Ultrasounds/Sonograms

Ultrasounds are given routinely at about 20 weeks with many providers now offering first trimester scans for dating gestation.

Ultrasounds are helpful in confirming due dates (most accurate in the first 10-12 weeks).  They can also be used to medically diagnose multiple pregnancies, placental problems (such as placenta previa--in which the placenta partially or totally covers the opening of the woman's cervix),  amount of amniotic fluid, as well as determine the baby's positioning prior to labor/delivery and some procedures (amniocentesis, etc. ).   Most often, the ultrasound is performed routinely to assure the parents and provider that everything "looks ok".  Parents can often be told the gender of their baby, assuming the baby cooperates!  Sizing of the baby from the ultrasound scan is a very big guessing game with accuracy depending on multiple variables.  The skill and experience  of the technician as well as the positioning of the baby are probably the biggest factors.  Probably the most common error/risk associated with the ultrasound is overestimating (or underestimating)  the baby's weight and basing a course of action on that estimate.  It has happened many times that a mother resigned to having a 10 pounder at full term, was induced a week or two early, only to find out that her baby was 7 1/2 to 8 pounds.  These sizing errors can often pose problems for the infant (particularly breathing) as they may not be ready for life outside of the womb just yet.  On the other hand,  I met a mother who had been told  that her baby was 8 1/2 pounds;  much to her surprise she gave birth naturally about one week later to a baby almost 11 1/2 pounds! 

The physical risks to the baby from ultrasound are still mostly uncertain.  Whereas ultrasounds work by sound wave energy--bouncing off of the baby to give the picture of him/her,  there have been some recent studies that  indicate that babies who are "seen" using ultrasound are 30-60% more likely to be of lower birth weight.  Other possible, but unconfirmed risks, may include:  later hearing difficulties, dyslexia, increased jaundice, and  adverse effects on immune system.  One study also suggests there is evidence of a link between ultrasound scans and higher leukemia rates.  There have been multiple studies on the benefits of ROUTINE scans and neither fetal nor maternal outcomes have been improved in the cases of the low risk woman. 

It appears so far that the baby might feel some heat, if anything,  from the ultrasound scan;  how much heat the baby feels, if at all,  is uncertain.  He/she might also hear the scan, since it is indeed, waves of sounds.  Some researchers have suggested that the sounds a baby might hear might be somewhat uncomfortable and similar to the decibel  of a nearby moving train.