Describe fraternal twinning, including maternal factors linked to fraternal twinning

Question

What will be an ideal response?

Answer 1

Fraternal, or dizygotic, twins, the most common type of multiple birth, result from the release and fertilization of two ova. Genetically, they are no more alike than ordinary siblings. Older maternal age, fertility drugs, and in vitro fertilization are major causes of the dramatic rise in fraternal twinning and other multiple births in industrialized nations over the past several decades. Specific maternal factors linked to fraternal twinning include:
– Ethnicity. Occurs in 4 per 1,000 births among Asians, 8 per 1,000 births among whites, and 12 to 16 per 1,000 births among blacks
– Family history of twinning. Occurs more often among women whose mothers and sisters gave birth to fraternal twins
– Age. Rises with maternal age, peaking between 35 and 39 years, and then rapidly falls
– Nutrition. Occurs less often among women with poor diets; occurs more often among women who are tall and overweight or of normal weight as opposed to slight body build
– Number of births. Is more likely with each additional birth
– Fertility drugs and in vitro fertilization. Is more likely with fertility hormones and in vitro fertilization, which also increase the chances of bearing triplets, quadruplets, or quintuplets