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Convention 2010 Peninsula Mothers of Multiples & SouthEastern VA Parents of Multiples Club are hosting the 2010 annual MAPOM Convention. |
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MAPOM BOARD 2008
PRESIDENT 2006:
Susan Everingham
Vice President
Diana Knollman
SECRETARY:
Petra Funk
TREASURE:
Melissa DeHaven
WEBMASTER:
Kimberly Cross
Birth Statistics
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National Center for Health Statistics
National Vital Statistics Reports
Adapted from - BIRTHS: FINAL DATA FOR 1999
ABSTRACT
Overall birth and fertility rates changed less than one percent in 1999. Teenage birth rates fell 2 to 6 percent. The proportion of multiple births continued to rise; however, higher order multiple births (e.g., triplets, quadruplets) declined for the first time in over a decade, following increases of 13 percent per year during 1990-98. The percent of low birthweight remained at 7.6 percent, while preterm births rose to 11.8 percent. These trends are in large part the result of increases in multiple births.
HIGHLIGHTS
Births in the United States increased less than 1 percent in 1999, to 3,959,417, the second consecutive increase following a 7 percent decline from 1990 to 1997. The birth rate declined slightly in 1999 to 14.5 births per 1,000 total population, matching the record low reached in 1997.
MULTIPLE BIRTHS
The number of multiple births in twin deliveries continued to climb in 1999, rising 3 percent to 114,307 births. The twin birth rate (the number of twin births per 1,000 live births) was also up for 1998-99, rising 3 percent, to 28.9 per 1,000 births. Since 1980 the number of twins has risen 67 percent (from 68,339), and the twin birth rate by 53 percent (from 18.9).
Twin birth rates rose between 1998 and 1999 for nearly all age groups, and for non-Hispanic white (31.5 per 1,000) and non-Hispanic black women (32.1). A small decline in the twinning rate for Hispanic women was reported (20.1).
Historically, twin birth rates have been highest for mothers 35-39 years of age. In 1999 however, twin birth rates rose steadily with maternal age and were highest for women aged 50-54 years. Since 1990, the twin birth rate has risen 80 percent among women 40-44 years of age (from 24.7 to 44.5 per 1,000), and almost 600 percent among women aged 45-49 years (from 23.8 to 155.7), compared to only a 6 percent rise for women under age 20 years (14.3 to 15.2). Comparable trend data are not available for women aged 50-54 years, but in 1999 more than a third of births (34 percent) to women in the oldest age group were born in a twin delivery.
Multiple births present substantial perinatal risk to both mother and infant, and risk increases with plurality. Mothers of multiples suffer more ante- and postpartum complications than singletons and their infants are born considerably smaller; on average, twins weight about a third less, and triplets about half of singletons.
Massachusetts reported the highest triplet birth ratio for 1992-94, 215.9, more than twice as high as that of the Nation as a whole. Ratios were also comparatively high for New Hampshire, New Jersey, and Iowa.
The twin rate has been increasing. Recent statistics from the National Center for Health Statistics in the United States in 1999 showed that there were 114,307 babies born as twins (or 57,154 sets), 6,742 as triplets, 512 as quadruplets, and 67 as quintuplets and other higher order multiples. The twinning rate is 28.9 per 1,000. This translates into a probability of having twins as one in 35 and of having higher order multiples as one in 541. This shows a 3 percent increase in the twin rate from 1998 to 1999. Since 1980 the number of twins has risen 67% and the twin birth rate by 53%. The major causes of the increase are older-aged women having babies and also fertility treatments, which account for 80 percent of the increase.
INCIDENCE OF TWINS BY TWIN TYPE
The rate of identical twins is constant at approximately four per thousand. It is remarkable that the incidence of identical twins remains the same no matter where a person lives, and it has remained the same throughout history. The rate of fraternal twins, on the other hand, can change depending on where a person lives, the mother's age, etc. Fraternals account for the differences in the twin rate, the fraternal rate being approximately 22.8 per thousand in the world.
Any given mother would have a better chance of having fraternal twins, as there are two thirds more fraternal or dizygotic twins than identical or monozygotic twins. However, your own chance of having twins depends on your personal history, age, race, and many other factors.
FACTORS AFFECTING THE TWINNING RATE
Only fraternal twins tend to run in families. Identical twins happen by "chance" and can happen to anyone, regardless of whether there are twins in the family or not.
Many people believe that twins "skip a generation." Twinning is passed on as a genetic trait and appears in the women only. If you are a female and your mother had fraternal twins, you would have an increased chance of having fraternal twins yourself. Your brothers would not have an increased chance of having fraternal twins themselves, but they may pass the genetic trait on to their daughters who would then have an increased chance of having twins. This makes it appear that twins skip a generation.
For women, twins running in your husband's family appear to have no effect on your chances of conceiving twins. However, this is still being studied. But many physical and environmental factors having nothing to do with heredity can trigger a twin pregnancy. You could still have twins, but they likely would not be caused by any trait in your husband's family.
It is well known that fertility treatments can cause multiple births. This affects only the rate of fraternal or dizygotic twins. These methods use many different types of drugs and treatments. Most of them rely on stimulating ovulation with hormones or, more recently, inserting fertilized eggs into the mother. Fertility treatments are not thought to cause identical or monozygotic twins.
There are also many other factors that increase the rate of fraternal births. They include social habits, maternal age, number of pregnancies, geographic location, seasons, and nutrition.
The incidence of fraternal twins varies by race. Africans have a higher rate, about 16 per thousand, and Asians have the lowest rate, about three per thousand. The rate in Caucasians is about eight per thousand. In the United States the Hispanic twinning rate (20.1 per 1,000) is substantially lower than the rate of non-Hispanic whites (31.5 per 1,000) and that of non-Hispanic blacks (32.1 per 1,000). A well-known tribe in Africa called the Yorubas has the highest twinning rate in the world, one in 22. This increase is due to fraternal twinning, as their rate of identicals is the same as the rest of the world. Their diet consists of large amounts of a particular species of yam (Dioscorea rotundata). This yam contains a high level of a substance similar to the hormone estrogen, which is thought to bring on multiple ovulation.
The older one is, the higher one's chance of having fraternal twins. The twinning rate is doubled for ages 35 to 40 and then decreases again, probably due to a decrease in fertility as one ages. The rate increases again for the age group 45 to 49 years. Older women are having multiples at an increasingly high rate. Since 1990, the twin birth rate has risen 80 percent among women 40-44 years of age (from 24.7 to 44.5 per 1,000) and almost 600 percent among women aged 45-49 compared to only a six percent rise for women under age 20. There were more twins born to women ages 45 to 49 in 1997 than during the entire decade of the 1980s. This, however, accounts for only five tenths of one percent of all twins born, reflecting the relatively fewer births in older women. In other words, you are less likely to give birth over the age of 45. But if you do, there is a 33 percent chance that it will be a multiple birth.
Being well nourished increases the chance of twinning, but the rates drop off with malnutrition. Certain social habits, such as eating certain yams grown in Africa, can increase your chances of twinning. The more pregnancies you have had, the greater are your chances of having fraternal twins. By your fourth or fifth pregnancy, your chance of having twins is four times higher than for your first pregnancy.
Geographically, rates of fraternal twins are greater in northern areas than in those farther south. Also, different races and countries have varied rates of twinning. In the United States, Massachusetts and Connecticut reported the highest proportion of twins, 25 percent higher than the U.S. rate, while Nebraska and New Jersey had twice the national level of triplet and higher births.
The most fraternal twins are conceived in July, the fewest in January. This is thought to be due to the effect of the length of daylight on the secretion of Follicle Stimulating Hormone.
| Type of Birth |  |
1996 | |
1997 | |
1998 | |
1999 | |
2000 | |
2001 | |
2002 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Twins | |
100,750 | |
104,137 | |
110,670 | |
114,307 | |
118,916 | |
121,246 | |
125,134 |
| Triplets | |
5,298 | |
6,148 | |
6,919 | |
6,742 | |
6,742 | |
6,885 | |
6,898 |
| Quadruplets | |
560 | |
510 | |
627 | |
512 | |
506 | |
501 | |
434 |
| Quintuplets/Higher | |
81 | |
79 | |
79 | |
67 | |
77 | |
85 | |
69 |
| Overall Births | |
3,891,494 | |
3,880,894 | |
3,941,553 | |
3,959,417 | |
4,058,814 | |
4,025,933 | |
4,021,726 |
*(Number of babies born)
