The placenta is a temporary organ that develops in the uterus during pregnancy. It connects the pregnant person to the fetus via the umbilical cord, facilitating the exchange of nutrients, oxygen, and waste products. The placenta acts as the baby’s lungs, kidneys, and liver before birth. Its placement within the uterus is a factor in a healthy pregnancy journey.
Optimal Placental Positioning
The placenta can attach to any part of the uterine wall, but certain locations are optimal for a healthy pregnancy. The most common positions include the fundal, anterior, and posterior placements. A fundal placenta is located at the top of the uterus and is typically associated with uncomplicated pregnancies.
An anterior placenta attaches to the front wall of the uterus, closest to the abdomen, and occurs in about half of pregnancies. A posterior placenta, conversely, attaches to the back wall of the uterus, closer to the spine. Both anterior and posterior positions are normal and healthy. These placements allow for appropriate fetal growth and do not generally interfere with the birthing process.
Placental Malpositions
Sometimes, the placenta does not implant in an optimal location, leading to conditions known as placental malpositions. One condition is placenta previa, where the placenta partially or completely covers the cervix, the opening to the birth canal. There are different types: marginal, partial, and complete. Marginal previa means the placenta is at the edge of the cervix but does not cover it. Partial previa covers a portion, while complete previa fully blocks the cervical opening. Complete placenta previa is less likely to resolve on its own.
Another condition is Placenta Accreta Spectrum (PAS), which involves the placenta attaching too deeply into the uterine wall. PAS includes three categories based on depth of invasion: placenta accreta, where the placenta firmly attaches to the superficial muscle layer; placenta increta, where it invades deeper into the muscle; and placenta percreta, where it grows through the entire uterine wall, potentially reaching nearby organs like the bladder or rectum. PAS disorders are more common in individuals with previous cesarean deliveries.
Vasa previa is a serious condition where fetal blood vessels cross over or near the internal opening of the uterus, unprotected by placental tissue or the umbilical cord. These exposed vessels are vulnerable to rupture during labor, which can lead to rapid fetal blood loss. Vasa previa can be associated with a velamentous cord insertion, where the umbilical cord attaches to the membranes instead of directly to the placenta, leaving vessels unprotected.
Understanding Placental Conditions
Placental location issues are identified and monitored through ultrasound scans. These scans are part of routine prenatal care, typically performed between 18 and 21 weeks. An initial abdominal ultrasound can determine the placenta’s position, and a transvaginal ultrasound may be used for more precise imaging, especially to assess its proximity to the cervix.
For a diagnosis of placenta previa, close monitoring is recommended. Many cases diagnosed early resolve naturally as the uterus grows and expands, causing the placenta to appear to “migrate” away from the cervix. If placenta previa persists into the third trimester, a cesarean delivery is planned to prevent complications such as severe bleeding during labor. In cases of placenta accreta spectrum, specialized care and a planned cesarean delivery are necessary due to the risk of significant blood loss. Healthcare providers closely monitor these conditions to ensure the safest outcome for both the pregnant person and the baby.
The Placenta’s Journey After Birth
Following the birth of the baby, the placenta undergoes its own delivery, which is known as the third stage of labor. This process typically occurs within 5 to 30 minutes after the baby is born. The uterus continues to contract, helping the placenta separate from the uterine wall.
For a vaginal birth, the delivering person may be asked to push, or medical staff might apply gentle pressure to the abdomen to assist in the placenta’s expulsion. If the baby was delivered via cesarean section, the placenta is removed by the healthcare provider through the same incision. Once delivered, the placenta is routinely examined to ensure it is intact and that no fragments remain inside the uterus, which could lead to complications. After examination, the placenta is typically treated as medical waste and disposed of by the hospital. Some individuals or families may choose to keep the placenta for personal or cultural reasons, such as burial or encapsulation, although scientific evidence supporting health benefits for practices like encapsulation is not established.