There is a lot of chatter whenever a larger baby is born and exceeds a hospital’s record. The media storm that follows, social and mainstream, makes for the viral nature of the images. Something about a newborn who is the size of a three-month-old is universally compelling, but it does not always mean a beginning without problems. Like with most things, the knowledge a baby is big or small without putting it into vital context is just data, not meaningful information.
Some smaller newborns are healthier than their bigger counterparts. For example, a more common occurrence for a larger newborn is one born to a mother with gestational diabetes. In the womb, that infant basically was exposed to high levels of sugar (aka glucose) and gets overgrown. Birth precipitously drops their influx of glucose that was in constant supply for the nine months inside mom, so they actually may require frequent monitoring in the first few days of life to offset their blood sugar going too low (eg hypoglycemia) which can cause untoward brain effects.
A larger baby might challenge the mechanics of delivery and warrant a surgical one or a traumatic, complex vaginal birth. Birth complications like a shoulder dystocia where the infant gets stuck can lead to a clavicle fracture or brachial plexus injury. All the while, mom can acquire problems too as a secondary effect.
There are genetic conditions like Beckwith-Wiedemann that cause an overgrowth syndrome impacting multiple organ systems. Depending on the severity and spectrum of the individual case, breathing and swallowing difficulties can arise due to a baby’s excessively large tongue, abdominal wall defects can expose internal contents, and their risk for cancers is considerably increased. Thankfully, most do very well and live long, fulfilling lives.
The baby’s size in isolation is not the most valuable piece of data. In fact, prenatal ultrasounds, since they can be so technician-dependent, routinely wrongly estimate weight. It is the trajectory of growth that is most important and whether it is proportional. It is this understanding of the comprehensive clinical picture (eg maternal clinical status, parental height/weight, family history, pregnancy history) along with the overall prenatal development that tells a more accurate story.
The best news is we live during a time we can anticipate much of the issues a larger baby might experience since consistent prenatal care pays the greatest dividends. Therefore, most do quite well and many have minor to no concerns at birth. It is a wonderful moment in history to be born.