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Help, the baby is huge! What should you do when the baby is large for gestational age?

large for gestational age

We can establish that it is crucial to detect children who are not growing as they should intrauterine. A question that arises then is, of course, what do we do with children who are growing too much?

This week's blog post is a continuation of the previous posts about the examinations we offer women during pregnancy and about fetal size. It also touches on the topic of excessive or insufficient amniotic fluid.

It is common at our clinic for women to come to me after an ultrasound examination and look almost panicked. They often say, "They said my baby is huge! What do I do now? I absolutely can't deliver such a big baby; I need a cesarean section."

Large for Gestational Age (LGA)

Definition of LGA

Here it is interesting because we use different definitions depending on where in the world the child is born.

Large for Gestational Age (LGA) is used to describe newborns who weigh more than usual in correlation to their age (number of gestational weeks).

Infants can be considered large for gestational age if they weigh more than 9 out of 10 children (90th percentile) or more than 97 out of 100 children (97th percentile) at the same gestational age.

Definition in Sweden

They are among the approximately 3% largest children for their gestational age (+2 standard deviations or approximately the 97th percentile).

Sometimes the term "Macrosomia" is also used, which means a Fetal Weight ≥ 4500 g, regardless of gestational age.


Why is this a significant issue?

Because we know that macrosomia is associated with an increased incidence of complications for both the woman and the baby during pregnancy and childbirth.

A few years ago, we received strict instructions to "turn a blind eye" to large babies. Essentially, to pretend as if nothing was wrong because we didn't really know what to do with them.

Even though both we and the women knew there were risks. Today we handle this large patient group a little differently.

In the late stages of pregnancy, the fetal weight increases by an average of 200 g per week. If the child has accelerated growth, it means that the child is growing at a rate that exceeds the average increase.

The rule is that accelerated growth should be confirmed with two ultrasound measurements taken two to four weeks apart because we know that the examination of large babies has relatively low accuracy.

So we know that the margin of error in weight estimation is +/- 8%. The knowledge says that it is more difficult to measure large babies, meaning the margin of error can be larger.

That means the child can be smaller than the indicated value, but it can also be larger. Much larger.

How do we think today?

The first thing we think when we encounter a woman with a large baby in her belly is diabetes.

We usually know about type 1 diabetics beforehand, but today gestational diabetes mellitus (GDM) is becoming increasingly common.

GDM is a common condition during pregnancy, and it involves increased blood sugar levels in the mother but only during pregnancy. This increases the risks for both the woman and her baby during pregnancy and childbirth. One of the risks is having a large baby.

A large Swedish multicenter study on GDM was conducted, studying the neonatal outcomes of GDM pregnancies between 1991 and 2003 in Sweden.

The study was published and had a significant impact on the care of women with GDM. The threshold for acceptable blood sugar levels was lowered, resulting in a significantly increased number of women being diagnosed with the condition.

At Södersjukhuset in Stockholm, approximately 7,500 babies are born each year. In 2020, the guidelines for GDM.

In 2016, 46 of the pregnant women who gave birth at SÖS were diagnosed with GDM (gestational diabetes mellitus).

In 2021, the number has increased to 553.

This means that approximately 12 times as many women are now being diagnosed with GDM compared to 2016.

The question is whether the outcome has improved or worsened.

I don't have the answer yet.

During the autumn, a student project will be conducted at the clinic to study the outcomes for women and children with GDM at Södersjukhuset. So, more information will follow!

large for gestational age - ultra sound

What do we do in practice?

As mentioned, we follow up with another ultrasound because the margin of error is significant. The OGTT (oral glucose tolerance test) should be performed to rule out diabetes.

In short, this means that the woman is given a sugar solution, and her blood sugar is measured before the drink and several times in the hours after she has consumed the drink.

Most pregnant women find this super unpleasant, and many vomit up the drink, so the analyses are not always optimal.

If the estimated birth weight is ≥ 4500 g, individual considerations should be taken into account regarding the woman's ability to give birth, such as:

  • Previous deliveries

  • The woman's physical conditions (height)

  • Preferences regarding the initiation and method of delivery

  • Plans for future pregnancies

We often try to induce labor early in these cases. Delivering the baby around two weeks early (at 38+0 weeks) prevents further growth.

During the 41-week ultrasound, if the abdominal diameter (MAD) is ≥ 128 mm, the baby's weight is estimated. This means that if a large abdominal diameter is measured at the 41-week ultrasound, a complete weight estimation should be performed.

Knowledge suggests that these babies (MAD ≥ 128 mm) have an increased risk of expected birth weight ≥ 5000 g at 42+0 weeks.

These women should also be referred to specialized maternity care for discussions and decisions regarding the initiation and method of delivery.

How do we approach the delivery?

In plain terms, this is a high-risk delivery, which is known to everyone working in the delivery department.

We know that even if the fetus appears large and strong, these babies are more fragile than those with normal weight. They tolerate periods of oxygen deprivation shorter than their normal-weight counterparts.

We are also concerned about shoulder dystocia, which means that the fetus gets stuck during delivery.

We must always be prepared, and we try to do everything possible to avoid this. However, a number of shoulder dystocia cases still occur at SÖS every year.

Not all of these cases involve large-for-gestational-age (LGA) babies, but some do.

These are our current guidelines:

  • For expected fetal weight ≥ 5000 g, consider cesarean section.

  • For diabetes and expected fetal weight ≥ 4500 g, consider cesarean section. Why? Because these babies often have abnormally wide shoulders and an even greater chance of getting stuck during birth.

  • For expected fetal weight ≥ 4500 g, make an individual decision regarding continued management and birth planning.

too much or too little amniotic fluid

Sometimes, a woman may come in with an ultrasound showing excessive amniotic fluid, which is medically referred to as polyhydramnios. Sometimes, the fetus is large as well, but not always. What do we do in such cases?


Amniotic fluid, or the fluid surrounding the unborn fetus, protects and maintains a stable temperature for the fetus. Amniotic fluid is approximately 98% water with a neutral or slightly alkaline pH.

Polyhydramnios means there is too much amniotic fluid, according to certain definitions (>2 liters).

In the early stages of pregnancy, amniotic fluid is clear but becomes increasingly cloudy due to sebum, skin secretions, shed skin cells, and fetal hair strands. Meconium, the fetal stool, may also be present in the amniotic fluid, especially if the fetus is experiencing intrauterine stress.

Polyhydramnios is more common in the later stages of pregnancy. The amniotic fluid volume is highest around weeks 34-38, typically ranging from 400-1200 ml.

The diagnosis of polyhydramnios is made through ultrasound examination, where different "pockets" of amniotic fluid are measured.

Why could you get excessive amniotic fluid?

Common causes of excessive amniotic fluid include:

  1. Twin pregnancy

  2. Diabetes in the mother, including gestational diabetes (GDM)

  3. An obstruction in the baby's gastrointestinal tract (atresia)

  4. Various types of infections in the mother during pregnancy

  5. Immunization issues related to different blood types

Excessive amniotic fluid can be due to maternal conditions, such as diabetes, or fetal abnormalities, such as problems in the fetal gastrointestinal tract.

Neurological, skeletal, and muscular issues in the fetus can also lead to reduced swallowing ability and increased amniotic fluid.

The same occurs in chromosomal abnormalities such as trisomy 21 and 18, where polyhydramnios is more common.

What do we do if a woman has excessive amniotic fluid?

Ultrasound is usually where the diagnosis is made. We recommend further testing, such as a glucose tolerance test (to exclude diabetes in the mother).

We also conduct TORCH tests.

TORCH tests involve screening the woman for:

  • Toxoplasma

  • Rubella virus

  • Cytomegalovirus (CMV)

  • Herpes simplex virus types 1 and 2

  • Parvovirus B19

All these viral infections during pregnancy are associated with excessive amniotic fluid. However, in many cases, the cause remains unknown.

reasons for too much amniotic fluid
Image by storyset on Freepik

Vilka symtom har polyhydramnios?

Symptoms of polyhydramnios: A large amount of amniotic fluid often leads to a distended uterus and an increased risk of premature labor.

Excessive amniotic fluid also allows more space for fetal movement, which can result in the baby not engaging. The most common reason for seeking medical attention is discomfort and difficulty sleeping and eating.

Depending on the amount of excess fluid, we handle these cases differently. In mild cases, where symptoms are relatively mild, we simply monitor the fluid volume with ultrasound every two to three weeks.

In cases where the situation becomes unbearable due to excessive amniotic fluid, we consider inducing labor.

Naturally, the decision depends on the gestational week. In full-term pregnancies, we sometimes choose to induce labor for the mother's well-being.

Of course, there are also conditions with too little amniotic fluid, known as oligohydramnios.


Oligohydramnios refers to an insufficient amount of amniotic fluid. One reason for this can be abnormal development of the fetal kidneys or an issue preventing urine from leaving the fetal bladder.

Insufficient amniotic fluid is usually detected or confirmed through ultrasound.

Often, the mother may not notice it herself; it is discovered during an ultrasound examination. In cases of oligohydramnios, the fetus may require intensive monitoring until delivery.

Experiencing too little amniotic fluid is very rare.

Towards the end of pregnancy, amniotic fluid naturally decreases. It is not uncommon for oligohydramnios to be detected during the 41+0 week ultrasound.

In such cases, induction is usually recommended.

As always, it's not that simple!

We continually monitor and strive to do our best.

/Doctor Eva


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