Large for gestational age

Fetal macrosomia and LGA often do not present with noticeable patient symptoms. Important signs include large fundal height (uterus size) and excessive amniotic fluid (polyhydramnios). Fundal height can be measured from the top of the uterus to the pubic bone and indicates that the newborn is likely large in volume. Excessive amniotic fluid indicates that the fetus's urine output is larger than expected, indicating a larger baby than normal; some symptoms of excessive amniotic fluid include • shortness of breath • swelling of lower extremities & abdominal wall • uterine discomfort or contractions • fetal malposition, such as breech presentation. Infant complications Common risks in LGA babies include shoulder dystocia, metatarsus adductus, hip subluxation and talipes calcaneovalgus, due to intrauterine deformation. Newborns with shoulder dystocia are at risk of temporary or permanent nerve damage to the baby's arm, or other injuries such as fracture. Both increased birth weight and diabetes in the gestational parent are independent risk factors seen to increase risk of shoulder dystocia. In diabetic women, shoulder dystocia happens 2.2% of the time in babies that weigh less than , 13.9% of the time in babies that weigh to , and 52.5% of the time in babies that weigh more than . LGA babies are at higher risk of low blood sugar (hypoglycemia) in the neonatal period, independent of whether the mother has diabetes. Hypoglycemia, as well as hyperbilirubinemia and polycythemia, occurs as a result of hyperinsulinemia in the fetus. High birth weight may also impact the baby in the long term, as studies have shown associations with increased risk of overweight, obesity, and type 2 diabetes mellitus. Studies have shown that the long-term overweight risk is doubled when the birth weight is greater than 4,000 g. The risk of type 2 diabetes mellitus as an adult is 19% higher in babies weighing more than 4,500 g at birth compared to those with birth weights between 4,000 g and 4,500 g. Pregnant mother complications Complications of the pregnant mother include: emergency cesarean section, postpartum hemorrhage, and obstetric anal sphincter injury. Compared to pregnancies without macrosomia, pregnant women giving birth to newborns weighing between 4,000 grams and 4,500 grams are at twice the risk of complications, and those giving birth to infants over 4,500 grams are at three times greater risk. == Causes ==

Multiple factors have been shown to increase the likelihood of infant macrosomia, including preexisting obesity, diabetes, or dyslipidemia of the mother, gestational diabetes, post-term pregnancy, prior history of a macrosomic birth, genetics, and other factors. The risk of having a macrosomic fetus is three times greater in mothers with diabetes than those without diabetes. Obesity in the mother Obesity before pregnancy and maternal weight gain above recommended guidelines during pregnancy are other key risk factors for macrosomia or LGA infants. It has been demonstrated that while maternal obesity and gestational diabetes are independent risk factors for LGA and macrosomia, they can act synergistically, with even higher risk of macrosomia when both are present. Genetic disorders of overgrowth (e.g. Beckwith–Wiedemann syndrome, Sotos syndrome, Perlman syndrome, Simpson-Golabi-Behmel syndrome) are often characterized by macrosomia. Other risk factors • Gestational age: pregnancies that go beyond 40 weeks increase the incidence of an LGA infant • Maternal gut microbiome: A correlation has been identified between the maternal gut microbiome and macrosomia in recent research. The occurrence of macrosomia may be influenced by specific gut microbiota, including Bacteroides salyersiae, Bacteroides plebeius, Ruminococcus lactaris, and Bacteroides ovatus. Mechanism How each of these factors leads to excess fetal growth is complex and not completely understood. Traditionally, the Pedersen hypothesis has been used to explain the mechanism by which uncontrolled gestational diabetes can lead to macrosomia, and many aspects of it have been confirmed with further studies. It has also been shown that different patterns of excess fetal growth are seen in diabetic associated macrosomia compared to other predisposing factors, suggesting different underlying mechanisms. Specifically, macrosomic infants associated with glucose abnormalities are seen to have increased body fat, larger shoulders, and abdominal circumference. == Maternal Lipid metabolism ==

During pregnancy, the levels of fat (lipids) in a mother's blood can influence how the baby grows. Studies have shown that higher levels of triglyceride and remnant cholesterol early in pregnancy are linked to faster fetal growth and a greater chance of the baby being born larger than average for its gestational age. Later in pregnancy, higher total cholesterol in the mother's blood has also been linked to higher birthweight, supporting the idea that maternal lipid levels can directly affect the baby's growth. == Diagnosis ==

Diagnosing fetal macrosomia cannot be performed until after birth, as evaluating a baby's weight in the womb may be inaccurate. Variability of fetal weight estimations has been linked to differences due to sensitivity and specificity of ultrasound algorithms as well as to the individual performing the ultrasound examination. In addition to sonography, fetal weight can also be assessed using clinical and maternal methods. Clinical methods for estimating fetal weight involve measuring the mother's symphysis-fundal height and performing Leopold's maneuvers, which can help with determining the fetus's position in utero in addition to size. == Prevention ==

LGA and fetal macrosomia associated with poor glycemic control can be prevented by effective blood glucose management below a mean blood glucose level of 100 mg/dl before and during pregnancy; additionally, closely monitoring weight gain and diet during pregnancy can help to prevent LGA and fetal macrosomia. Women with obesity that undergo weight loss can greatly decrease their chances of having a macrosomic or LGA infant. In conclusion although exercise does help reduce some of the risk factors associated with GDM it does not completely prevent it. The study also concluded that regular moderate intensity training does help decreasing the risk of maternal weight gain, c-sections and macrosomia. == Screening ==

Most screening for LGA and macrosomia occurs during prenatal check-ups, where both fundal height and ultrasound scans can give an approximate measurement of the baby's proportions. Two-dimensional ultrasound can be used to screen for macrosomia and LGA but estimations are generally not precise at any gestational age until birth. == Management ==

An approach that is sometimes suggested is to induce labor close to the estimated due date (at term) or near that date. The rationale is that by the baby being born with a lower birth weight, there would be a lower risk of long labors, cesarean section, bone fractures, and shoulder dystocia. A number needed to treat analysis determined that approximately 3,700 women with suspected fetal macrosomia would have to undergo an unnecessary cesarean section to prevent one incident of brachial plexus injuries secondary to shoulder dystocia. The use of metformin to control maternal blood glucose levels has shown to be more effective than using insulin alone in reducing the likelihood of fetal macrosomia. There is a 20% lower chance of having an LGA baby when using metformin to manage diabetes compared to using insulin. Modifiable risk factors that increase the incidence of LGA births, such as gestational weight gain above recommended BMI guidelines, can be managed with lifestyle modifications, including maintaining a balanced diet and exercising. Such interventions can help mothers achieve the recommended gestational weight and lower the incidence of fetal macrosomia in obese and overweight women. == Epidemiology ==

In healthy pregnancies without pre-term or post-term health complications, fetal macrosomia has been observed to affect around 12% of newborns. Thus, women in Europe and the United States, with higher gestational weight gain, tend to have higher associated risk of LGA infants, macrosomia and cesarean. In general, rates of LGA infants have increased 15-25% in many countries including the United States, Canada, Germany, Denmark, Scotland and more in the past 20–30 years, suggesting an increase in LGA births worldwide. == References ==