Figuring out how to have twins starts with understanding how twins happen. Despite the amazing advances in computer imaging and genetic testing, how to have twins, in many respects, still remains a mystery. What we do know is that there are essentially three major things that happen when sperm meets egg and forms a zygote: The inner membrane gets filled with amniotic fluid, which eventually protects the fetus in the womb. The outermost protective membrane around the embryo becomes the chorion, which develops a supply of blood vessels.
And the chorion works with the uterus lining to form the placenta, which ultimately supplies oxygen and nutrients to the fetus, among other things. This zygote typically develops into a single embryo, which turns into a fetus and, eventually, your baby.
So, how to have twins? Twins happen when the situation veers a little offtrack from the above norm. Identical twins aka, monozygotic twins are the result of one egg being fertilized and then splitting into two embryos. Many experts believe this occurs as a result of some kind of cell abnormality, possibly resulting from a calcium deficiency that weakens the protein wall that holds the cell together.
Sure, indicators like shared eye and hair color, the same blood type, ear shape, even the order in which they cut their teeth can be indicative of identicals. However, developmental differences can happen in the womb, depending on where their umbilical cords implant—like how evenly they receive oxygen and nutrients from a shared placenta, for instance. This, in turn, can result in different heights and other features.
There are actually quite a few types of identical twins, but roughly two thirds of them are known as monochorionic-monoamniotic twins commonly referred to as mono-mono or MCMA twins. These twins have their own amniotic sacs in the womb but share the placenta and chorion. About another third are known as dichorionic-diamniotic identicals commonly referred to as di-di or DCDA twins.
While the vast majority of these twins occur when two eggs are fertilized by two sperm simultaneously see below , they can also originate from one sperm and one egg, which then form into a zygote that splits into two—giving each twin its own amniotic sac, chorion and placenta. Fraternal dizygotic twins happen when two eggs are being fertilized by two different sperm. They are simply siblings born at the same time.
All fraternal twins are di-di twins, meaning that they both have their own placenta, amniotic sac and chorionic sac. Except with rare scientific anomalies, boy-girl twins immediately tip you off that the twins are fraternal. Every mom of mixed-sex twins have a running joke about being asked if their twins are identical or fraternal. The same goes for same-sex twins who look dramatically different—like my daughters, who each have different hair and eye color.
How Common Are Twins? According to the Centers for Disease Control and Prevention's National Center for Health Statistics, the odds of having twins in the most recent figures available were With in vitro fertilization IVF , for instance, several eggs are extracted from the ovaries and brought together with sperm in the lab, in the hopes that at least one embryo will form; if more than one forms, then more than one is typically placed in the uterus to increase the chances of at least one implanting and turning into a healthy fetus.
Sometimes, though, more than one actually does—which explains why twinning rose a whopping 76 percent from to , as fertility treatments became more common. After removing the IVF factor, how common are identical twins? Not much at all.
The chances of having twins of this kind prove fairly consistent worldwide—around 4 for every 1, births. However, fraternal twin statistics vary all over the map, with the highest rate of dizygotic twinning found among the black populations of Africa: Girl twins are more common—which is the opposite case of singleton births in the US, where there are boys born for every girls. According to the Washington State Twin Registry, this is because the death rate for males in the womb is slightly higher, and when you factor in the increased chance of death in the womb for twins, a higher number of female survivors, and therefore female twins, result.
What Are the Chances of Having Twins? Your chances of having twins depends on a range of factors. You are about twice as likely as the general public to have twins if you, your mom or your maternal grandmother was a twin.
Now genetic studies are attempting to pinpoint which genes are responsible. One study boiled it down to two, and if a woman has both it increases her odds of having fraternal twins by 29 percent. One study found that 30 percent of twin dads had blood relatives who fathered twins. Other studies have found that dads with more robust sperm are more likely to have twins, regardless of family history. Even though twins run in my family, just plain being old is the real reason I think I was blessed with twins at age You are three times more likely to get pregnant with fraternal twins between the ages of 35 and 40 than between the ages of 20 and As you approach menopause, your body pumps out more FSH, a hormone that encourages the ovaries to release the last of their eggs—which can then result in releasing more than one egg.
Identical twinning appears to be color blind, but non-Hispanic black women have the highest chance of conceiving nonidentical multiples.
Hispanics and Asians are on the other end of the spectrum with Caucasians falling somewhere in the middle. In addition, a review study of 32 countries showed that the countries with taller women also revealed higher rates for twins.
Obese women those with a body mass index of 30 or higher typically have a tougher time conceiving, but when they do, they have higher chances of having twins than women with a healthier pre-pregnancy BMI of between 19 and However, research also suggests that women under pounds are three times as likely to conceive monozygotic twins, possibly due to low estrogen, which delays implantation and gives an egg more time to duplicate and split. One study found that women who were breastfeeding when they got pregnant had a much higher rate of conceiving twins—as in nine times more likely!
His studies also revealed that the longer women breastfeed, the higher the chance of having twins in future pregnancies, though the reason remains unclear. As a woman gives birth to more children, so do her chances of having twins.
For those who have already conceived fraternal twins spontaneously, brace yourself: Your odds of having twins again is quadrupled. According to the Washington State Twin Registry, the most fraternal twins are conceived in July and the least in January. Frederick Naftolin, professor of ob-gyn at New York University, suggests that it might be a byproduct of diet.
Various greens and the things that you eat that ingested those greens, such as the cow who supplied your beef and milk have different amounts of phytoestrogens, which can cause estrogen levels to rise or fall. This yam—a staple in Southwest Nigeria, the twin capital of the world—contains phytoestrogens that seem to enhance the release of more eggs, either directly or indirectly. Steinman found that fixed amounts of milk increased IGF levels in the blood, and vegans, who consume no animal products including dairy , had lower IGF than the general population.
Knowing that higher levels seemed to be a big factor in twinning in cows, he examined that the rate of twinning among vegans was less than half of the general population.
Cows injected with growth hormone in order to up milk and beef production have higher levels of IGF, he says, and in the US the rate of spontaneous twins has risen twice as much compared to countries where growth hormone injections are illegal. How to Have Twins Having a predisposition for a twin pregnancy is a scientifically valid phenomenon, but intentionally trying to improve your odds of conceiving twins?
Not a good idea, experts says. Alice Domar, MD, director of integrative care at Boston IVF, tells me she has a conversation every day with someone who says they want twins, often because they already have fertility issues and because IVF is expensive or because they are older and want an insta-family. But she urges them to look at the risks. This includes increased chances of gestational diabetes and pregnancy-induced hypertension. In addition, more than half of twin births in the US are preterm, notes the March of Dimes.
However, the smartest tips for how to have twins are those that simply enhance your fertility. Aside from keeping alcohol and caffeine to a minimum, maintaining a healthy weight, quitting smoking and not exercising to the extreme of messing up your menstrual cycle, Domar suggests taking a prenatal vitamin, and if you have an issue with egg quality, taking CoQ Several studies found as much as a 40 percent increase in twinning among women taking multivitamins with folic acid when they got pregnant.
How to get pregnant with twins or even with just one child as a result of having sex every which way has been a hot topic for centuries. For those undergoing IVF, a large study showed that women undergoing IVF who got acupuncture before their embryo transfers with good-quality embryos had a 42 percent pregnancy rate, while the control group had a 26 percent pregnancy rate. The 30 to 40 studies that followed, however, had mixed reviews as to whether the needles supplied more blood to the pelvis, decreased fertility-zapping stress or was even truly effective to begin with.
Next thing I knew, I was pregnant. If you happen to be monitoring your pregnancy early and closely as fertility patients do , blood tests—which end up revealing higher amounts of hCG, the pregnancy hormone—could also give an indication.
It just so happens that hCG is the hormone that brings on morning sickness, so women pregnant with twins may be more likely to experience nausea and fatigue. They may also show a little sooner than singleton pregnancies. Still, every pregnancy is such an individual experience, so there are no dependable clues that you have two babies on board—or more!