Your Baby's Growth and Development
By pregnancy week 18 your baby's heart is developed enough to show some signs of defects. Ultrasound may be used to help detect any structural abnormalities that might exist. Most babies will be born without any congenital abnormalities. If an early ultrasound does detect something abnormal, you can plan ahead for any interventions or surgeries that may be necessary to support your newborn baby after birth.

At pregnancy week 18 your baby is now starting to produce a protective covering along the nerves, called Myelin. This substance will be produced through the ninth month. By now your baby's genitals should be distinguishable, though you may not yet have the opportunity to view them at your health care practitioner's office.