Parturition in Humans and Its Stages

It is the process of giving birth to a child, and the placenta from the uterus to the vagina is called parturition. It is also called the phase between labor to childbirth or delivery. The labor or childbirth process is called parturition, which occurs approximately 38 weeks after fertilization. This process consists of three distinct stages of labor. The first, the stage of dilation, begins with the onset of standard, hard contractions of the uterus and ends with complete dilation of the cervix.

Stages of Parturition

The parturition process usually occurs in 3 stages i.e. 

1. Dilation

Dilation is defined as the uterus beginning to enlarge and rupture the membranes. It also starts a bloody discharge progressively. Dilation is usually the first stage of the process of labor. It starts when the effaced cervix is 3 cm dilated. Though it varies across women and they might not even have been experiencing active contractions before reaching this stage. During this process, the cervix becomes combined into the lower segment of the uterus. Parturition shortens the mussels and upper segments. It is drawing upwards and the lower segment during a contraction, and gradual expulsive motion upwards.

When the cervix has enlarged, the presenting fetal part permits to descend enough to allow passage for the baby’s head. It is around 10 cm for a full-term baby, here the process of dilation is complete. The actual period of the labor process varies slightly, though the average duration for the active phase is around 20 hours.

During the active phase, the cervix will dilate at a rate of about 1 cm/hr for a woman who’s giving birth for the first time. For a woman who’s previously had a vaginal delivery, the rate is typically about 2 cm/hr. This concept has been explained with the help of Friedman’s Curve, which focuses on the standard rate of fetal descent and cervical dilation during active labor.

2. Expulsion

This second stage of parturition starts at full dilation and continues until birth. This parturition process commences when the cervix pressure of the uterus increases, and in turn, the uterus Ferguson reflex increases uterine contractions. At the start, the top portion is completely engaged within the pelvis, i.e., the widest diameter of the pinnacle has passed below the amount of the pelvic inlet. Thereafter, the head of the baby continues descending into the pelvis, then below the pubic arch, and finally out of the vagina.

The fetal head is assisted by extra maternal efforts or pushing down. The successful birth of the marks the completion of the second stage of parturition. Important factors, such as parity, fetal size, anesthesia, will cause variations in the second stage of delivery.

3. Placental

This third stage of parturition starts after birth and ends with the delivery of the placenta. The normal duration between the delivery of the baby and the placenta varies between 10–12 minutes. It is often managed by giving a uterotonic, like oxytocin, together with appropriate cord traction. A fundal massage that is administered by a qualified birth attendant assists in delivering the placenta. Alternatively, it is allowing the placenta to be expelled without medical assistance.

The infant is more often than not born with the membranes still intact when the amnios have not ruptured during labor or pushing. It is often mentioned as being taken within the caul. It does not cause any harm, and moreover, the membranes can be easily wiped and broken away.

Medications During Parturition

Pain during parturition can be relieved or reduced by systemic drugs, psycho prophylaxis, regional nerve blockers, or the combination of these drugs.

Since the 1930s, psycho prophylaxis drugs have gained popularity as they prepare a woman both mentally and physically to prepare for childbirth thereby anticipating her to cope up with the pain during the process. Moreover, a comfortable environment, support of family and friends and a competent health assistant can help her to reduce the requirement for pharmaceutical pain relief.

Let us discuss these drugs one by one.

• Systemic drugs- Morphine and meperidine are common narcotic drugs given intravenously for pain relief (analgesia) during labour. However, some side effects are also associated with them such as vomiting and nausea. When meperidine and promethazine are given together the side effects are reduced. Other maternal side effects of these drugs include drowsiness, hypotension (low blood pressure), respiratory depression, etc. These drugs can cross the placental barrier causing the same effects in newborns. Butorphanol is another common systemic drug given in labour pain and is known for its less neonatal depression production.

• Barbiturates- These drugs are given for lessening the labour pain. However, they are rarely used during parturition. They are sedatives that can induce a relaxed state. They can’t provide effects like analgesics to reduce pain. If barbiturates are administered during active labour, it can cause respiratory depressions to the newborns which can be further reduced by the use of narcotic analgesics.

• Sedatives- These are used in the early stages of parturition to relax the woman against the contractions of active labour.

• Local anaesthesia- These drugs are an alternative to systemic drugs. Local anesthetic drugs work by prohibiting the conduction of nerve impulses. Their actions are limited to the site of injection as they can diffuse to short distances. They numb only the isolated body part and allow the woman to have control over the rest of her body. Local anesthesia doesn’t cause rigorous harmful effects to the woman as well as the newborn.

• Pudendal block- It is a common process that numbs the perineum and the birth canal for spontaneous delivery, vacuum extraction and forceps delivery. Anaesthetic drugs like lidocaine and bupivacaine are used and are injected into the pudendal nerve through the vagina. This technique is effective to reduce the pain from perineal distention but not from uterine contractions.

Operative Obstetrics

The majority of women can deliver a baby spontaneously. However, complications before, during or after the labour can put the lives of both mother and child at risk and may involve the intervention of a physician. 

• Cesarean Section- When a mother is unable to deliver the child through the vagina, the cesarean incision process is used. In this process, surgical incisions are made in the abdomen and the uterus. This procedure is only performed in severe cases where the risks of vaginal delivery to the mother and the foetus are greater than the abdominal delivery. Common indications include premature delivery for medical conditions, labour to progress, fetal distress, etc.

• Forceps delivery- It is a type of assisted vaginal delivery. It is sometimes required in vaginal childbirth. In this delivery, a health assistant applies forceps (an instrument having a shape of paired large spoons or salad spoons) to the baby’s head to pull out from the birth canal. This is done during a contraction when a mother pushes it voluntarily.