37 men who had fathered non-identical twins with a control group of 349 men with normal, healthy sperm. On average, they found that fathers of twins had more normal and motile, or mobile, sperm than the control group. Their sperm counts were also higher, although not significantly.
Just the two of us. Fraternal twins are formed when two eggs meet two sperm in the womb. Each is fertilized independently, and each becomes an embryo. With identical twins, one egg is fertilized by one sperm, and the embryo splits at some later stage to become two.
Now an international research group has found that twin mothers are not actually more fertile than other women. On the contrary, when a woman gives birth several times, the chances increase that at least one of these births will be a twin birth. Twin mothers aren't supermothers, but have been given more chances."
Identical twins share the same genomes and are always of the same sex. In contrast, fraternal (dizygotic) twins result from the fertilization of two separate eggs with two different sperm during the same pregnancy. They share half of their genomes, just like any other siblings.
Dizygotic (DZ) twins, also called fraternal twins, occur when two egg cells are each fertilized by a different sperm cell in the same menstrual cycle.
Factors that increase the chance of twins include: consuming high amounts of dairy foods, being over the age of 30, and conceiving while breastfeeding. Many fertility drugs including Clomid, Gonal-F, and Follistim also increase the odds of a twin pregnancy.
Heredity on the father's side does not increase a couple's odds of having multiples. This is true even if his family is full of multiples. Men, of course, don't ovulate, so even if they've inherited that hyperovulation gene from their parents, it doesn't increase their own odds of conceiving twins.
The Science of Fraternal Twins. Mixed-gender twins are the most common type of fraternals, some 50 percent are boy-girl.
If the egg fertilized the couple were more likely to conceive a baby boy. Female sperm were found to be slower, fitter and would live longer than male sperm so making love earlier in the fertile window meant they would still be alive to fertilize the egg, and more likely to conceive a baby girl.
If more than one sperm fuses—a condition called polyspermy—multipolar or extra mitotic spindles are formed, resulting in faulty segregation of chromosomes during cell division; nondiploid cells are produced, and development usually stops. Two mechanisms can operate to ensure that only one sperm fertilizes the egg.
To form identical or monozygotic twins, one fertilised egg (ovum) splits and develops into two babies with exactly the same genetic information. To form fraternal or dizygotic twins, two eggs (ova) are fertilised by two sperm and produce two genetically unique children.
However, for a given pregnancy, only the mother's genetics matter. Fraternal twins happen when two eggs are simultaneously fertilized instead of just one. A father's genes can't make a woman release two eggs.
It is estimated that 1 in 250 natural pregnancies will naturally result in twins. While twin pregnancies can happen by chance, there are some factors that may increase your odds of having two babies at the same time.
Hint: Generally, two sperms do not fertilize the same egg. When one sperm comes in contact with the zona pellucida layer, there occur changes in the membrane, which prevent further entry of sperms. Two sperm fertilizing the same is very rare and occurs in very rare cases and embryos usually do not survive.
Human eggs use chemical signals to attract sperm. New research from Stockholm University, Manchester University NHS Foundation Trust and The University of Manchester shows that eggs use these chemical signals to “choose” sperm. Different women's eggs attract different men's sperm – and not necessarily their partners..
It is true that identical twins share their DNA code with each other. This is because identical twins were formed from the exact same sperm and egg from their father and mother. (In contrast, fraternal twins are formed from two different sperm and two different eggs.)
Fertility is most likely if the semen discharged in a single ejaculation (ejaculate) contains at least 15 million sperm per milliliter. Too little sperm in an ejaculation might make it more difficult to get pregnant because there are fewer candidates available to fertilize the egg.
The concentration of sperm is what makes the semen cloudy and thick, so if your ejaculate is watery it is possible that you have a low sperm count. This doesn't mean you're infertile (so precautions to prevent pregnancy still need to be taken for couples that don't want to get pregnant).
"The first fraction of ejaculate is the most effective for conception." ScienceDaily. ScienceDaily, 26 May 2015. <www.sciencedaily.com/releases/2015/05/150526085347.htm>.
Research in genetics has shown that women with a mother or sister who had fraternal twins have a higher chance of having fraternal twins themselves. This is because the so-called “twin gene” that causes what is known as hyperovulation (when a woman to release two eggs at a time) is present in the family.
A little more than half of twin pregnancies end in preterm delivery (before 37 weeks). While 40 weeks is the full gestation period of the average pregnancy, most twin pregnancies are delivered at approximately 36 weeks (range 32-38 weeks depending on the type of twin pregnancy).
It's equally unsurprising that a Danish study found that twins are less likely to get married than non-twins. As twins have a partner from birth, the study suggests that they may not have the same desire for marriage as singletons.
They found that twins at first birth were linked to higher divorce rates at 13.7% compared to 12.7% for singletons. The link was statistically higher among moms attending college at 14.4% with twins vs. 10.5% with single births.
Recognizing a parent's face is one of the most important early skills babies learn. So when one of the parents has an identical twin, it's a recipe for confusion.
Several factors for causes of embryo splitting were suggested, including maternal age, prolonged embryo culture, ovarian stimulation, and zona pellucida (ZP) manipulation [6].