There are approximately 3.9 million deliveries in the United States every year. Fortunately, most of these deliveries are appropriately anticipated and occur in the hospital with trained staff. Because deliveries occur so infrequently in the prehospital setting, initial effort should be directed toward getting the mother quickly to a hospital with obstetric and gynecological care. There, well-trained providers can deliver the baby in a controlled setting with adequate equipment, and expertise should complications arise. However, there may not always be enough time to get the mother to the appropriate facility, for this reason, it is crucial for emergency medical service (EMS) providers to be familiar with the appropriate delivery technique. 
A bony ring formed by the sacrum, ischium, ilium, and pubis. The fetus must pass through this ring during delivery, and its size and shape significantly impact the ease of delivery.
A fibromuscular tubular structure that forms the base of the uterus and leads into the vagina. During labor, it dilates and becomes much thinner, to accommodate the passage of the fetus.
A hollow muscular, pear-shaped shaped structure in a females lower abdomen/pelvis. During pregnancy, it houses the fetus, placenta, amniotic sac, and fluid and can grow rapidly to accommodate these enlarging structures. During labor, the uterus generates powerful muscular force that helps expel the baby.
The fundus is the part of the uterus that forms a rounded dome on the top of the uterus. Fundal height is an important measurement for determining the age of the fetus.
Stages of Labor
There are 4 stages of labor. Delivery of the fetus occurs in the second stage of labor.
Indications that it is time for the mother to give birth include a strong urge to push, more intense contractions occurring every 2 to 5 minutes, and the fetal head beginning to crown.
There are not any contraindications to delivery. If the mother's labor is progressing to the point that she is about to deliver, there is little the prehospital provider can do to prevent it. If the EMS provider is close to the hospital and wishes to delay delivery until arrival, discouraging the woman from pushing may delay the delivery for a short while.
For most uncomplicated deliveries minimal equipment is necessary. In the prehospital setting, you should ideally have something to cut and clamp the umbilical cord, and something to dry and stimulate the infant such as a towel. In emergency settings, typical obstetric and gynecological equipment may not be available, but if possible EMS providers should try to have the following items ready:
In prehospital delivery, the EMD provider must make due with the personnel available. Ideally, the EMT or paramedic performing the delivery should have at least one assistant.
Before labor is fully underway, place the mother in the dorsal lithotomy position. To achieve this position, you will have the mother lay on her back (supine) with her feet/lower legs above her hips. Ideally, the patient would be able to rest their heals in stirrups, but these are rarely available. An assistant can instead help hold the mother's legs up. Prior to delivery the vulva/perineum should be cleaned with a sterile saline solution. It is also a good idea to tuck a chuck or sterile towel under the mother's buttock as this with help contain products of conception and make for easier cleanup. 
Second Stage of Labor
Around the time of delivery, the patient will begin experiencing strong contractions around 2 to 4 minutes apart. When the mother is experiencing a contraction, be sure to coach the mother by encouraging her to push for a full 10 seconds, if possible. This process can be quite exhausting for the mother, so generally, the mother is encouraged to push for 3 sets of 10 seconds during a contraction then take a break. Peri-vaginal tears are a common complication of delivery. These occur when the baby's head is forcefully and quickly expelled from the vagina. To prevent lacerations, as the mother is pushing, place one hand on the babies scalp, applying pressure and allowing for a slower and more controlled expulsion of the babies head from the vagina. The other hand can be used to place pressure on the perineum, providing this area with support as this is the most common area for a laceration.
Once the head is delivered, sweep fingers around the baby's neck feeling for a nuchal cord. If you feel the umbilical cord wrapped around the child's neck, you will need to reduce the cord.  At this point, you will need to deliver the shoulders, with the child's head facing the mother's inner thigh, grasp the child's head and pull downward with gentle traction. This will help release the child's anterior shoulder from catching on the mother's boney pelvic rim. Then gently pull upward releasing the posterior shoulder. From here, the passage of the rest of the body should happen quickly and spontaneously, with little effort on your part.
Next, clamp and cut the umbilical cord. There is no rush for the prehospital provider to clamp or deliver the placenta. It is advised to wait at least 30 seconds before clamping the cord; this allows for autotransfusion of some of the placental blood into the fetus. Generally, it is advised that the proximal umbilical clamp is placed approximately 10 centimeters from the child's umbilicus. This provides adequate spare cord to place an umbilical catheter if necessary once the child reaches the hospital if they require neonatal resuscitation. The second clamp should be placed approximately 5 cm apart from the first, this will allow adequate space to safely cut the umbilical cord with a sharp pair of scissors. 
The infant is now free from the mother. If available, use a bulb syringe to suction the child's mouth then nares, and with a clean towel dry and stimulate the infant. As it is unlikely that an ambient warmer will be available in the prehospital setting, skin to skin contact between child and mother is strongly encouraged. This promotes bonding and helps keep the child warm.
Third Stage of Labor
After the baby has been successfully delivered, the placenta must be delivered. This should occur between 5 and 30 minutes after delivery. While waiting for the placenta to deliver, apply gentle traction on the cord. The cord can be quite slippery, so it is best to hold onto the cord with either a needle driver, Kelly forceps, or a hemostat. Applying fundal pressure/uterine massage will stimulate uterine contraction, promoting the placental release and preventing post-partum hemorrhage. The placenta is ready to deliver when the uterus becomes more firm, there is a gush of blood from the vagina, and there is a lengthening of the umbilical cord. These are a consequence of the placenta separating from the uterine wall and beginning its descent.
Slowly increase the amount of traction on the cord until placenta begins to descend. Once the placenta is visible, grab it, continuing to pull downward. Once the placenta is approximately halfway out of the vaginal os, begin to twist the placenta as you continue to pull. This will cause the stringy delicate membranous tail of the placenta to wrap around itself, providing greater structural integrity, preventing retained products of conception. Once the placenta has been delivered, it needs to be inspected for any missings pieces. If the placenta is not intact, the retained products will need to be retrieved to prevent bleeding or later infection.
Shoulder dystocia is one of the most common intrapartum pregnancy complications. It occurs when the width of the fetus's shoulders is too broad to fit through the mother's pelvic outlet, resulting in the fetus becoming lodged in the birth canal. This complication is difficult to anticipate, but risk factors include macrosomia, maternal diabetes, maternal obesity, and fetal postdates. It is important to quickly recognize and treat this complication because prolonged dystocia can result in fetal asphyxiation, clavicle fracture, and brachial plexus injury.
The presence of "turtle sign can identify shoulder dystocia." This phenomenon is where the fetal head pops in and out of the vaginal canal, like a turtle sticking its head out of its shell. This occurs because as the mother pushes, the fetal head is expelled, but because the fetal shoulders are stuck behind the pelvic rim when the mother stops pushing the head gets pulled back into the vaginal canal.
There are several maneuvers to resolve the dystocia. In the McRoberts maneuver, from the lithotomy position, forcefully push the mother's thigh's back onto her abdomen/chest, resulting in hyperflexion at the hips. This moves the pubic symphysis up and back allowing more room for the passage of the anterior shoulder. If this is not sufficient, with the fist, one can apply downward suprapubic pressure. In this location, the EMS provider's fist should be directly over the anterior shoulder, thus pushing it down and freeing it from obstruction.
Umbilical Cord Prolapse
Cord prolapse is when during delivery, a loop of the umbilical cord begins to stick out past the fetus. This usually occurs when the body of the fetus does not fill the birth canal. Thus, there is room for the umbilical cord to slip out. This is concerning because as the delivery progresses the body of the fetus can compress the cord, inhibiting oxygenated blood from getting to the baby. These patients should be taken to a facility capable of performing the cesarian section. If umbilical prolapse occurs, instruct the mother to stop pushing, and place the mother in Trendelenburg position. Attempt to lift the presenting fetal part (usually the head) off of the umbilicus and hold it up until patient care can be handed off at the hospital.
Postpartum hemorrhage is when the mother loses more than 500 mL of blood after vaginal delivery of the baby. It is one of the main causes of pregnancy-related maternal death worldwide. There are many causes of postpartum hemorrhage, and much of the treatment involves getting the patient to a hospital with sufficient OB/GYN resources, but there are a number of things the prehospital provider can do to help in this situation. Just as if this was a hemorrhage from trauma, it is important for prehospital personnel to take the patients vitals, establish IV access, and administer fluids if necessary.
The most common cause of postpartum hemorrhage is uterine atony. Normally, the uterus begins to contract after the baby has been successfully delivered spontaneously. Thus, the myometrium effectively clamps down on the spiral arteries preventing further blood loss. Vigorous massage of the uterine fundus can be implemented to help initiate uterine contraction. If this is insufficient, bimanual uterine massage can be done by placing one hand in the vagina and the other on the abdomen over the fundus and compressing the uterus between the hands.
While prehospital deliveries are uncommon procedures for EMT and paramedics, it is important to be familiar with the proper delivery technique. This will help the provider remain calm during the procedure. For the most part, uncomplicated deliveries will happen with little effort. Key aspects of the delivery are controlling the expulsion of the fetal head and delivery of the anterior shoulder. Quickly place the baby on the mother's chest, because skin to skin contact will prevent fetal hypothermia. EMS providers should also be able to troubleshoot some of the more common pregnancy complications such as shoulder dystocia, umbilical cord prolapse, and post-partum hemorrhage.