Dreaming of double the newborn cuteness, but thinking it’s out of the realm of possibility? In reality, the idea of having twins may not be so far-fetched. (Just remember, it’s also double the diaper changes.)
But before you stock up on matching outfits and choose coordinating names, it’s important to understand how twins are conceived and the added factors involved. There are some circumstances — whether naturally occurring or gained through fertility treatments — that may make you more likely to have twins.
(Already expecting twins? Here’s what you need to know.)
It’s estimated that 1 in 250 pregnancies results in twins naturally, and there are two ways to conceive them.
The first involves a single egg being fertilized by a single sperm. Reproduction 101, right? But then, somewhere along the way, the fertilized egg divides into two, resulting in identical twins.
The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births. And while it may be obvious, identical twins are always the same sex, either both boys or both girls, at birth. Why? Well, they don’t just look alike — they also share the exact same DNA.
Fraternal twins, on the other hand, result when two separate eggs are fertilized by two separate sperm cells. Both fertilized eggs implant into the uterus and — nine months later — two babies are born.
Fraternal twins can either be two boys, two girls, or a boy and girl. They may or may not look a lot like. That’s because, unlike identical twins, they don’t share the exact same DNA. In fact, aside from age, they’re no more similar than brothers and sisters born years apart.
You may have heard that twins “run in families.” This is partially true. Your chances of having fraternal twins may be higher if you’re a fraternal twin yourself or if fraternal twins run on your mom’s side of the family.
One reason for this may be hyperovulation, which is a situation where the body releases two or more eggs during ovulation — basically a requirement for having fraternal twins.
And hyperovulation can be passed down in your DNA. (It can also happen once in a while in women who don’t regularly release more than one egg or have twins in their family, though.)
Are you over age 35? If you’re looking to have twins, you may hit the jackpot if you’re also in your upper 30s or in your 40s.
Women of “advanced maternal age” (we’re sorry to use the phrase, but it’s commonly used in medical settings to mean over age 35) have a higher chance chance of conceiving twins.
Hormonal changes that happen as you near menopause may encourage the body release more than one egg during ovulation. If two or more are fertilized and both implant, you might just need two cribs in your nursery.
Taller women seem to have a higher rate of having twins. This may sound a bit strange, but researchers credit a certain insulin-like growth factor with this possibility. A 2006 study uncovered that the rate of twins is higher in women who are more than an inch taller than the national average, which was 5 foot 3 3/4 inches at the time the study was published.
Women who are overweight also have a higher chance of conceiving twins naturally. Specifically, the chances are highest if your body mass index (BMI) is above 30.
On the flip side, BMIs that are under 18.5 show a reduced rate of having twins. The idea behind this theory goes back to the insulin-like growth factor and its influence on conception.
A word of warning here: Don’t intentionally gain weight to increase your chances of having twins. Having a BMI over 30 may also place you in the high-risk category of pregnancy, so talk to your doctor about a healthy weight for you before getting pregnant.
That said, Caucasian women over age 35 have the highest rate of higher order multiples, which means triplets or more.
Women who consume animal products, particularly dairy products, may be taking in extra insulin growth factor. The cows release this hormone into their milk and — when consumed — it may influence human reproduction.
Do you already have a child who’s looking to be a big brother or sister? He or she may be the reason you end up having twins. That’s right! Something called “high parity” — which basically means previous pregnancies — may increase your chances. They why isn’t entirely clear, but it may simply be because with each pregnancy, you’re a bit older.
And if you already have fraternal twins, you have a five times higher chance of having multiples again, according to the Twins and Multiples Birth Association in the United Kingdom (though we haven’t been able to confirm that statistic elsewhere). If it’s true, that’s quite a bonus round!
If you’re familiar with artificial reproductive technology (ART), in-vitro fertilization (IVF), and other fertility treatments — like in-utero insemination (IUI) — you may already know that twins are a heightened possibility.
While the procedure of IUI itself doesn’t increase your chances of having twins, certain drugs associated with it might. Clomiphene citrate (Clomid) and letrozole (Femara) are ovulation-stimulating medications.
Both of these drugs are often given in IUI cycles and may help the body produce multiple eggs that may release at the same time. If two (or more) are fertilized and implant, twins are a possibility.
And there’s more. Gonadotropins, like follicle stimulating hormone (FSH), stimulate the growth of egg follicles. These injectable medications are also often used in IUI and other fertility treatments, and the rate of twins while using these medications is a whopping 30 percent.
Drugs are also a part of IVF. But one of the main factors that increases your chances of twins with this reproductive technology is the number of embryos you decide to transfer. Some couples choose to transfer just one. While the single embryo might split and turn into identical twins, this isn’t too likely.
The more likely scenario is with regard to fraternal twins. If you transfer two (or more) embryos and they both successfully implant and develop, twins (or more!) are on the way.
The rate of twin pregnancies with IVF with fresh embryos is
And consider this: Some couples may choose to transfer two embryos during IVF. Say one of those embryos splits and then all three implant in the uterus. The result would be triplets — two identical twins and one fraternal sibling.
First things first: Before you start pinning cute twin nurseries on your Pinterest board, understand that twin pregnancies aren’t always fun and (baby shower) games. Being pregnant with multiples may carry certain complications and will automatically land you with a “high risk” classification with your doctor or midwife.
For example, twins are 12 times more likely than single babies to be born early. And they’re 16 times more likely to have a low birth weight. Not only that, but women carrying twins are also at an increased risk of developing preeclampsia and gestational diabetes.
All this isn’t to say you can’t have a totally healthy pregnancy with two babies. It just means you may need to be monitored a bit more closely.
Beyond the risks, a lot of the factors that increase the odds of having twins aren’t exactly in your control. So while you can choose to eat more dairy and yams, you can’t exactly change your height, race, or family history of multiple births. Purposefully gaining weight before pregnancy isn’t necessarily a good idea either.
And if you’re banking on having kids late in life to increase your odds of having twins, understand that with age comes reduced fertility and more chances of chromosomal abnormalities.
If you’re still stuck on the idea of two, reproductive technology may give you the most control. But experts currently recommend younger women transfer just
Ovulation-enhancing drugs used alone or with IUI require a prescription and may carry some serious risks, like higher chance of ovarian hyperstimulation or ectopic pregnancy.
Drugs and procedures like IVF are also costly and typically reserved for couples who have been diagnosed with infertility. For women under 35, infertility means not getting pregnant with timed intercourse in the course of a year. And for women over 35, this timeframe shortens to 6 months.
We’re not trying to be a Debbie Downer here. Talk to your doctor — particularly your reproductive endocrinologist if you’re doing fertility treatments — about twins. They can tell you about any associated risks unique to you and if doing a multiple-embryo transfer with IVF might be an option.
Unfortunately, there’s no special pill you can take that will guarantee you’ll be rolling a double stroller around your neighborhood like a boss. (But we think you’re a boss regardless.)
This isn’t to say you can’t have a little fun trying to increase your odds by dining on more cheese and sweet potato fries or crossing your fingers about your next IUI.
There are certainly both risks and rewards with twins. But before you get too carried away with dreaming, try first looking forward to seeing double… with the lines on your pregnancy test. We’re sending baby dust!