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TWINS

TWINS. Identical/Fraternal Twins. Identical (monozygotic) twins form when a single fertilized ovum splits into two. Approximately 1 in 3 twins are identical. Fraternal (dizygotic) twins form when two ova are fertilized by two sperm. Approximately 2 in 3 twins are fraternal.

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TWINS

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  1. TWINS

  2. Identical/Fraternal Twins • Identical (monozygotic) twins form when a single fertilized ovum splits into two. • Approximately 1 in 3 twins are identical. • Fraternal (dizygotic) twins form when two ova are fertilized by two sperm. • Approximately 2 in 3 twins are fraternal.

  3. Identical Twins…

  4. Fraternal Twins…

  5. Factors That Increase The Odds Of Having Twins: • Advancing age of the mother – women in their 30s and 40s have higher levels of the sex hormone estrogen than younger women, which means that their ovaries are stimulated to produce more than one egg at a time.

  6. Number of previous pregnancies – the greater the number of pregnancies a woman has already had, the higher her odds of conceiving twins.

  7. Heredity – a woman is more likely to conceive fraternal twins if she is a fraternal twin, has already had fraternal twins, or has siblings who are fraternal twins.

  8. Race – Black African women have the highest incidence of twins, while Asian women have the lowest.

  9. Assisted reproductive techniques – many procedures rely on stimulating the ovaries with fertility drugs to produce eggs and, often, several eggs are released per ovulation.

  10. Gestation For Twins • The normal length of gestation for a single baby is around 40 weeks. However, gestation for twins, either identical or fraternal, is usually around 35 weeks. (Usually accompanied w/ lower birth weight). • This shorter time is due to the increased demands on the mother’s body, and the inability of the babies to receive all the nutrients they need in utero.

  11. Data… The average twin pregnancy lasts 35 weeks. Triplet pregnancies average 33 weeks, and quad pregnancies average 29 weeks. Keep in mind… Premature babies born between 34 and 37 weeks generally do very well. Babies born before 28 weeks may survive, but they'll need intensive medical care and a little luck.

  12. Conjoined Twins • Conjoined twins are identical twins whose bodies are joined in utero. • A rare phenomenon, the occurrence is estimated to range from 1 in 50,000 births to 1 in 200,000 births, with a somewhat higher incidence in Southwest Asia and Africa.

  13. Chang and Eng Bunker May 11, 1811 – January 17, 1874 in Siam (now Thailand).

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