Multiple pregnancy usually happens when more than one egg is fertilized. It also can happen when one egg is fertilized and then splits into 2 or more embryos that grow into 2 or more babies. When one fertilized egg splits into 2, the babies are called identical twins.
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 sounds like fraternal twins do indeed run in your family!
The likelihood of conceiving twins is a complex trait, meaning that it is affected by multiple genetic and environmental factors, depending on the type of twins. The two types of twins are classified as monozygotic and dizygotic.
However, few genes appear to be definitively linked to hyperovulation, so it could just be that genetics in general on the mother's side contribute to the probability of having fraternal twins. Heredity on the father's side, on the other hand, does not increase a couple's odds of having twins.
If you're 30 or older, you're more likely than younger people to release more than one egg during a menstrual cycle. You have relatives who have had multiples. If you or other people in your family have had fraternal twins, you may be more likely to have twins, too.
You're 35 or older
As you age, your chance of conceiving twins increases. Researchers have found that women over 35 produce more follicle stimulating hormone (FSH) than younger women, which may cause more than one egg to drop at ovulation.
Early signs of a twin pregnancy include severe morning sickness, quick weight gain, and more breast tenderness. You may also notice an increased appetite or extreme fatigue. Plus, those who have a twin pregnancy may begin showing sooner.
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.
Luckily, most parents don't have to wait long to know for sure. "Today, twins can usually be diagnosed as early as six to seven weeks into the pregnancy," he says.
Identical twins are almost always the same sex, although there are some rare exceptions to this rule. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the same chromosomes (usually, XX for girls or XY for boys).
“Having twins is not twice as hard—it's exponentially more difficult,” says Natalie Diaz, author of What To Do When You're Having Two and CEO of Twiniversity, a global support network for parents of twins.
Superfetation is a phenomenon that occurs when a pregnant woman releases an egg, usually a few weeks into her pregnancy, and it's fertilized and implants in the uterus. The result is two separate pregnancies happening at the same time.
Several factors for causes of embryo splitting were suggested, including maternal age, prolonged embryo culture, ovarian stimulation, and zona pellucida (ZP) manipulation [6].
Twins or multiple births occur at a rate of about 2% in the population of 15,000 babies with Down syndrome recorded on the UK National Down Syndrome Cytogenetic Register . A total of 244 twin pairs are recorded (some prenatally diagnosed), including 29 pairs (11.8%) where both have Down syndrome.
Although certain factors increase the chance of having twins, there is no way to improve the odds of having twins naturally. A woman will usually find out that she is pregnant with twins from an ultrasound early on in the pregnancy.
No.
That's not all, Monga says. Women pregnant with twins complain of more back pain, sleeping difficulties, and heartburn than those who are carrying one child. Being pregnant with twins also carries a higher rate of maternal anemia and a higher rate of postpartum hemorrhage (bleeding) after delivery.
Monoamniotic-monochorionic Twins
This is the rarest type of twin, and it means a riskier pregnancy as the babies can get tangled in their own umbilical cords. If you have monoamniotic-monochorionic twins, your healthcare provider will monitor your pregnancy closely.
If two sperms fertilize an egg, things go wildly wrong, yielding a triploid offspring with 69 chromosomes with an extra set in addition to the normal maternal/paternal pair. An egg fertilized by three sperms receives two extra chromosome sets, resulting in a quadruploid individual with 92 chromosomes.
A twin pregnancy with two placentas and two amniotic sacs is the optimal twin pregnancy, as each baby has its own nutritional source and protective membrane.
Even if you are pregnant with twins, there's no guarantee you will produce hCG any sooner than if you were pregnant with one baby. But because your levels may be higher, it is possible to detect a pregnancy slightly earlier due to higher levels of hCG.
The notion that twins always skip a generation is also a myth. The illusion may have arisen because men who inherit the gene from their mothers are unaffected by it ( they do not ovulate), but can still pass it on to their daughters, who, in turn, will have an increased likelihood of conceiving twins.