is implanted there. The cells then begin to differentiate. Some form the placenta, while others create the sac made up of two layers: an outer layer (the chorion) and an inner layer (the amnion) in which the embryo (the stage in human development between the ovum and the fetus) will reside throughout its gestation. The cells will continue to develop until the embryo becomes a fetus after 8 weeks gestation. Approximately 28 weeks later, the fetus, now a baby, is delivered into your loving family.
In order for twins to occur, two embryos develop simultaneously in a woman's uterus. If we translate the statistics below into the likelihood of a woman in the United States giving birth to twins, we come up with a figure of approximately 1 in 39 being doubly blessed in the delivery room.
If you are the parent of twins, the great majority of you know that you have given birth to two children who developed in the uterus at the same time from the same impregnation. But that is just the very beginning of the story. Twinning actually occurs in one of two ways, resulting in either dizygotic (fraternal) or monozy, gotic (identical) twins. Thediagram below should make the fundamental biological difference between the two types of twinning very clear.Dizygotic and Monozygotic Twinning
Dizygotic twinning occurs when two different ova, occurring from two separate follicles, are fertilized by two separate sperm. Dizygotic twinning accounts for approximately two thirds of all twin births. Dizygotic twins each have their own separate placenta, as well as two chorions (dichorionic) and two amnions (diamniotic). Sometimes the placentas are implanted close together and may fuse, thereby giving the appearance of one placenta, when in actuality there are two. If the determination of zygosity is performed by a cursory look at the placentas, an inaccurate diagnosis may be given. Dizygotic twins share the same degree of genetic similarity as any two siblings born at different times to the same set of parents, except for one major difference-dizygotic twins share the same intrauterine environment for approximately seven to nine months. This closeness and sharing from fertilization to birth and after creates an important bond to many dizygotic twins.
There are several factors that are believed to influence dizygotic twinning, though no one of these can be said to be its single cause. The following are some causes of dizygotic (fraternal) twinning:
Technologies that transfer eggs into the uterus or fallopian tubes, such as in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT), can produce dizygotic multiples. On occasion, the ovum splits and may result in monozygotic twinning.
Access to infertility treatment is closing the gap among the races with regard to the rate of dizogotic twinning.
Monozygotic twinning is the result of one egg being fertilized by one sperm, which then splits into two separate zygotes (embryos) some time within the first 14 days after fertilization. The earlier the split, usually before implantation (first five days), the more likely the occurrence of two separate placentas. Each placenta has one chorion (outer membrane) and one amnion (inner...