The average newborn weighs about 3.4kg (7lb 8oz). Babies weighing more than 4kg (8lb 13oz) at birth are considered larger than average, or macrosomic. If you have a very large baby, weighing 4.5kg (9lb 15oz) or more, it can put you and your baby at greater risk of certain complications.
Although many women give birth to very big babies without any problems, it's common to need a bit of help. Macrosomia may place the mother and fetus or neonate at risk for adverse outcomes. Antenatal risk factors reportedly predict macrosomia at birth. Identification of these at-risk pregnancies may allow intervention to reduce the risk, to provide appropriate counseling, and to implement appropriate plans for monitoring and follow-up care during pregnancy and after delivery. Gestational age is associated with macrosomia. Birth weight increases as gestational age increases.
Fetal sex influences macrosomic potential. Male infants weigh more than female infants at any gestational age. Recent studies have confirmed this association. Diabetes that is poorly controlled in pregnancy is the greatest risk factor for fetal macrosomia. This is believed to be partially explained by excessive growth due to elevated maternal plasma glucose levels and resulting elevated insulin and insulinlike growth factor levels, which stimulate glycogen synthesis, fat deposition, and fetal growth. Excessive maternal weight gain and/or prepregnancy weight also play the same role in macrosomia by providing excessive growth in selected cases. The reason for this undiagnosed glucose intolerance in these individual needs to be studied.Genetic factors also contribute to fetal size. Taller and heavier parents typically produce larger offspring.
Fetal macrosomia can cause a baby to become wedged in the birth canal, sustain birth injuries, or require the use of forceps or a vacuum device during delivery. Increased risk of cesarean delivery is the primary maternal risk factor associated with macrosomia. Genital tract lacerations during childbirth, fetal macrosomia can cause a baby to injure the birth canal — such as by tearing vaginal tissues and the muscles between the vagina and the anus (perineal muscles). Uterine Bleeding after delivery. Uterine rupture, fetal macrosomia increases the risk of uterine rupture of the previous Uterine C-Section. Although rare, shoulder dystocia is the most serious complication associated with fetal macrosomia. Fracture of the clavicle and damage to the nerves of the brachial plexus are the most common fetal injuries associated with macrosomia.