Raising Twins: What Parents Want to Know (and What Twins Want to Tell Them)
288
Raising Twins: What Parents Want to Know (and What Twins Want to Tell Them)
288eBook
Available on Compatible NOOK devices, the free NOOK App and in My Digital Library.
Related collections and offers
Overview
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
Product Details
| ISBN-13: | 9780062038296 |
|---|---|
| Publisher: | HarperCollins |
| Publication date: | 12/20/2011 |
| Sold by: | HARPERCOLLINS |
| Format: | eBook |
| Pages: | 288 |
| File size: | 5 MB |
About the Author
Jill Alison Ganon is a writer and editor residing in Los Angeles.
Read an Excerpt
Chapter I
together, walking together, and riding together. That's all."
The Biology of Twinning and Twin Development in Utero
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 TwinningDizygotic 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:
- The use of infertility technologies, assisted reproductive technologies (ART). The use of the latest infertility treatments has greatly increased the chances of having multiples. When irregularity in ovulation is suspected as a cause of infertility, a woman may be treated with medication, such as Pergonal or Clomid, designed to stimulate the development of multiple follicles within her ovaries. In turn, these follicles may produce multiple eggs, resulting in a greater likelihood of twin or higher order multiple pregnancies.
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.
- Women delaying the start of their families. With an increase in maternal age, there is more likely to be an increasing secretion of follicle stimulating hormone (FSH), which leads to ovulation of two ova, thereby producing dizygotic (DZ) twins- Women between the ages of 35 and 39 have a greater likelihood of having multiples than younger women.
- Genetic factors. There is a genetic predisposition for dizygotic twinning-that is, the tendency to release more than one egg at a time. This tendency can be inherited from either the mother's or the father's genes. Since only women can produce eggs, this genetic predisposition displays itself on only the mother's side.
- Racial factors. Dizygotic twinning among the numerous races living in the United States varies considerably.
Blacks: 25.8 per
1,000 births Alaskan natives:
24.9 per 1,000 births
Caucasians: 19.6 per 1,000 births
American Indians: 18.8 per 1,000 births
Japanese: 17 per 1,000 births
Hawaiians: 15.3 per 1,000 births
Filipinos: 13.2 per 1,000 births
Chinese: 11.,2 per 1,000 births.
Access to infertility treatment is closing the gap among the races with regard to the rate of dizogotic twinning.
- Mothers of dizygotic twins are usually taller and weigh more than mothers of monozygotic twins.
- Women who have given birth to dizygotic twins have increased levels of FSH.
- Seasonal fluctuations. It has been reported that the length of daylight may affect the production of follicle stimulating hormone (FSH). Some countries in the northern hemisphere, where there are long summer days, such as northern Finland and northern Japan, have higher dizygotic twin conceptions during the month of July. But there is no consistent evidence.
- Nutrition. Malnutrition decreases the twinning rate. During difficult economic times, such as those caused by famine, there tends to be more malnutrition and lower dizygotic twinning rates. In Yoruba, where the twinning rate is high, their diet (yams) may cause stimulation of the follicle stimulating hormone (FSH).
- Environment. Some reports say that toxic substances in the water and food supply can affect the production of sperm and decrease dizygotic twinning. On the other hand, in regions that have high levels of polychlorinated hydrocarbons, there is an increase in twinning, leading some to believe that there may be some "estrogen-like effects" in some pollutants.
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...