Causes, consequences, prevention… Update on fetal macrosomia

Fetal macrosomia, a phenomenon that occurs during pregnancy, can pose risks for the expectant mother and the unborn child. What Causes Fetal Macrosomia? How to diagnose it? The explanations of Anh-Chi Ton, midwife in private practice.

Definition: What is fetal macrosomia? What are the symptoms ?

Fetal macrosomia is the fact that the fetus weighs an abnormally large amount in the womb: ” When measuring the child’s fetal growth, during various ultrasound examinations, doctors rely on percentiles, indicators for measuring the weight and height of the child. Example: A baby who is at the 50th percentile in weight at time T of pregnancy means that 50% of the other babies have a weight greater than or equal to that of the measured baby and that the other 50% have a have less or the same weight. A fetus is considered macrosome if its weight is above the 90th percentile. “, explains Anh-Chi Ton, midwife in private practice in Paris. In general, one speaks of a macrosome when its birth weight is over 4 kilos.

What causes macrosomia?

The causes of fetal macrosomia are diverse. However, the most common is gestational or even pre-gestational diabetes, which already exists before pregnancy. ” In gestational diabetes, the diabetic mother suffers hyperglycemia. That means the blood sugar level will be too high, explains the midwife. The fetus will then be in the same situation and produce high levels of insulin. It is this production that increases growth and fat in the fetus faster ».

In addition to gestational diabetes, other causes can lead to fetal macrosomia: The reasons for this phenomenon can also be genetic. Parents who are both tall are more likely to have a macrosomal baby. Women who already have at least one child are also more likely to be affected by this phenomenon. It may even be a human error: the baby is mistaken for macrosomal due to a conceptual error, due to the inaccuracy of the date of pregnancy onset ‘ explains Anh-Chi Ton.

Understand gestational diabetes

Gestational diabetes is a common phenomenon in pregnant women. In fact, with the imbalance in hormones, the rate of insulin secretion increases. This type of diabetes usually goes away after childbirth. Women who are overweight and obese or whose family members have diabetes have a higher risk factor. Gestational diabetes requires increased monitoring during pregnancy as it can lead to high blood pressure and even pre-eclampsia.

Screening: what are the signs of fetal macrosomia?

An examination of the pregnant woman’s uterus is essential to detect fetal macrosomia. Because during the perinatal examination, your gynecologist or midwife looks at the height of the uterus: if it is too high, you can assume that the unborn child will be a macrosome. An ultrasound is then performed to confirm the diagnosis.

Consequences: what are the risks of macrosomia? What to do at the beginning of childbirth

Fetal macrosomia is not trivial. Complications can occur in both the child and the mother.

The risks to the mother during the birth of a large baby

According to Anh-Chi Ton, the most important risk for the woman is the course of the birth: ” When giving birth to a macrosome baby, care must be taken to ensure optimal dilatation. Delivery in fetal macrosomia is not vaginal, but rather via cesarean section, episiotomy, or even forceps. An additional ultrasound is then performed after 36 weeks of amenorrhea. If the baby is really too big, we will proceed with labor induction ».

The risks for the child

There are many risks for babies, the main ones are a shoulder dystocia : The infant’s head is out, but its shoulders remain lodged in the mother’s pelvis. Shoulder dystocia can lead to sequelae, including nerve damage to the brachial plexus. It can also cause bone fractures or perinatal asphyxia.

The second most common risk is neonatal hypoglycemia. When macrosomia is related to gestational diabetes, the baby receives a large influx of sugar during pregnancy, which stops abruptly once the umbilical cord is clamped. The newborn, who will always have high levels of insulin, may then develop hypoglycemia at birth.

A phenomenon of breathing disorder can also occur in the context of diabetic fetal macrosomia. During pregnancy, the fetus’s lungs normally produce surfactant, a substance that helps develop lung maturity. When insulin levels are too high, the fetus produces less of it and is at risk of shortness of breath during labor.

There is no miracle cure for fetal macrosomia, but the risks can be reduced, the midwife assures: “ It is necessary for the pregnant woman to pay close attention to a balanced diet during her pregnancy, especially if gestational diabetes has been diagnosed. Physical activity is also recommended ».

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