Twice the Joy? The Truth About Delaying Pregnancy and the Chance of Twins

When you first see that positive symbol on your pregnancy test, there’s no way of knowing whether you’re expecting one baby or multiples. It’s just one of the many exciting yet slightly nerve-wracking aspects of pregnancy.

But the odds of conceiving twins have gone up over the past few decades. Reports from the National Center for Health Statistics (NCHS) found that in 1980, the twin birth rate was 18.1, or around 18 twin births for every 1,000 live births. In 2020, the twinning rate was 31.1, an almost 72% increase over four decades.

What could be increasing peoples’ chances of having twins? Experts suggest a few factors, such as an increase in fertility treatments, a rise in obesity, and the trend of delaying pregnancy until a person is older may be responsible for the twin trend. 

Do chances of twins increase with age?

There are two types of twins, identical twins (monozygotic) and fraternal twins (dizygotic). Identical twins come from a single egg and sperm that splits. These twins also share a placenta. Alternatively, fraternal twins come from two separate eggs and sperm and have their own placenta.

As you get older, the likelihood of conceiving twins increases. The higher rate of twin pregnancy with age is linked to hormones. Researchers have found that as women get older, they produce more follicle-stimulating hormone (FSH).

FSH is what encourages the ovaries to produce eggs. Usually, FSH stimulates follicle growth in one ovary. One follicle will mature enough to release a developed egg during ovulation that is able to be fertilized. However, in some cases, higher levels of FSH can cause more than one egg to be released. If more than one egg is fertilized, multiple babies are conceived, resulting in dizygotic, or fraternal, twins.

Usually, a rise in FSH levels begins around age 35 for those assigned female at birth. And it’s not just twins, you chance for any multiple pregnancy (twins, triplets, etc.) increases after age 35. This age is also when a pregnancy tends to be considered high-risk due to advanced maternal age.

What is considered advanced maternal age?

With the life expectancy for the average American woman reaching 79 years, as reported by the Centers for Disease Control and Prevention (CDC), 35 may not feel that old. But the American College of Obstetricians and Gynecologists (ACOG) has historically considered this age to be “advanced maternal age.” More definitively, a person assigned female at birth is considered of advanced maternal age if they will be 35 or older at the time of delivery.

Those who conceive at age 35 or older may also fall into the delayed pregnancy category.

…it’s not just twins, you chance for any multiple pregnancy (twins, triplets, etc.) increases after age 35.

What is delaying pregnancy?

Delayed pregnancy is a sort of catch-all term. Simply put, it means not having a child until later in life. Studies by the CDC have found that the age a person conceives their first child has increased from 21 in 1970 to 26 in 2020.

Many younger women are choosing to focus on their career or become more financially stable before having a child. Other women struggle with fertility issues or not find a partner they want to conceive with until they’re older. In either case, pregnancy is delayed. And, as we now know, delaying having a child into your thirties or even forties may make you more likely to conceive multiple babies during a single cycle.

Who is more likely to have twins?

There is a positive correlation between increased maternal age and twins. Still, older women aren’t the only group who may be more likely to get pregnant with more than one bundle of joy.

If you have been pregnant before, you have a slightly higher chance of having multiples with each subsequent pregnancy. Interestingly, this may be because you’ll be a bit older each time you conceive again. Patients with a family history of multiple pregnancies may also have an elevated risk of twins. A person is an estimated two times more likely to have twins if a close relative (like a parent or sibling) has had multiples. Individuals with a higher body mass index (BMI), often 30 or above, may also be more likely to become pregnant with more babies than they bargained for as well.

Finally, undergoing in vitro fertilization (IVF) or other fertility treatments significantly raises your odds of more than one baby per pregnancy.

What are the chances of twins in IVF?

Your chances of twins by age naturally increase due to hormones, but age may also play a role in your need for fertility treatment. The chances of twins in IVF are higher compared to unassisted conception.

When a woman turns 30, their fertility starts to decrease. Some individuals may know early on that they want to delay pregnancy and choose to preserve their fertility. Then, they can undergo IVF later in life when they feel ready to have a child. Other individuals may not delay pregnancy but turn to reproductive medicine due to infertility or needing an egg or sperm donor.

Though the likelihood of getting pregnant with multiples through IVF decreases as you age, IVF alone raises the incidence of twins, especially if an embryo transfer includes more than a single embryo. The resulting twin pregnancy is dizygotic, or fraternal, as two different eggs are fertilized. Chances of getting pregnant with identical twins through reproductive technologies are slimmer.

Regardless of the type of twin pregnancy, being pregnant with more than one baby at a time can pose risks.

Why are twin pregnancies high-risk?

Individuals pregnant with more than one baby are almost always considered to be at higher risk than those with singleton pregnancies. This designation is given because expecting multiples can increase your chances of obstetric and neonatal complications. High-risk pregnancy conditions in twin pregnancies can include:

• High blood pressure (preeclampsia)
• Gestational diabetes
• Congenital abnormalities
• Growth restriction
• Low birth weight
• Preterm birth
• Increased risk of cesarean section
• Increased risk of postpartum depression

That said, twin pregnancy risks don’t occur in every multiples pregnancy and being high risk doesn’t automatically mean you will experience issues.

Unfortunately, pregnancy at advanced maternal age can also come with risks. Therefore, pregnant people who are 35 or older are also usually considered high risk. Complications for pregnant women of advanced childbearing age and their unborn babies can include:

• Spontaneous miscarriage
• Hypertension
• Chromosomal abnormalities
• Prematurity (baby is born before 37 weeks gestational age)

These patients may also have increased risk of poor perinatal outcomes such as stillbirth or fetal death.

Fortunately, your obstetrics provider can offer advanced maternal age pregnancy guidelines, including ones adjusted for twin or multiple pregnancies, as well as prenatal care to help ensure the best possible pregnancy outcomes.

Considering pregnancy? Talk to Dr. Rad first!

Perinatologist Dr. Rad and his world-class Maternal-Fetal Medicine team at Los Angeles Fetal and Maternal Care Center understand your pregnancy and infertility needs before, during, and after birth. We provide compassionate care and help you understand your pregnancy, answer your questions, and provide the emotional support needed safely navigate your pregnancy.

We are currently accepting new patients. Call us at (844) 473-6100 or schedule your consultation online.

We are conveniently located for patients throughout Southern California and the Los Angeles area at locations in or near Beverly Hills, Santa Monica, West Los Angeles, West Hollywood, Culver City, Hollywood, Venice, Marina del Rey, Malibu, Manhattan Beach, Newport Beach, Irvine, and Downtown Los Angeles. We also offer in-home prenatal care and a fly-in program for out-of-town and international patients. Dr. Rad even travels to patients who need him throughout the U.S. and around the world.

If you can’t make it to Dr. Rad, he also offers virtual consultations worldwide.