Patient education: When your baby is measuring large during pregnancy (The Basics)

How is a baby's growth measured during pregnancy? — This can be done in a few different ways.

Normally, pregnancy lasts about 40 weeks, counting from the first day of your last period. Doctors use the term "gestational age" to tell how far along the pregnancy is. For example, if you are 20 weeks pregnant, your baby's gestational age is 20 weeks. By knowing the gestational age, your doctor or midwife can estimate your "due date" and plan your care. It also helps them figure out if the baby is growing as expected.

Ways to check your baby's growth include:

●Ultrasound (figure 1) – This is an imaging test that creates pictures of the fetus (developing baby). An ultrasound is usually done early in pregnancy to help figure out the gestational age. Later in pregnancy, it is sometimes done to check how the baby is growing. The person who does the ultrasound can take measurements of specific parts of the baby's body. These usually include the head, belly, and femur (thigh bone).

●Feeling or measuring your belly – Your doctor or midwife can feel your belly from different angles. This helps them get an idea of the size of the fetus. They might also measure your belly, usually from the top of your uterus to your pubic bone (figure 2). Then, they can see how it grows over time.

These ways of measuring can give an estimate of your baby's size and weight. This can be compared with the average size and weight for babies of the same gestational age.

What does it mean if my baby is measuring large? — Doctors use the term "large for gestational age" when a fetus is measuring very big. This usually means larger than 90 percent of babies of the same gestational age.

Having a large baby is more likely if you:

●Are older than 35 years

●Have given birth before, especially if any of your other babies were large

●Were a large baby when you were born

●Are pregnant for longer than 40 weeks

●Are pregnant with a boy

●Have obesity or gained a lot of weight during pregnancy

●Have diabetes

●Have a fetus with certain genetic problems

Having a large baby increases the risk of some problems during or after birth. Many of these can be prevented or treated.

Will I need tests? — Yes. If your baby is measuring large during pregnancy, you will probably have more ultrasounds. These can be used to measure how the fetus grows over time. They also let your doctor or midwife measure your amniotic fluid and look at your placenta.

Will I need to have a cesarean birth? — It depends. If your baby is measuring very large during pregnancy, your doctor or midwife will talk to you about how to plan for the birth.

Sometimes, they need to do an "assisted" vaginal birth. This means using a tool called "forceps" or a special vacuum to help get the baby out.

In other cases, they might recommend a cesarean birth ("c-section"). This can prevent some of the problems that can happen when a very large baby is born vaginally. These include:

●Shoulder dystocia – This is when the baby's shoulder gets stuck behind the mother's pelvic bone as it moves down the vagina. This is serious because it can cause the baby to be injured or unable to breathe.

●Injury to the vagina or perineum – The perineum is the area between the opening of the vagina and the anus. The skin and muscles around your vagina and perineum can tear during vaginal birth.

●Postpartum hemorrhage – This is the medical term for heavy vaginal bleeding after birth.

A cesarean birth involves surgery. This comes with its own risks. Your doctor or midwife can talk to you about your situation and how best to plan for birth.

What happens after birth? — Babies born very large have a higher risk of problems after birth. These include:

●Breathing problems

●Low blood sugar

●High red blood cell count

When your baby is born:

●The medical team will be prepared to care for them and treat any problems. The baby might need close monitoring after birth.

●Once the baby has been checked over, you are encouraged to try breastfeeding right away. This can help keep your baby's blood sugar levels normal.

●Your baby will probably get blood tests soon after birth. These will check their blood sugar levels and sometimes their blood cell counts.

Will my baby have long-term problems? — It depends. Many babies that are born large have no long-term health problems. But they do have an increased risk of certain issues later in life, including:

●Obesity

●High blood sugar

●Heart problems

As your baby gets older, their doctor can check for these issues.

If your baby has a genetic problem, their doctor will talk to you about what to expect.

Is there anything I can do to help my baby grow normally? — Yes. In general, you can improve your chances of having a healthy pregnancy by going to all of your prenatal appointments. Follow your doctor's or midwife's instructions around taking care of yourself and your body.

To lower the risk of having a baby that is very large:

●If you have diabetes, it's important to keep your blood sugar under control. Ask your doctor if you are not sure how to do this.

●Try not to gain too much weight during pregnancy. Your doctor or midwife can talk to you about how much weight gain is ideal.

●If you have obesity, consider trying to lose some weight before you get pregnant. Your doctor or nurse can help you do this in a healthy way.

More on this topic

Patient education: When your baby is measuring small during pregnancy (The Basics)
Patient education: Abdominal ultrasound (The Basics)
Patient education: Cesarean birth (The Basics)
Patient education: Vaginal tearing during childbirth (The Basics)
Patient education: Labor and childbirth (The Basics)
Patient education: Gestational diabetes (The Basics)
Patient education: Prenatal care (The Basics)
Patient education: Nutrition before and during pregnancy (The Basics)

Patient education: C-section (cesarean delivery) (Beyond the Basics)
Patient education: Gestational diabetes (Beyond the Basics)
Patient education: Care during pregnancy for patients with type 1 or 2 diabetes (Beyond the Basics)