Babies are usually delivered head first rather than feet first for a few important medical reasons. While most fetuses naturally settle into a head down position in preparation for birth, some babies end up in a breech presentation with their feet or buttocks pointed towards the birth canal. Delivering a baby feet first or breech can pose risks for both the baby and the mother. Understanding why babies should be delivered head first provides insight into fetal positioning, labor and delivery practices, and potential complications.
Why Do Most Babies Naturally Favor a Head Down Position?
The head down position, known medically as the vertex presentation, is the most common and optimal position for delivery. Between 96-97% of babies settle into this position by late pregnancy.[1] There are several theories for why vertex presentation is favored:
– Brain development: The fetus’ head contains the quickly developing brain and is therefore disproportionately heavy early on. This weight at the top encourages the head to naturally settle downward.
– Shape and size: The rounded head and narrow shoulders make it easier for the head to press into the pelvis and cervix. In contrast, the broader shoulders and body are more difficult to fit through the narrow birth canal.
– Movements and gravity: By the third trimester, the amount of room in the uterus decreases. This restricts larger movements and encourages the fetus to tuck its limbs in, causing the head to tilt downwards. The fetus may also settle head down in response to gravity.
– Evolution: Since bipedal humans have a narrower pelvis than quadruped mammals, a head-down position may have evolved to ensure a safer delivery.
What Are the Risks of Breech Birth?
While some babies naturally settle into a feet first breech presentation, this position can increase risks for both mother and child. Potential complications include:[2]
– Baby getting “stuck” during delivery and experiencing trauma
– Umbilical cord issues such as prolapse, compression, or squeezing
– Lack of oxygen to the baby during prolonged or difficult delivery
– Birth injuries such as brain bleeds, fractured bones, or nerve damage
– Perinatal mortality 2-5x higher than vertex presentation
Breech delivery also poses concerns for the mother:
– Increased likelihood of needing medical intervention like a c-section
– Greater risk of excessive bleeding or infection
– Prolonged labor and recovery time
– Potential uterine or pelvic floor injuries
Due to these increased risks, most providers will attempt to manually turn breech babies into a head-down position before labor begins. When this is not successful, a planned c-section is typically recommended for full-term breech pregnancies.
What Makes Head First Birth Safer?
Babies are designed to come through the birth canal head first for several important reasons:
– **The head is the smallest part of the body.** The bones of the skull are not firmly joined together at birth, allowing them to flex and mold to the shape of the mother’s pelvis. This enables the largest part of the fetus to fit through the narrowest part of the birth canal.
– **The head protects the brain and vital organs.** Coming out head first shelters the vulnerable brain, face, and vital organs inside the ribcage as they pass through the birth canal. This minimizes risk of damage.
– **The birth canal dilates more easily.** When the head presses down, it helps stretch the cervix and birth canal to aid in labor progression. The body may not dilate the cervix as effectively.
– **The head can act as a wedge.** With the head positioned in the pelvis, each contraction pushes it further into the birth canal, stimulating dilation. This “wedging” helps drive the body down during the final pushing stage.
– **Respiration is easier.** Once the head is delivered, the baby can take its first breaths while the shoulders and body exit. Coming feet first makes initial breathing more difficult.
– **Umbilical cord issues are minimized.** When the head emerges first, risks of cord compression, prolapse, or entanglement are greatly reduced compared to breech positions.
Therefore, head first delivery takes advantage of the shape and function of both the fetus and pelvis for a smoother, safer birth. When faced feet first, the wider body has more difficulty fitting through and can endanger both mother and child.
When Are Breech Births Appropriate?
While uncommon, there are some circumstances where a planned breech delivery may be appropriate. According to ACOG guidelines, a vaginal breech birth may be considered with:[3]
– A full-term pregnancy
– Frank or complete breech position (buttocks/feet down). Other positions often require c-section.
– Baby is average size and has a small head circumference
– No complications such as low amniotic fluid or placental issues
– Normal maternal pelvis confirmed by exam
– Healthcare provider experienced with breech techniques
However, over 90% of breech babies in developed countries are delivered by planned cesarean section. Most providers will only recommend vaginal breech birth if the mother is unable or unwilling to have a c-section after being informed of the higher risks.
Breech Birth Techniques
When a vaginal breech birth is attempted, providers may use special maneuvers to guide the baby safely through the birth canal:
Frank Breech: With buttocks presenting first face up, allowing the hips and legs to deliver before the head. The baby’s body must not extend too far before the head is delivered.
Assisted Breech: The provider manually flexes the head forward and keeps the baby’s body supported to enable breech delivery. Gentle traction is applied to the body at certain points.
Breech Tilt: The mother lies with her pelvis tilted upward 15-30 degrees using wedge-shaped cushions. This uses gravity to help keep the baby’s head flexed downward.
Mauriceau-Smellie-Veit: The provider applies pressure on the baby’s head through the perineum to keep the chin tucked and guide head expulsion after the body has delivered up to the neck.
Bracht Maneuver: If head expulsion is delayed, the provider may rotate the baby by swinging the legs upward in a gentle arc to release one shoulder at a time.
Piper Forceps: Forceps may be rarely used to grasp the baby’s head and control delivery if complications arise. However, use of forceps increases the risk of harming the baby.
When successful, these controlled techniques can reduce risks and allow a safe vaginal breech delivery. However, cesareans are still the standard practice for most breech presentations in developed countries today.
Can the Baby Be Turned from Breech Position?
To avoid the need for a breech delivery, there are some techniques that may encourage the baby to turn head down before labor:
– **External cephalic version (ECV):** The provider pushes the buttocks and head through the mother’s abdomen to manually flip the baby into vertex position. This is typically done near the due date. Success rates range from 58-93%.[4]
– **Chiropractic adjustments:** Gentle manipulation of pelvic muscles and ligaments may encourage the baby to turn naturally. Success rates vary widely.
– **Breech tilting:** Lying tilted head-down 15-30 degrees can use gravity to flip some breech babies. But success appears low.
– **Moxibustion:** Burning the herb moxa (mugwort) near the little toes may stimulate fetal movement through acupuncture meridians. Research shows varied success rates.
– **Knee-chest position:** Getting on hands and knees with hips raised higher than shoulders may allow the baby to flip on its own by utilizing gravity. But benefit is uncertain.
However, none of these methods are proven to be highly effective. If they fail to turn the baby head down, a c-section will likely be scheduled. After 36-37 weeks, options become more limited as the baby descends into the pelvis.
When Are Babies Too Big to Deliver Vaginally?
While almost all head-down babies can navigate the birth canal without issue, there are some cases where fetal size may necessitate a c-section. Potential reasons include:
– **Suspected macrosomia:** Babies estimated to be over 8 lbs 13 oz may have difficulty fitting through the pelvis, increasing the chance of shoulder dystocia during vaginal delivery. But weight estimates by ultrasound can be inaccurate.
– **Birth weight >9000 g (19 lb 12 oz):** Infants over this size are at substantially higher risk of birth trauma or asphyxia during vaginal delivery. Elective c-section is often recommended.
– **Birth weight 4000-4500 g (8 lb 13 oz – 9 lb 15 oz) with diabetes:** Infants of mothers with diabetes tend to have broader shoulders and body frames, increasing risks of shoulder dystocia.
– **Disproportionate fetal-pelvic ratio:** Mismatched size between the pelvis and predicted infant size based on clinical pelvimetry. May prompt elective c-section.
However, ultrasound weight estimates are imprecise. Routine elective c-sections for suspected macrosomia are controversial, except in diabetics. Most infants over 8 lbs 13 oz can still deliver vaginally. Operative vaginal delivery with vacuum or forceps may be utilized if needed. Ultimately, the provider must determine if vaginal delivery appears feasible on a case-by-case basis.
What Position Do Babies Need to Be In for C-section?
Cesarean deliveries are typically performed when babies are head down, face down, and engaged deep in the pelvis. This vertex position is ideal for several reasons:
– The incision is made low on the uterus where it is thinnest.
– The head can act as a wedge to prevent intestinal protrusion.
– The curve of the head fits the curve of the lower uterine segment.
– The body usually delivers easily once the head is out.
– The head emerging first allows baby to breathe while body is delivered.
This enhances safety, efficiency and outcomes. Breech or transverse lie positions often prompt classical or vertical uterine incisions with higher risks. Providers will sometimes try to turn these babies head down with ECV prior to c-section when feasible. Vertex positioning is strongly favored but not always essential for cesarean delivery.
Conclusion
While less than 4% of babies settle into a breech position, head down delivery is favored for good reason.[1] The shape and size of a baby’s head and shoulders make it far safer for the head to enter the pelvis first during childbirth. Attempting delivery feet first increases risks of complications for both mother and infant. Most breech fetuses should be delivered by planned c-section. However, vaginal breech birth may be appropriate in some cases when a skilled provider is available. Understanding why nature intends for babies to be born head first provides important insight into the birth process.