When a baby is born vaginally, there is a specific order in which parts of their body emerge. The part of the baby that comes out first during labor and delivery is called the “presenting part.” Knowing what part of the baby comes out first can help parents-to-be understand what to expect during childbirth.
The Baby’s Head Is Usually the First Part Out
In most vaginal births, the baby’s head emerges first. The head is the hardest and largest part of the baby’s body, so it usually leads the way through the birthing canal. As the head moves down into the pelvis, it flexes to fit through the narrow space. This is called the “cardinal movement” of labor.
Once the baby’s head reaches the pelvic floor, it extends back so the chin can come out from under the pubic bone. Then the top and back of the head become visible. This is referred to as “crowning” and signals that birth is imminent. After crowning, the head continues rotating to align the widest part of the head (the parietal diameter) with the widest part of the pelvic outlet. This helps the head pass through the birth canal more easily.
When the head is delivered, it often turns to one side. This allows one shoulder to enter the pelvis next. The body then usually follows in a smooth motion, completing the delivery of the baby.
Reasons the Head Comes Out First
There are several reasons why the baby’s head typically emerges before the rest of their body during vaginal delivery:
- The head is the largest and widest part of the baby’s body, so it naturally leads the way through the birth canal.
- The shape of the pelvis encourages the baby’s head to descend first.
- The strong contractions of labor help flex the head forward so it can fit through the pelvis.
- The head is hard and rounded, allowing it to slide through the birth canal more easily than other body parts.
- The head contains vital organs like the brain, so it needs to emerge first to start breathing.
In the optimal birthing position, the baby descends through the pelvis headfirst, allowing the smallest diameter of the head to pass through the pelvic outlet. This makes delivery of the head smooth and minimizes trauma to the head and birth canal.
Breech Births: Feet or Buttocks Come Out First
In about 3-4% of pregnancies, the baby is in a breech position before birth. This means their buttocks or feet are pointed toward the pelvic outlet, rather than their head. With breech births, the buttocks or feet will be delivered first:
- Complete breech: The baby’s buttocks come out first, with legs folded at the knees and feet near the buttocks.
- Frank breech: The baby’s buttocks come out first, with legs extended up in front of the body.
- Footling breech: One or both of the baby’s feet come out first, with legs extended downward.
After the buttocks or feet are delivered, the torso emerges. Then the arms and head pass through the pelvis last. Breech deliveries carry more risks for the baby, so most providers will recommend a cesarean section for breech babies.
Reasons for Breech Position
Some potential causes of breech position include:
- Prematurity
- Low amniotic fluid
- Abnormal uterine shape
- Placenta previa
- Multiple babies
- Lax uterine or abdominal muscles
Sometimes there is no identifiable cause. First-time mothers are also more likely to have a breech baby. Providers may try turning the baby headfirst using external cephalic version before considering a cesarean.
Other Labor Presentations
While most babies are head or buttocks first, other labor presentations are possible:
- Face first: The baby’s head is hyperextended, so the face comes out first instead of the crown of the head. This is very rare.
- Brow first: The baby’s head is partially flexed, resulting in the brow emerging first. This is also uncommon.
- Shoulder first: One of the baby’s shoulders emerges before the head. This typically occurs in larger babies or very small pelvises.
These alternative presentations often lead to obstructed labor and may require intervention like a cesarean. Babies in anomalous positions can maneuver into a better position spontaneously but may need guidance from providers.
What Determines the Baby’s Position?
The eventual position of the baby results from a combination of factors:
- The shape and capacity of the mother’s pelvis
- The size and orientation of the uterus
- The amount of amniotic fluid
- The number of babies (multiple pregnancy)
- The baby’s size and shape
- Genetics
- Whether it is the mother’s first pregnancy
- The strength of uterine contractions
- How the baby moves in response to contractions
The baby’s position several weeks before birth is not necessarily the position they will have during delivery. Most babies turn head down by week 37. But some flip into breech position at the last minute, while others may get into an oblique or transverse lie.
Methods to Turn Breech Babies
If a prenatal exam shows the baby is breech, there are several techniques providers may use to try flipping them headfirst:
- External cephalic version: The provider pushes on the abdomen to turn the baby.
- Chiropractic adjustment: Gentle manipulation of pelvic alignment to create more room for the baby to turn.
- Acupuncture or moxibustion: Done on points believed to encourage fetal movement.
- Exercises: Certain positions and motions thought to give the baby more space.
These methods have varying degrees of success. Babies with certain conditions are less likely to turn and may require a scheduled C-section. Consult your provider about options if your baby is breech.
Stages of Labor
For a baby in the vertex position, labor progresses through several stages:
- Early labor: Contractions begin but are mild. The cervix begins thinning and dilating up to 6 cm.
- Active labor: Contractions increase in intensity and frequency. Cervix dilates from 7-10 cm.
- Transition: Cervix fully dilates to 10 cm as the baby descends deep into the pelvis.
- Pushing/birth: Involuntary pushing urges start as the baby moves through the vagina and is delivered.
- Delivery of the placenta: The placenta detaches from the uterine wall and is pushed out.
Early and active labor can take many hours for first-time mothers. Pushing and delivery is often the quickest phase, lasting minutes to hours. Breech births may involve maneuvers like assisted breech delivery based on the position.
Head Engagement and Station
As the baby’s head descends into the pelvis, providers assess its progress by “station.” This refers to the head’s position relative to the ischial spines, bony protrusions in the pelvis:
- Station 0 means the head is at the spines.
- A lower station number (like -3) means the head is higher.
- A higher number (like +2) means it is lower in the pelvis.
When the head “engages” in the pelvis around station -3 or -2, it is unlikely to rise out of the pelvis again before labor. Engagement helps confirm the baby is positioning for vaginal delivery.
Assessing Dilation and Effacement
Providers also monitor the progress of labor by assessing dilation and effacement:
- Dilation: Opening of the cervix from 0-10 cm.
- Effacement: Thinning of the cervix from 0-100%.
These metrics, along with station and contraction pattern, help providers evaluate if labor is progressing normally. Abnormal progress may be a sign that intervention is needed.
Impact of Labor Position
The mother’s position during labor can influence how the baby moves through the birth canal:
| Birth Position | Potential Benefits |
|---|---|
| Upright positions (sitting, squatting, kneeling) | Allows pelvis to open wider, may shorten labor |
| Lying on back | Convenient for providers assisting delivery |
| Side-lying | Comfortable resting position during early labor |
| Hands and knees | Uses gravity to encourage baby into optimal position |
Changing positions frequently can help labor progress and make the mother more comfortable. Walking and upright positions may help the baby descend into the pelvis. Lying down may be necessary for procedures or delivery assistance.
Positions to Manage Breech Birth
Special positions are used to aid vaginal breech delivery:
- Lithotomy position: Lying on back with legs in supports to allow access to perineum.
- All fours: Provides room for baby’s body to dangle until head emerges.
- Upright kneeling or squatting: Uses gravity to help baby descend.
Having room for the provider to intervene is essential since breech delivers have more risks and requirements.
Supporting the Perineum
As the baby’s head crowns, the perineum must stretch extensively to allow passage. Tears can occur if the perineum is not supported:
- 1st degree tear: Superficial tearing of vaginal tissue.
- 2nd degree tear: Deeper tear extending into perineal muscles.
- 3rd degree tear: Tearing through anal sphincter muscles.
- 4th degree tear: Tearing through rectal lining.
Many techniques can help prevent or minimize perineal tears:
- Warm compresses to increase tissue elasticity.
- Perineal massage in late pregnancy.
- Slow, controlled delivery of the head.
- Hand support of the perineum during crowning.
- Episiotomy (surgical cut to enlarge vaginal opening).
Involving the mother in pushing and breathing can help control the speed of delivery. Tears should be promptly assessed and repaired after birth.
Delivering the Placenta
After the baby is born, there is still one more very important step – delivery of the placenta. This typically occurs within 5-30 minutes of birth.
There are three stages of placental delivery:
- Separation: The placenta detaches from the uterine wall.
- Descent: The placenta moves down into the cervix.
- Expulsion: The placenta exits the vagina with gentle traction on the umbilical cord.
It is vital to ensure the placenta fully separates and the uterus contracts down firmly after delivery. Continued bleeding could signal a placental fragment or blood clot remains inside the uterus.
Examination of the Placenta
The delivered placenta is examined to ensure it is intact. The main aspects assessed are:
- Placental shape and measurements
- Umbilical cord length and number of vessels
- Presence of placental calcifications
- Missing sections or abnormal formations
This evaluation can provide insight into any placental problems that may have affected the pregnancy.
Special Situations and Risks
While most babies are positioned head first, there are circumstances that can alter labor progression or necessitate intervention:
- Prematurity: Early labor resulting in a low-birth-weight baby.
- Multiples: Unique risks present with twins or more sharing the uterus.
- Fetal anomalies: Medical issues may cause an abnormal presentation.
- Small pelvis: Contracted pelvis dimensions can prevent vaginal delivery.
- Cephalopelvic disproportion (CPD): Baby’s head is too large for the mother’s pelvis.
- Prolonged labor: Failure to progress normally in the stages of labor.
- Distressed baby: Changes in fetal heart rate signaling problems.
These situations often lead providers to recommend a C-section for the safety of both mother and baby. Vaginal birth may still be possible with techniques to aid delivery.
Assisted Delivery Methods
If added intervention is needed during the pushing stage, there are some assisted delivery techniques that can be utilized:
- Vacuum extraction: A vacuum cup is attached to the baby’s head to provide gentle traction with contractions.
- Forceps: Spoon-shaped blades are applied around the baby’s head to help guide it out.
- Episiotomy: An incision to enlarge the vaginal opening if it is preventing delivery.
These interventions are sometimes used to avoid a C-section or safely deliver the baby more quickly if complications arise.
Potential Delivery Complications
Some other issues that can occur during labor and delivery include:
- Cord prolapse – Umbilical cord emerges before the baby
- Shoulder dystocia – Baby’s shoulder becomes stuck
- Postpartum hemorrhage – Heavy bleeding after birth
- Perineal laceration – Deep vaginal/perineal tears
Skilled OB providers are trained to rapidly identify and manage any delivery complications that arise to ensure the optimal outcome.
Conclusion
Knowing the typical order of birth and reasons behind it can help mothers prepare for bringing their baby into the world. While vaginal deliveries have a natural progression, every labor is unique. An experienced provider can guide the process and handle any variations or complications. With proper care, most babies can be safely delivered head or buttocks first through the birth canal in the majority of pregnancies.
