Twin Pregnancy Week by Week: What to Expect

I still remember sitting in the ultrasound room when the technician paused and said “there are two.”

Two.

I have been through it. This guide is what I wish someone had handed me on day one. We’ll walk through the weeks in groups rather than one at a time. It’s a more practical way to follow along, and honestly how most twin moms experience them anyway.

A note before we start: Every twin pregnancy is different. The type of twins you’re carrying, whether they share a placenta, and your own health history all affect your care. Use this as a starting point, not a substitute for your doctor’s guidance.

The quick version, if you want the big picture first:

• Twin pregnancies are monitored much more closely than singleton pregnancies
• Most twins are born between 36 and 38 weeks so your due date is a rough guide, not a target
• Symptoms are often more intense, especially in the first trimester
• Your care plan depends heavily on twin type (DiDi, MoDi, or MoMo)

First, how is a twin pregnancy different?

A twin pregnancy follows the same basic timeline as a singleton pregnancy. But almost everything about it is turned up a notch. Your body is growing two babies, which means higher hormone levels, more physical strain, and more frequent medical monitoring from start to finish.

A few things worth knowing from the beginning:

• Symptoms: Your symptoms will likely be more intense. Higher hCG levels mean more nausea, more fatigue, and a belly that shows up earlier than you expect.
• Appointments: You will see your doctor or midwife much more often than in a singleton pregnancy.
• Delivery: Most twin pregnancies deliver between 36 and 38 weeks, per standard obstetric guidelines. Your due date is more of a rough guide than a target.
• Twin type matters: Whether your twins are identical or fraternal, and whether they share a placenta or have their own, changes your entire care plan. Your provider will tell you this at your first ultrasound.

First Trimester: Weeks 4 to 13

What your babies are doing

It is genuinely incredible how much happens in these early weeks.

• Weeks 4 and 5: Each embryo is about the size of a poppy seed. Their hearts begin beating around week 5, and the neural tube that will become their brains and spinal cords starts forming.
• Weeks 6 to 8: Tiny arm and leg buds appear. Fingers and toes start developing. By week 8 they are officially called fetuses, not embryos.
• Weeks 9 to 11: Their faces become more defined. Fingernails begin to grow.
• Weeks 12 and 13: Bones start hardening. Each baby is about the size of a peapod. You are almost into your second trimester.

One of the moments that makes it feel real: hearing two heartbeats at your first ultrasound. Two distinct, separate beats. There is nothing quite like it.

What you are feeling

Here is the honest version: the first trimester with twins is rough for a lot of people. Because you are carrying two babies, your hCG levels tend to be higher than in a singleton pregnancy, and hCG is what drives those early symptoms.

• Nausea and vomiting that can be more severe and last longer. Some twin moms experience hyperemesis gravidarum, which is extreme nausea that needs medical treatment. If you cannot keep anything down, call your provider.
• Fatigue that is bone-deep. Your body is doing an enormous amount of work. Rest when you can, and let go of the guilt about it.
• Breast tenderness, bloating, and a bump that appears sooner than you expect.

If your symptoms feel extreme, say something. You are not being dramatic.

Prenatal appointments in the first trimester

• A confirmation ultrasound around weeks 6 to 9. This is where your provider will confirm how many embryos there are, check for heartbeats, and most importantly, determine how many placentas and amniotic sacs are present. That detail shapes everything about your care.
• A nuchal translucency scan between weeks 10 and 13, which screens for chromosomal concerns.
• First trimester blood work to check hormone levels and other markers.
• More frequent visits than in a singleton pregnancy. If your twins share a placenta, your provider may want to see you every two weeks even this early.

DiDi, MoDi, MoMo: what does it mean?
DiDi (dichorionic/diamniotic) twins each have their own placenta and amniotic sac. This is the most common type and carries the lowest risk. MoDi (monochorionic/diamniotic) twins share one placenta but have separate sacs. MoMo (monochorionic/monoamniotic) twins share both a placenta and a sac. This is the rarest type and requires the most monitoring. Your provider will identify your twin type at that first ultrasound.

First trimester priorities:

• Confirm twin type and placenta situation at your very first ultrasound
• If you haven’t already, start a prenatal vitamin with folate
• Find a provider experienced with twin pregnancies
• Rest as much as you possibly can and ignore the guilt

Second Trimester: Weeks 14 to 27

What your babies are doing

This is when things start to get real. Your babies go from looking like tiny aliens to looking like actual babies.

• Weeks 14 to 16: Their sex organs develop. Bones continue hardening. By around week 16 you may start feeling the first little flutters of movement, called quickening. With twins it can happen a bit earlier because there is less space.
• Weeks 17 to 20: Hearing develops and your babies may start responding to sounds, including your voice. Fingerprints form. A fine downy hair called lanugo covers their skin.
• Weeks 21 to 24: Fat begins accumulating under their skin. Lung development is picking up, which matters a lot if they arrive early. 24 weeks is generally considered the point of viability.
• Weeks 25 to 27: Their brains are developing quickly. They are more active and you will feel it. Eyes begin to open.

Somewhere in this trimester there will be a moment when you feel both of them moving at the same time. Two separate babies doing their own thing in there. It is strange and wonderful and genuinely hard to describe.

What you are feeling

The second trimester is often the most manageable stretch of a twin pregnancy. The worst of the nausea tends to ease, you have more energy, and you are not yet carrying so much weight that everything hurts. Enjoy it.

• You will show earlier and larger than singleton moms at the same stage. People will have a lot of opinions about your size. You are allowed to ignore all of them.
• Fetal movement increases week by week. With two babies moving around, it can feel like a lot going on in there.
• Back ache and round ligament pain as your uterus grows.
• Weight gain is actually really important this trimester. Aim for roughly 1 to 1.5 pounds per week. Your babies need it.

Prenatal appointments in the second trimester

• An anatomy scan between weeks 18 and 22. This is a detailed ultrasound checking each baby’s organs, growth, and development. Your provider will also confirm that both babies are growing at a similar rate.
• If you have MoDi twins who share a placenta, you will have ultrasounds every two weeks starting around week 16 to watch for Twin-to-Twin Transfusion Syndrome (TTTS). This is a condition that affects blood flow through the shared placenta and requires close monitoring. Read our full guide to TTTS here.
• For DiDi twins, ultrasounds are typically every four weeks through this trimester.
• Appointments every two weeks beginning around weeks 24 to 26.
• A glucose screening test around weeks 24 to 28. Gestational diabetes is more common with twins, so do not skip this one.

Second trimester priorities:

• Do not skip the anatomy scan it is one of the most important appointments of your pregnancy
• Stay on top of weight gain; it matters more than in a singleton pregnancy
• If you have MoDi twins, keep every single ultrasound appointment
• Enjoy this stretch. It really is the easiest part.

Third Trimester: Weeks 28 to Delivery

What your babies are doing

The third trimester is about growth and finishing touches. Both babies are putting on weight and their lungs are getting ready for the outside world.

• Weeks 28 to 31: Significant brain development. Lungs continue maturing. Each baby may be around two to three pounds by now.
• Weeks 32 to 34: Fat fills out under their skin, giving them that round newborn look. Lung development is nearly complete. Twins born in this window have very good outcomes in most cases.
• Weeks 35 to 37: Final weight gain. Most twins arrive somewhere in this range.
• Week 38 and beyond: Reaching 38 weeks with twins is genuinely something to feel good about. Per standard obstetric guidelines, this is considered full term for a twin pregnancy, and delivery is typically recommended at or before this point.

Somewhere around week 30 you will notice a shift. Not just bigger, but heavier in a way that is hard to explain. Everything takes more effort. That is normal. Your body is doing something remarkable.

What you are feeling

I will be straight with you. The third trimester with twins is physically hard. You are carrying significantly more than a singleton mom at the same stage, and there is not much space left for anything, including your lungs and your stomach.

• Pelvic pressure and difficulty walking. Two babies pressing down is not subtle.
• Shortness of breath because your uterus is pushing up against your diaphragm.
• Heartburn. There is simply no room for your stomach to do its job.
• Swelling in your feet, ankles, and hands. Some swelling is normal, but sudden or severe swelling warrants a call to your provider because it can signal preeclampsia.
• Braxton Hicks contractions are common, but learn to tell them apart from real preterm labor contractions.
• Sleep is hard. A pregnancy pillow helps more than you would think.

Prenatal appointments in the third trimester

• Weekly OB appointments from around 28 to 32 weeks through delivery.
• Ultrasounds every two weeks to check each baby’s growth, position, and fluid levels.
• Non-stress tests, often starting around 32 to 34 weeks, which monitor each baby’s heart rate and activity.
• Cervical length checks to assess preterm labor risk.
• Conversations with your provider about delivery method and timing. Have this discussion early in the third trimester, not at 36 weeks.

Know the signs of preterm labor. Over 60% of twin pregnancies deliver before 37 weeks. Call your provider right away if you have regular contractions (more than 4 to 6 per hour), pelvic pressure, lower back pain that comes and goes in a pattern, or a change in vaginal discharge before 37 weeks. Do not wait to see if it passes.

Third trimester priorities:

• Pack your hospital bag by 28 weeks (not 36, by 28)
• Know the signs of preterm labor and have your provider’s after-hours number saved
• Have your delivery conversation early; don’t let it sneak up on you
• Line up help for after the babies arrive, if you haven’t already

Prenatal appointment overview

This is a general guide. Your actual schedule will depend on your twin type and your provider. Twins sharing a placenta need significantly more monitoring than DiDi twins.

When will you actually deliver?

This is the question everyone asks. The short answer is: earlier than 40 weeks, almost certainly.

Here is a general guide based on twin type:

• DiDi twins (each with their own placenta and sac): typically around 38 weeks
• MoDi twins (shared placenta, separate sacs): typically 36 to 37 weeks
• MoMo twins (shared placenta and sac): often 32 to 34 weeks with intensive monitoring

About 60% of twin pregnancies deliver before 37 weeks. That does not mean something went wrong. It is just the nature of carrying two babies. Have your hospital bag packed by 28 weeks and know your route to the hospital.

Vaginal delivery or C-section?

It depends on how your babies are positioned, your health, their gestational age, and your care team’s assessment. A vaginal birth is possible and happens regularly when the lower twin is head down. C-sections are also common.

The best thing you can do is have this conversation with your provider well before you hit 36 weeks. Going into delivery with a clear plan, and a backup plan, makes the whole thing less stressful.

Complications worth knowing about

Twin pregnancies come with higher risks than singleton pregnancies. Knowing about them ahead of time does not mean something will go wrong. It means you will recognize warning signs and act on them.

• Preterm birth: The most common complication. Over 60% of twin pregnancies result in delivery before 37 weeks, per obstetric guidelines.
• Preeclampsia: A blood pressure disorder more common in twin pregnancies. Watch for severe headaches, vision changes, or sudden swelling and call your provider immediately.
• Gestational diabetes: More common with twins and manageable through diet and monitoring.
• Twin-to-Twin Transfusion Syndrome (TTTS): Affects MoDi twins when blood flow through the shared placenta becomes uneven. Your ultrasound schedule is designed to catch this early. Read our full guide to TTTS here.

Most twin pregnancies, even complicated ones, end with healthy babies. Your care team is watching closely for a reason.

You are going to be okay

Growing two people at once is a lot. Physically, emotionally, logistically. There will be weeks that feel manageable and weeks that do not.

But you will get through it. Take it one appointment, one week at a time. And one day you will be on the other side of it, telling another twin parent “I have been there” and meaning every word.

Keep going to your appointments. Ask all your questions. Be honest with your provider about how you are feeling.

If you are just getting started, our article So, you are expecting twins is a good next read and if you are still in the very early stages wondering whether you might be carrying multiples, start with the signs of a twin pregnancy.