The placenta is a temporary organ that develops in the uterus during pregnancy, serving as a crucial connection between the pregnant person and the developing baby. This disc-shaped organ delivers oxygen and nutrients from the parent’s bloodstream to the baby through the umbilical cord. It also removes waste products, such as carbon dioxide, from the baby’s blood, transferring them back to the parent’s system for elimination. Healthcare providers obtain information about the placenta’s location during prenatal care.
Identifying Placental Position on Ultrasound
Ultrasound is primarily used to determine the placenta’s position within the uterus. During a scan, typically performed around 18 to 21 weeks of pregnancy, sound waves generate images of the uterus and its contents. The placenta appears on the ultrasound screen as a homogeneous, uniformly echogenic area, meaning it has a consistent texture and reflects sound waves uniformly. Sonographers carefully scan the uterine walls to pinpoint where this structure is attached, observing its relationship to the cervix and other uterine regions.
Common Placental Locations
The placenta can implant in various locations within the uterus. Several terms describe these common positions. An anterior placenta is attached to the front wall of the uterus, closer to the abdomen. A posterior placenta is situated on the back wall of the uterus, closer to the spine. When the placenta implants at the very top of the uterus, it is referred to as a fundal placenta. The placenta can also attach to either the left or right side of the uterus, known as a lateral placenta. These positions are considered normal variations of placental placement.
Understanding a Low-Lying Placenta
A low-lying placenta, sometimes referred to as placenta previa, occurs when the placenta is positioned close to or covering the cervix, the opening of the uterus. It is considered low-lying if its edge is less than 2 centimeters away from the cervix. This position is often identified during the routine 18-to-22-week ultrasound scan. Many low-lying placentas diagnosed early in pregnancy will “migrate” upwards and away from the cervix as the uterus grows and expands. This natural movement means that most cases resolve on their own by the third trimester.
Implications of Placental Location
For most common placental locations, such as anterior, posterior, fundal, or lateral, the position generally does not have a significant impact on the pregnancy or delivery. An anterior placenta might cushion fetal movements, making them feel weaker or appear later. For a low-lying placenta, ongoing monitoring is recommended with follow-up ultrasounds, usually around 32 weeks, to check if the placenta has moved. If the placenta remains low or covers the cervix later in pregnancy, healthcare providers will discuss appropriate management and delivery options to ensure the safety of both the pregnant person and the baby.