Macrosomia Fetus (Big Baby)


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Evidence Based - Facts Checked

You might have heard parents happily boasting about how big their child was at birth. So, is it really something one should be glad about? The weight at birth has a significant role in understanding and predicting the child’s health in the future.

A newborn baby will have bodyweight in the range of 2.5 kg to 4.5 kg with 3.4 kg being the average1Shehzad, K. (2011, July). 'Neonatal birth-weights and reference intervals in sonographically monitored normal fetuses' Source.

Fetal macrosomia is a term used to describe a baby that grows bigger than usual inside the mother’s womb.

When is macrosomia a matter of serious concern? What are the possible risks associated? How can the condition be managed? This article aims at explaining all the vital facts about macrosomia that one should be aware of.


What Is Macrosomia?

Fetal macrosomia is a condition when the weight of the newborn is more than 4kg to 4½ kg or is higher than “90th percentile for a given gestational age2M;, B. S. (2003, May). 'Macrosomic births in the united states: Determinants, outcomes, and proposed grades of risk.' Source.

The first half of the word macrosomia is ‘macro’ which means large or big in Greek whereas ‘soma’ means body.

One reason for the baby to grow abnormally large in utero is attributed to an excess nutrient supply to the fetus.

Prevalence of Macrosomia Fetus - Big Baby?

The National Vital Statistics Report on births in the U.S. for 2015 records around 7% of newborns with a bodyweight of more than 4 kg, 1% weighed more than 4.5 kg, and a meager 0.1% of infants weighed more than 5 kg.

Hence, we can conclude that this condition is quite common.

What Can Cause Macrosomia Fetus (Big Baby)?

Macrosomia Causes

The causes of macrosomia are not quite definitive, and research till date has not been able to point out the exact reasons, however, there are a couple of risk factors associated with macrosomia, which are discussed below:-

- Gestational Diabetes or Overt Diabetes

Women who have gestational diabetes (i.e., the woman who develops diabetes during pregnancy) or have overt diabetes of either type I or type II have at least 15% -45% of the chances of giving birth to macrosomia babies3H;, K. K. (2015). 'Gestational diabetes mellitus and macrosomia: A literature review.' Source.

- Extremely Obese

Women who have a high BMI (body mass index) due to obesity are at a greater risk of macrosomia (big baby)4Gaudet, L., Ferraro, Z. M., Wen, S. W., & Walker, M. (2014, December 07). 'Maternal Obesity and Occurrence of Fetal Macrosomia: A Systematic Review and Meta-Analysis.' Source. It is quite normal for women to gain weight during pregnancy, but a weight gain of more than 16 kg can cause macrosomia. 

- History of Macrosomia

If the mother was born as a macrosomia fetus (big baby), it may cause the newborn to be macrosomia. Similarly, the woman who has already given birth to a macrosomia infant can have macrosomia fetus in the successive pregnancies5Akanmode, A. M. (2020, August 23). 'Macrosomia' Source.

- Postmature Babies

The risk of macrosomia is more when the pregnancy extends beyond 40 weeks because the process of accretion (deposition of nutrients in the fetus) occurs maximally in the third trimester. Therefore, the more time fetus spends inside the uterus, the greater is the risk of excess growth6Akanmode, A. M. (2020, August 23). 'Macrosomia' Source.

- Larger Volume of Amniotic Fluid

The larger the volume of the amniotic fluid the greater is the risk of macrosomia fetus7Hackmon R;Bornstein E;Ferber A;Horani J;O'Reilly Green CP;Divon MY;. (2007). 'Combined analysis with amniotic fluid index and estimated fetal weight for prediction of severe macrosomia at birth' Source.

- Gender

Male babies are heavier than female babies on average and hence, are at a greater risk of macrosomia8Lampl, M., Gotsch, F., Kusanovic, J. P., Gomez, R., Nien, J. K., Frongillo, E. A., & Romero, R. (2010). 'Sex differences in fetal growth responses to maternal height and weight.' Source

- Ethnic Origin

It has been found that Hispanic women are more prone to have fetal macrosomia than Asian, American, or African women9H;, Y. H. (2020, August). 'Fetal macrosomia in a Hispanic/Latinx predominant cohort and altered expressions of genes related to placental lipid transport and metabolism.' Source






What Are The Possible Complications Associated With Macrosomia Fetus (Big Baby)?


Complications in Mother Having Macrosomia Fetus (Big Baby)

There are a couple of problems that the mother may encounter during vaginal delivery in case of fetal macrosomia-

- Labor Induction

Unusually longer hours of labor and need of oxytocin for labor augmentation

- Maternal Injuries

Maternal Injuries like tearing of perineal muscles (muscles between the anus and the vagina) and vaginal tears may happen in case of macrosomia fetus

- Heavy Bleeding Post-Delivery

The uterus is supposed to contract once the baby comes out but in the case of a macrosomia fetus (big baby), the muscles may not contract in a similar manner leading to excessive bleeding10Gill, P. (2020, July 10). 'Uterine Atony.' Source.

- Uterine Tear

The risk of rupturing the uterus is more in women who have already undergone a C-section previously.

- Maternal Death

In rare cases, macrosomia can be the cause of the mother’s death due to severe complications11Said, A. S., & Manji, K. P. (2016, August 24). 'Risk factors and outcomes of fetal macrosomia in a tertiary centre in Tanzania: A case-control study.' Source

COMPLICATIONS IN Macrosomia Fetus

Following are a few issues the baby may face due to macrosomia:-

Complications During and Immediately Post Delivery in Macrosomia Fetus

 - Need for forceps delivery or vacuum pump for the delivery

- Fracture of baby’s bones like the clavicle during the delivery

- Lack of adequate oxygen supply to the baby

- The shoulder of the baby may get stuck under the mother’s pelvic bone

- Newborns may have low blood sugar levels

Complications Post Delivery as the Macrosomia Baby Turns into an Adult

Some children are at constant risk of developing metabolic syndrome. This disease is a combination of conditions like high blood sugar, high blood pressure, increased cholesterol levels, and abnormal accumulation of fat around the waist.


How Can One Identify Macrosomia

Accurate identification of macrosomia is possible only after the baby is born. The easiest way is by checking if the infant’s weight is more than 4 kg or not. However, your doctor may use a few other tests and techniques before delivery to rule out the risk of macrosomia fetus (big baby) such as:-

- Recording Medical History

Your doctor shall record your medical history. It will include the incidence of gestational diabetes or macrosomia baby in the previous pregnancy, if any, as these can help in predicting macrosomia in the current pregnancy.

- Recording the Fundal Height

The fundus’ height is equivalent to the distance between the pubic bone and the uterus’ topmost portion. If the fundal height is more than the expected values, one possible indication could be fetal macrosomia.

- Feeling the Abdomen

Another way of assessing the fetus’ size is by manual assessment and estimation, i.e., touching around the belly to know how big the baby is, however its not a highly reliable method.

- Ultrasonic Examination

This method is quite accurate and helps get a a rough estimation of the weight of the fetus at different times in the gestation.  These can be plotted on intra uterine growth charts to serially monitor the growth of the fetus.

- Levels of Amniotic Fluid

Excess amniotic fluid, medically termed as polyhydramnios, indicates an increase in urine production, which implies that the fetus is large.

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Can Macrosomia Be Prevented?

Macrosomia cannot be predicted accurately, and hence, there is no sure-shot way of preventing it. Nevertheless, there are a few steps that you can follow to limit the risk of developing fetal macrosomia.

- Control Blood Sugar Levels

Keeping a check on blood sugar levels is extremely significant, especially for those who are pre-diabetic or overtly diabetic or are suffering from gestational diabetes. High blood sugar puts the baby at risk of growing excessively in utero, thereby becoming a macrosomia fetus (big baby)(Pederson’s hypothesis).

- Dietary Modifications

It is recommended to adopt a diet rich in complex carbs and fiber content and low in saturated fats and cholesterol. Abstinence from all forms of refined sugars and junk food is ideal.

On the other hand, the inclusion of fruits, vegetables, sprouts, and lean proteins can help achieve satiety and curb the frequent hunger pangs and urge for snacking.

- Decrease Pre conception Weight

Those who are already on the heavier side should be more careful as they are more prone to gain excess weight during pregnancy. Ideally, pregnancy should be planned only if the pre conception weight is ideal for the height. You can approach an expert dietitian or your healthcare provider if you need help maintaining a healthy weight.

- Mild to Moderate Exercise

As diet alone may not suffice, finding at least half an hour to forty-five minutes for mild to moderate exercise five days per week is essential in maintaining body weight within a normal range. Walking and practicing yoga could be the best and most feasible form of exercise during pregnancy.

Quick Note - Before doing any exercise, consult your gynecologist.


How Can Macrosomia Be Managed?

If macrosomia is diagnosed during pregnancy, you should discuss the options of mode of delivery with your obstetrician; whether to opt for normal vaginal delivery or opt for C-section.

Normal Delivery With Macrosomia Fetus (Big Baby), Is It Possible?

It is challenging for mothers to push out a large baby through vagina as it may involve a lot of complications for both the mother and the baby.

Even if the mother is keen on going through normal childbirth, it needs to be done only under expert supervision in a hospital where the mother needs constant monitoring to conduct C-section promptly, should the needs arise.

An operative vaginal delivery may be opted for, that involves forceps or vacuum pumps to extract the baby from the womb; however, it has its own set of complications.

When is it Wise to Opt for C-Section Delivery if You Have a Macrosomia Fetus (Big Baby)?

  • You are diabetic and the baby’s weight is more than four and a half kilograms.
  • You are not a diabetic and the baby weighs more than five kilograms.
  • You had a previous delivery in which your baby had shoulder dystocia (when the shoulder of the baby gets jammed behind the pelvic bone of the mother)


Tests Done Post Delivery to Check the Health of the Macrosomia Baby

After the delivery, the baby will go through a series of examinations like:-

1. A physical exam to check if there are any birth injuries

2. Blood sugar tests to ensure if the baby has optimum blood sugar or not.

3. Blood cell count will be analyzed to rule out any blood disorders like polycythemia (an excess of red blood cells).

Tests Done Post Delivery to Check the Health of the Mother of Macrosomia Baby

After the delivery, the mother will go through a series of examinations like:-

1. The mother may need to undergo a blood glucose check-up to rule out any chances of  being diabetic

2. Examinations of the vaginal and perineal tear will be done and if any, your gynecologist shall devise a treatment regime for healing it


Conclusion

Macrosomia is when babies weigh abnormally more than their age. The cause of macrosomia is not clearly understood. The best way of minimizing the chances of developing macrosomia is by maintaining a healthy weight throughout pregnancy and keeping the blood sugar levels controlled if the mother has diabetes. Macrosomia fetus needs to be monitored as they grow into adults to prevent complications like diabetes or heart problems.


This content is medically reviewed by Dr. Nishant Mittal and written by Dr. Febin Mary George

Last Medical Review Date - 01st December 2020


References

  1. 1
    Shehzad, K. (2011, July).
    Neonatal birth-weights and reference intervals in sonographically monitored normal fetuses. Retrieved December 1, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3533353/
  2. 2
    Akanmode, A. M. (2020, August 23).
    Macrosomia.
    Retrieved December 1, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK557577/
  3. 3
    M;, B. S. (2003, May).
    Macrosomic births in the united states: Determinants, outcomes, and proposed grades of risk. Retrieved December 1, 2020, from https://pubmed.ncbi.nlm.nih.gov/12748514/
  4. 4
    H;, K. K. (2015).
    Gestational diabetes mellitus and macrosomia: A literature review.
    Retrieved December 1, 2020, from https://pubmed.ncbi.nlm.nih.gov/26045324/
  5. 5
    Gaudet, L., Ferraro, Z. M., Wen, S. W., & Walker, M. (2014, December 07).
    Maternal Obesity and Occurrence of Fetal Macrosomia: A Systematic Review and Meta-Analysis.
    Retrieved December 1, 2020, from https://www.hindawi.com/journals/bmri/2014/640291/
  6. 6
    Lampl, M., Gotsch, F., Kusanovic, J. P., Gomez, R., Nien, J. K., Frongillo, E. A., & Romero, R. (2010).
    Sex differences in fetal growth responses to maternal height and weight.
     Retrieved December 1, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3437780/
  7. 7
    H;, Y. H. (2020, August).
    Fetal macrosomia in a Hispanic/Latinx predominant cohort and altered expressions of genes related to placental lipid transport and metabolism.
    Retrieved December 1, 2020, from https://pubmed.ncbi.nlm.nih.gov/32494035/
  8. 8
    Hackmon R;Bornstein E;Ferber A;Horani J;O'Reilly Green CP;Divon MY;. (2007). 
    Combined analysis with amniotic fluid index and estimated fetal weight for prediction of severe macrosomia at birth. 
    Retrieved December 1, 2020, from https://pubmed.ncbi.nlm.nih.gov/17403410/
  9. 9
    Gill, P. (2020, July 10). 
    Uterine Atony. 
    Retrieved December 1, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK493238/
  10. 10
    Said, A. S., & Manji, K. P. (2016, August 24).
    Risk factors and outcomes of fetal macrosomia in a tertiary centre in Tanzania: A case-control study.
    Retrieved December 1, 2020, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4997651/

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This content is only for educational purpose and should not be considered as a substitute for your Physician's/Doctor's clinical judgement

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