Pregnancy

Twin Pregnancy: What to Expect, Types of Twins and Extra Monitoring

By the Find Her Doctor editorial team · Updated November 1, 2026 · 5 min read

A twin pregnancy usually means more prenatal visits, more ultrasounds, and a closer watch for complications like preterm birth, preeclampsia and gestational diabetes. How closely you're monitored depends mostly on whether your twins share a placenta, which an early ultrasound can show. Most twin pregnancies are co-managed with, or at least checked by, a maternal-fetal medicine (MFM) specialist.

Most people find out the same way: lying on the ultrasound table, the tech goes quiet for a second, then turns the screen. Shock, laughter, tears, sometimes all three. Once that settles, the single most useful question you can ask is: "Do they share a placenta?"

How twins are found

Usually on a first-trimester ultrasound. Some people notice stronger nausea, more exhaustion or a belly that grows faster than expected, but those signs vary so much they can't confirm anything. Higher hCG levels can hint at twins but aren't reliable alone.

The type of twins that matters for your care

Fraternal twins come from two eggs fertilized by two sperm. Identical twins come from one fertilized egg that splits. For your care, what matters more is how the placentas and sacs are arranged, called "chorionicity":

The type is easiest to see on ultrasound in the first trimester, so an early scan matters. If nobody has told you which type you have, ask, and write it down.

What makes twins more likely?

• Fertility treatment, including IVF with more than one embryo and ovulation-inducing medicines
• Being older, especially over 35
• A family history of fraternal twins on the mother's side
• Several previous pregnancies

The risks, plainly

Twin pregnancies have higher chances of:

• Preterm birth: more than half of twins are born before 37 weeks
• Preeclampsia and high blood pressure: carrying twins is a high-risk factor; see our preeclampsia guide
• Gestational diabetes
• Growth problems: one or both babies growing slowly, or a big size difference between them
• More severe nausea, including hyperemesis gravidarum
• C-section delivery

Shared-placenta complications

When twins share a placenta, the blood vessels can connect unevenly. That can cause:

• Twin-twin transfusion syndrome (TTTS): one twin gets too much blood flow and the other too little
• Selective growth restriction: one twin gets a smaller share of the placenta
• Twin anemia-polycythemia sequence (TAPS): an imbalance in red blood cells between the twins

This is why mono-di twins get ultrasounds so often. Caught early, TTTS can often be treated, sometimes with laser surgery on the placenta at specialized fetal centers. The every-two-weeks scans feel relentless, but they're the safety net.

Your prenatal care, month by month

Compared with a single-baby pregnancy, expect:

• First trimester: an early ultrasound to determine chorionicity, and a referral or consult with a maternal-fetal medicine specialist
• Genetic screening: cell-free DNA can be done in twins, though it's less studied than in single pregnancies. See our NIPT guide.
• Around 18 to 22 weeks: a detailed anatomy scan for each baby, often with a fetal heart scan for monochorionic twins. Plan for a long appointment.
• Growth ultrasounds: often every 4 weeks for di-di twins, more often for mono-di
• Cervical length checks in some practices
• Low-dose aspirin to lower preeclampsia risk, if your provider recommends it

Bed rest isn't recommended to prevent preterm birth in twins. It hasn't been shown to work and carries its own risks, like blood clots and muscle loss.

A practical tip: with this many appointments, ask whether your ultrasounds and OB visits can be booked back to back on the same day, at the same site. It can save you a lot of trips.

Weight gain with twins

The National Academy of Medicine (formerly the Institute of Medicine) suggests:

There isn't enough data to set a range for people who were underweight. Your provider or a dietitian can help. Late in pregnancy, when there's barely room for your stomach, small frequent meals work better than three big ones.

What it actually feels like

Most pregnancy symptoms come earlier and stronger with twins. You may:

• Show sooner and measure bigger at every visit
• Feel wiped out, especially in the first and third trimesters
• Have more heartburn, back pain, swelling and shortness of breath as the uterus grows
• Feel kicks from two babies, sometimes on opposite sides
• Struggle to sleep comfortably later on

Don't brush off a worrying symptom as "just twins." Call.

When twins are usually delivered

ACOG's general timing for uncomplicated twins:

• Di-di twins: around 38 weeks
• Mono-di twins: between 34 and 37 weeks
• Mono-mono twins: between 32 and 34 weeks, usually by C-section

Complications can change this. Whether a vaginal birth is an option depends mostly on the position of the first twin (the one closest to the cervix) and other factors; your provider will go through it with you.

Getting ready, earlier than you think

Because twins often arrive early:

• Tour your delivery hospital and ask about its NICU level, since a NICU stay is more common with twins
• Plan work leave earlier, in case you need to stop before your due date
• Talk with a lactation consultant during pregnancy about feeding two
• Line up help at home for the first weeks
• Pack your hospital bag by the early third trimester (around 28 weeks is not too soon)

Twin care in New York

Mono-di and mono-mono twins, and twins with complications, are often followed at hospitals with MFM services and a high-level NICU. New York designates certain hospitals as Regional Perinatal Centers, the highest level in the state's perinatal system; see delivering at a Regional Perinatal Center. Fetal therapy for TTTS is available only at specialized centers, and your MFM team will refer you if needed.

If you're uninsured, NY Medicaid covers pregnant people with incomes up to 223% of the federal poverty level. Search the directory to find OB/GYNs and MFM specialists near you.

When to call your provider

Call right away if you have:

• Regular tightening, cramping or contractions, or pelvic pressure, before 37 weeks
• A dull low backache that comes and goes
• Leaking fluid or a change in discharge
• Vaginal bleeding
• Sudden rapid growth of your belly, tightness, or shortness of breath (possible signs of fluid imbalance in mono-di twins)
• A severe headache, vision changes, upper belly pain or sudden swelling
• Fewer movements from either baby than usual

Call 911 for heavy bleeding, severe pain, chest pain or trouble breathing.

Frequently asked questions

Sources

• ACOG — Multifetal Gestations: Twin, Triplet, and Higher-Order Multifetal Pregnancies (Practice Bulletin 231)
• ACOG — Medically Indicated Late-Preterm and Early-Term Deliveries (Committee Opinion 831)
• Society for Maternal-Fetal Medicine — Twin-Twin Transfusion Syndrome (Clinical Guideline)
• Institute of Medicine (National Academy of Medicine) — Weight Gain During Pregnancy: Reexamining the Guidelines
• ACOG — Multiple Pregnancy FAQ

This article is for general education and is not medical advice. It does not replace an evaluation by a licensed clinician who knows your history. If you think you have a medical emergency, call 911.