Double-headed sperm are non-viable. They are unable to fertilize the egg and result in viable embryos. Thus, they are always dismissed in IVF cycles. When a sperm has two heads, the genetic material is also duplicated, which results in triploid embryos.
Usually, two sperm cannot fertilize the same egg. The reason behind this is that when one sperm comes in contact with zona pellucida then some changes occur in the membrane which prevents the further entry of sperms which is called polyspermy.
When the sperm has two heads, it is called a duplicate sperm, a condition linked to exposure to toxic chemicals, heavy metals like cesium, smoke or high prolactin hormone in the male. Large swollen midpiece or sperm neck may be related to defective mitochondria, the energy-making parts of the sperm cell.
Polyspermy is bad because, in addition to the extra set of chromosomes, a sea urchin sperm donates a centriole. The presence of additional centrioles during the first cell division will result in additional cleavage furrows and incorrect partitioning of the chromosomes (Fig. 7.21).
Pregnancies that result from polyspermy often result in spontaneous miscarriages during the second or third trimesters of pregnancy and fetuses that survive until childbirth are likely to not survive beyond a few days. Polyspermy can also complicate in vitro fertilization (IVF) by producing non-viable embryos.
Only two cases of human polyspermy leading to birth of children have been reported.
However, having a large percentage of misshapen sperm isn't uncommon. Typically, only around 4% to 10% of the sperm in a semen sample are normal, meaning that the vast majority don't look perfect under the microscope. Sperm morphology is poorly understood, and it can be subjective.
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.
The answer is no. The structure of the sperm does not affect the baby in terms of causing any defects physically or mentally. The only issue that can cause due to abnormal sperm morphology is that, depending upon the percentage and the density of abnormal sperms, the pregnancy can be delayed or not occur altogether.
Can an abnormally shaped sperm fertilize an egg? Yes, it can. However, having higher amounts of abnormally shaped sperm has been associated with infertility in some studies. Usually, higher numbers of abnormally shaped sperm are associated with other irregularities of the semen such as low sperm count or motility.
Several factors for causes of embryo splitting were suggested, including maternal age, prolonged embryo culture, ovarian stimulation, and zona pellucida (ZP) manipulation [6].
Here are the different types of multiple births: Superfecundation twins: When a woman has intercourse with two different men in a short period of time while ovulating, it's possible for both men to impregnate her separately. In this case, two different sperm impregnate two different eggs.
Sperm DNA can be damaged during sperm production and transport. This damage is known as DNA fragmentation. High levels of sperm DNA fragmentation have been shown to double the likelihood of a miscarriage occurring (Source – Men and Miscarriage Research).
Older paternal age may be harmful to the offspring's health in terms of genetic mutations, telomere length, and epigenetics [66]. Several lines of evidence suggest that epigenetic changes occur in the sperm of older fathers, particularly defects in DNA methylation [67–69].
Normal healthy sperm ranges in color from a transparent to a grayish white, while unhealthy sperm can often appear yellow-green or off-white. Additionally healthy sperm typically has a smooth oval shape, whereas unhealthy sperm may be curved or have abnormal shapes.
Early signs and symptoms include implantation bleeding or cramps, which can occur 5–6 days after the sperm fertilizes the egg. Other early symptoms include breast tenderness and mood changes.
Twins conceived from one egg and one sperm are called identical or 'monozygotic' (one-cell) twins.
How many sperm do you need to get pregnant? It takes just one sperm to fertilize a woman's egg. Keep in mind, though, for each sperm that reaches the egg, there are millions that don't. On average, each time men ejaculate they release nearly 100 million sperm.
There are many factors that can lead to the formation of sperm with an abnormal morphology. Genetic traits, exposure to toxic chemicals, increased testicular temperature and infection can cause abnormal sperm morphology. The most common cause is attributed to abnormal morphology (shape).
The head of the sperm contains the DNA, which when combined with the egg's DNA, will create a new individual. The tip of the sperm head is the portion called the acrosome, which enables the sperm to penetrate the egg.
Heteropaternal superfecundation is an extremely rare phenomenon that occurs when a second ova released during the same menstrual cycle is additionally fertilized by the sperm cells of a different man in separate sexual intercourse.
Conclusions. A single embryo transfer could produce different-sex twins.
A likely cause of the above scenario is polyspermy, in which one egg is fertilized by multiple sperm cells. In this case, the egg carrying the maternal DNA is shared between the twins, while the different sperm cells allow for segregation of paternal DNA such that the set given to each developing fetus is distinct.
Some research suggests that increasing body mass index (BMI) is linked with decreasing sperm count and sperm movement. Eat a healthy diet. Choose plenty of fruits and vegetables, which are rich in antioxidants — and might help improve sperm health. Prevent sexually transmitted infections (STIs).