In rare cases, fraternal twins can be born from two different fathers in a phenomenon called heteropaternal superfecundation. Although uncommon, rare cases have been documented where a woman is pregnant by two different men at the same time.
This is an extremely rare occurrence in humans and is known as heteropaternal superfecundation. We don't know exactly how often this occurs and cases only arise when suspicious family members request DNA testing. But one study estimated that it might occur in as many as one in 400 (0.25%) twin births in the US.
It is possible for twins to have different fathers in a phenomenon called heteropaternal superfecundation, which occurs when two of a woman's eggs are fertilized by sperm from two different men.
Occasionally, two sperm are known to fertilize a single egg; this 'double fertilization' is thought to happen in about 1% of human conceptions. An embryo created this way doesn't usually survive, but a few cases are known to have made it — these children are chimaeras of cells with X and Y chromosomes.
Although this is quite rare it can happen and it's called superfetation. Two babies are conceived from separate acts in two different cycles. These babies can be from the same father or two different men. When heteropaternal superfecundation occurs, the babies are from different fathers.
A double pregnancy, or superfetation, is extremely rare — in fact, there aren't even stats on how often it happens — but it's scientifically possible. We're not saying you should worry about it happening to you, just that you can't say that it's impossible.
It's such a rare occurrence that medical experts have only been able to identify a few confirmed cases of superfetation in pregnant women. So, while yes, you could get pregnant while you're already pregnant, it's probably not something to worry about.
The gene versions that increase the chance of hyperovulation can be passed down from parent to child. This is why fraternal twins run in families. However, only women ovulate. So, the mother's genes control this and the fathers don't.
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.
Is there a third type? Traditionally, the science around twins has taught that identical and fraternal are the only two types. But a third type might exist, called polar body or half-identical twins.
Everyone has the same chance of having identical twins: about 1 in 250. Identical twins do not run in families. But there are some factors that make having non-identical twins more likely: non-identical twins are more common in some ethnic groups, with the highest rate among Nigerians and the lowest among Japanese.
According to the World Health Organization (WHO), the chance of conceiving from pre-cum is about 20% if you're using the withdrawal method. So, while it's low risk, it's not impossible.
If you have already had unprotected sex with another man, you may be worried his sperm might somehow affect your baby's looks or DNA. The good news is that this is impossible. Provided your partner is free from STIs, your baby will be perfectly safe, and not affected in any way.
The term “Irish twins” refers to one mother having two children who were born 12 months or less apart. It originated in the 1800s as a way to poke fun at Irish Catholic immigrant families who didn't have access to birth control.
The longest pregnancy ever recorded was 375 days long (17 months). In comparison most women are pregnant for 280 days.
You can get pregnant as little as 3 weeks after the birth of a baby, even if you're breastfeeding and your periods haven't started again. Unless you want to get pregnant again, it's important to use some kind of contraception every time you have sex after giving birth, including the first time.
There is no specific frequency with which a man should ejaculate. There is no solid evidence that failure to ejaculate causes health problems. However, ejaculating frequently can reduce the man's risk of getting prostate cancer. Ejacu-lation can be through having sex or masturbating a few times a day.
If your menstrual cycle lasts 28 days and your period arrives like clockwork, it's likely that you'll ovulate on day 14. That's halfway through your cycle. Your fertile window begins on day 10. You're more likely to get pregnant if you have sex at least every other day between days 10 and 14 of a 28-day cycle.
Women in their early 20s to early 30s have a one in four chance of becoming pregnant each month. However, the likelihood of becoming pregnant decreases as women continue to age past 30. In fact, women have only a 1 in 10 chance of becoming pregnant each month by the time they're 40.
Many people believe twins skip a generation, but that's just a myth. The idea that twins skip generations likely comes from the fact that the genetic factors contributing to twins only come from the gestational parent's side.
But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints. Like physical appearance and personality, fingerprints are largely shaped by a persons DNA and by a variety of environmental forces.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
Monoamniotic-monochorionic Twins
These types of twins share a chorion, placenta, and an amniotic sac. This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords.
One placenta and one amniotic sac.
This is the riskiest and rarest type of twin pregnancy. Fetal complications can arise due to tangling of the umbilical cords or an imbalance in nutrients, blood or other vital life supporting systems.
For the most part, twins and multiples share the same birthday. However, depending on the time of day the babies are born and how long the timespan is between each baby's birth, twins can be born on different days.