Average Birth Weight for Twins: What To Expect Week by Week

| Reviewed By Amanda Lundberg, BSN, RN

If you’re pregnant with twins, your babies will probably be born weighing less than singletons. Due to the possibility of growth restriction and the fact that many twins are born early, you can expect tinier babies when you’re having multiples.

How much can twins weigh at birth? While weights vary, twins usually weigh about 5 1/2 pounds at birth. Anything lower than 5 1/2 is considered low, so doctors hope each twin will arrive weighing at least this much. If your twins are born very early, they will weigh less and may need time in the neonatal intensive care unit (NICU).

Your doctor will estimate your babies’ weights throughout the pregnancy through ultrasounds and growth measurements. This will help you be prepared as you approach labor.

Twins Birth Weight

How much your twins will weigh when born depends on a variety of factors. What they weigh in the womb can help your doctor estimate what they will weigh at birth.

Average Birth Weight for Twins

The average birth weight for twins depends on what type of twins they are and if they are sharing a placenta. There are other factors that can affect birth weight as well.

Birth weight is important because babies born at a low birth weight are at risk for immediate and future complications.

  • Average Weight of Twins at 28 Weeks: Around 2 1/2 pounds
  • Average Weight of Twins at 30 Weeks: Around 3 pounds
  • Average Weight of Twins at 32 Weeks: Close to 4 pounds
  • Average Weight of Twins at 34 Weeks: Around 4 pounds 10 ounces
  • Average Weight of Twins at 35 Weeks: Almost 5 pounds
  • Average Weight of Twins at 36 Weeks: Slightly over 5 pounds
  • Average Weight of Twins at 38 Weeks: About 6 1/2 pounds

What Is a Healthy Weight for Twins at Birth?

A healthy weight for twins at birth is 5 1/2 pounds or more. That means each baby will weigh 5 1/2 pounds. Twins can be born weighing more than this, but at least 5 1/2 pounds is the goal.

How Early Can You Deliver Twins Safely?

You can deliver twins as early as 24 weeks, but there will be a long NICU stay for both babies if they are born this early and survive.

Most doctors want to wait until you are at least 34 weeks along before delivering twins. This isn’t always possible, but it gives their lungs longer to develop and their bodies more time to put on necessary weight.

Is 36 Weeks Full Term for Twins?

While 36 weeks can be considered full term for twins, most doctors try to wait until 37 weeks to deliver them.

Between 36 and 37 weeks is often considered a safe time depending on what type of twins you’re having and what is going on in the womb.

Can You Carry Twins to 40 Weeks?

It’s not advisable to carry twins to 40 weeks. The risk of stillbirth and other problems increases, and twins just don’t have the room to grow after around the 37 or 38-week mark.

Twins who are sharing a placenta do not need to be in the womb for a full 40 weeks.

Average Length of Twins at Birth

While average heights are difficult to find, most twins are born shorter than their singleton peers.

Does Birth Weight Predict Future Size?

Yes, birth weight can predict future size. Bigger babies tend to end up as bigger adults, and babies born at low birth weight babies often have lower body mass index as adults. 

Factors Affecting Birth Weight

Your babies sharing a womb will affect their birth weight, but there are other factors that impact birth weight as well.

1. Mom’s Health

If you struggle with certain health conditions, like anemia or high blood pressure, your babies are at risk of having a low birth weight.

Diabetes can actually cause your babies to put on too much weight in the womb and be born heavy. All of these conditions need to be managed well during pregnancy.

Of course, factors like poor nutrition, smoking, and drug use can negatively impact birth weight.

2. Gender

Boys often weigh more than girls at birth.

3. Age of the Mother

If you are less than 20 years old or more than 35 years old, you are more likely to have babies with a low birth weight.

Average NICU Stay for Twins

If you have twins, they could be in the NICU for any amount of time depending on when they were born. The average for twins is between 9 days and 25 days.

Babies Born at 8 Months Survival Rate

Babies born this far along in a pregnancy have an over 95 percent rate of survival.

Effects of Low Birth Weight

Low birth weight can affect a child’s mental and physical health later in life. It also affects their chances of survival throughout the first year of life.

However, many researchers warn against panicking about birth weight. The evidence for its effect is present but not fully understood.

Risks of Carrying Twins Past 38 Weeks

Carrying twins past 38 weeks can be risky, especially if they share a placenta. Even if they don’t, room in the womb runs out faster, and that leads to the possibility of complications.

After 38 weeks, the risk of stillbirth increases, and the benefits of staying in the womb aren’t significant.

Related Questions: 

What Is the Average Time Between Twins Being Born?

The average time between twins being born is around 17-19 minutes.

How Long Do Twins Stay in the Hospital?

If your twins are born without major medical issues or weight problems, they may go home within 3-4 days.

Twins who have to stay in the NICU average between 9-25 days depending on what medical problems they have and how much progress they are making.

Final Thoughts

Birth weight is important and will be monitored throughout your pregnancy, but don’t let it be a constant source of stress for you. Eat well, and follow doctor’s orders to ensure your babies get what they need in the womb.