Macrosomia is the term used to refer to huge body size. When the fetus has a considerable excess of size, it is considered to have fetal macrosomia, a condition that is usually common in 6% to 10% of pregnancies and that represents a series of risks to the health of the newborn because it turns out that this belief of that the bigger the baby, the healthier it is, is not so confirmed.
Fortunately, it is possible to know and evaluate the baby’s weight before its birth, so it is possible to know about the fetal macrosomia ahead of time and offer the fetus the necessary care and supervision so that everything goes well on the day of birth and avoid future repercussions. In this FastlyHealarticle you can learn more about fetal macrosomia: causes, consequences, and treatment .
Table of Contents
When is a fetus considered to have fetal macrosomia?
Fetal macrosomia is the excessive size of the fetus. Fetuses usually have an average height and weight during the gestation period, similar to all pregnancies. However, both factors can increase or decrease, causing a variation. In the case of fetal macrosomia, some values allow determining when the growth of the fetus is considered excessive:
- Birth weight of 4,500 grams, or more than 4,000 grams, between 4.5 kg and 4 kg.
- The weight of the fetus at birth is greater than the 90th percentile. The percentiles refer to different aspects of children’s growth, such as height, weight, head circumference, and body fat, considering age, sex, and the mean. The doctor should examine children with a percentile below the 3rd or above 97.
Causes of fetal macrosomia
Many causes can intervene in pregnancy for a fetus to be macrosomic. Although the root cause cannot always be found, some of the reasons for fetal macrosomia include:
- By genetics . When both parents of the newborn are huge, the risk of the fetus being born with fetal macrosomia is higher. This genetic factor also increases the possibility of a more significant number of macrosomic fetuses in a family. It also increases the probability that a mother who has given birth to a macrosomic baby will have future pregnancies where the fetus presents fetal macrosomia.
- Maternal diabetes . Perhaps it is one of the most common causes of fetal macrosomia. Why? Because the elevated glucose levels that occur in people with diabetes also pass to the fetus, and there is an increase in fetal insulin. The problem is that insulin plays a fundamental role in the growth of fetuses, so when insulin increases, the fetus also increases its growth rate, which can cause fetal macrosomia. This cause is valid in cases of type 1 diabetes, type 2 diabetes, and gestational diabetes.
- Delayed delivery . A pregnancy should last between 37 and 40 weeks. When there is a delay in pregnancy, the fetus continues to grow and gain weight more than usual and may be born with fetal macrosomia. Pregnancy is quite delayed if there are no labor symptoms at week 42. Fortunately, today, when the pregnancy has reached the 40th week, and there are no contractions or breakage of the water, the specialists stimulate the baby’s birth, avoiding excessive growth and other complications.
- Obesity . Fetal macrosomia is closely related to the mother’s obesity. Although the cause is not known for sure, it is proven that pregnant women with obesity are at greater risk of having a macrosomic fetus. At the moment, it is believed that insulin resistance and hormonal disorders typical of obesity can influence the excessive growth of the fetus.
- Excessive weight gain of the mother during pregnancy. When the woman becomes pregnant, many metabolic, hormonal, and blood changes occur in her body, suggesting weight gain and necessary for a correct gestation process. However, it is about a progressive weight gain, from month to month, and never excessive or sudden. Although the reason is unknown, mothers who suddenly gain weight during pregnancy are at higher risk of developing a macrosomic fetus.
Impact of fetal macrosomia on the fetus
- Intellectual development of the fetus. Certain studies have attempted to link fetal macrosomia with the greater or lesser intellectual development of the fetus. Although there are specialists who say that it does affect intellectual capacity, nothing has yet been proven. Similarly, as we will see below, the risks are more important during and after pregnancy.
- Abortion or loss of fetal well-being. The chances of having an abortion increase if the fetus is macrosomic. But in addition, this risk factor is more common when the mother has diabetes because her condition can cause damage to the placenta, preventing it from providing the amounts of oxygen and nutrients that the fetus needs, which is known as loss of blood—fetal well-being. Also, the larger the fetus, the more oxygen, and nutrients it needs.
- Umbilical cord compression. At the same rate as the fetus grows, the mother’s uterus increases in size during pregnancy. In the case of fetal macrosomia, it may happen that at the end of pregnancy, the uterus has already reached its maximum stretch, and the fetus is still growing, leaving less space between the fetus and the uterus or causing compression of the umbilical cord. This can cause the fetus to stop receiving the necessary nutrients and oxygen.
Consequences of fetal macrosomia in the newborn
- Hypoglycemia . When the fetus is macrosomic due to maternal diabetes, its glucose and insulin levels are higher. At the time of birth, when the umbilical cord is cut and the maternal glucose supply is cut off, the newborn’s insulin levels remain elevated, and the blood glucose concentration falls. This process causes a sudden drop in blood sugar or hypoglycemia that can affect the newborn’s heart, kidneys, and even brain.
- Polycythemia . It is common for 50% of neonates with fetal macrosomia to be born with a high level of red blood cells, making the blood more viscous, altering the central nervous system, and increasing bilirubin levels.
- Hyperbilirubinemia. As we mentioned earlier, fetal macrosomia increases the risk of the newborn having high bilirubin levels due to the destruction of red blood cells that are in excess in the bloodstream. This must be controlled immediately because bilirubin can cross the cell barrier of the brain and nervous system, reaching and destroying neurons.
- Respiratory failure . When the fetus is macrosomic, the maturation of the lungs is slower, which is why the newborn can come into the world with a respiratory deficiency.
Impact of fetal macrosomia on delivery
- Traumatism. If childbirth is a complicated process, the delivery of a large fetus is even more so. As the maternal canals are not prepared to deliver such a large fetus, the baby may suffer trauma to the musculoskeletal structure, bruises to the head, or accidental or physician-stimulated clavicle fracture to help deliver the fetus naturally.
- Dystocias . It refers to all those situations that prevent delivery from being carried out vaginally, for example, when the shoulders prevent the fetus from leaving the vagina. In these cases, a cesarean section or a fractured clavicle of the fetus may be considered to expedite its exit.
- Perineal tear When the mother gives birth to a large fetus, she can suffer injuries or trauma to the vulva, leading to tears in the perineum. In the long term, after the delivery of a macrosomic fetus, the mother may experience urinary incontinence.
This article is merely informative, at FastlyHeal .com we do not have the power to prescribe medical treatments or make any type of diagnosis. We invite you to see a doctor in the case of presenting any type of condition or discomfort.
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I am a Surgeon with a diploma in comprehensive ultrasound and surgical care residency, an area I am specializing in. During the exercise of my profession, I have realized the need for patients to know the diseases they suffer, and I can tell you that a large part of their complications is due to a lack of information. Being a health web writer allows me to transmit my experience, without borders, to all those readers eager for knowledge, educate them in the prevention of diseases and promote a healthy lifestyle.