You might have heard that how your baby is positioned in pregnancy makes a difference to your labor and birth.
Perhaps you took a look at your pregnancy notes and saw your doctor had written something about ‘left occiput anterior, LOA’ and you’re wondering what it means when baby is LOA?
Let’s look at what the left occiput anterior position is and what it means for your birth.
What does left occiput anterior mean?
In left occiput anterior (LOA) the ‘O’ refers to the baby and the ‘L’ and ‘A’ refer to the mother.
It’s easy to remember if you think ‘pregnancy’: The ‘O'(baby) is inside the ‘L’ and ‘A’ (mother).
The occiput refers to the back of the baby’s head. Left anterior refers to the mother’s pelvis.
Let’s imagine the pelvis as a clock:
- The front or the pubis would be 12 o’clock
- The back or the sacrum is at 6 o’clock
- The left side is at 9 o’clock
- The right side is at 3 o’clock.
In an LOA position, the back of the baby’s head and the baby’s back are in between the mother’s left hip and pubic bone (around 10:30 on our imaginary pelvic clock).
Left occiput anterior presenting part
During pregnancy and labor the presenting part is the part of the baby which leads the way through the birth canal.
When the baby’s positioning is head down, the baby flexes her head, tucking her chin to allow a proper engagement in the pelvis.
When the head is in this position, the top part of the baby’s head, just above the occiput, becomes the presenting part.
Healthcare professionals call this presenting part the vertex.
When the baby’s position is LOA, the head is much more able to flex into the proper position.
What are the other fetal positions?
Now that we know the ‘O’ is for the baby and the rest of the letters refer to the woman’s pelvis, let’s explore other positions babies might adopt when entering the pelvis.
Right occiput anterior
Right occiput anterior (ROA) means the baby’s back is between the mother’s front and right side of her pelvis (1:30 on the clock).
You can read more in Right Occiput Anterior | What It Means When Baby Is ROA.
Left occiput transverse
Left occipito transverse (LOT) is when the baby enters the pelvis completely sideways. The baby’s back is on the mother’s left side (9 o’clock).
Right occiput transverse
You might have guessed this one. ROT is when the baby’s occiput is by the mother’s right hip (3 o’clock).
Left occiput posterior
In the circumference of the pelvis there is a position for every way the baby’s head enters. When the baby is in the left occiput posterior position (LOP) his back is towards the left side of his mother’s back (7:30 on the clock).
Right occiput posterior
ROP is another occiput posterior position. This time baby’s position is with her back towards her mother’s right side (4:30 on the clock).
Direct OA or OP
You might wonder why, in this clock analogy, I haven’t mentioned the positions where the baby’s back is at 12 or 6 o’clock.
These positions are called the direct occipito-anterior position (12 o’clock), and the direct occipito-posterior position (6 o’clock).
This is because the pelvis space the baby must navigate is not a circle, but is elliptically shaped.
The top ellipse (the pelvic inlet) where the baby engages at the end of pregnancy and at the beginning of labor is wider in its transverse diameter (from 9 to 3 o’clock) and the baby’s head won’t fit in a direct OA/OP position (from 12 to 6 o’clock).
Direct positions only happen at the end of labor, when birth is close and the baby has passed that top ellipse.
Then, babies must navigate the bottom ellipse (the pelvic outlet) where its anteroposterior diameter is wider.
When babies are in a direct OA/OP position, this means the head is very low down in the birth canal and birth is quite imminent.
Look at this video about the female pelvis, its diameters, inlet and outlet.
Non head-down positions
All the positions above are head-down positions.
When the baby is breech, whether frank breech (when baby’s feet are up and the presentation is just the bottom) or footling breech (when the baby’s feet are close to the cervix), our ‘O’ becomes an ‘S’ for sacrum (the backbone of the baby’s bottom).
When your baby isn’t head or bottom down, you might need intervention to successfully birth your baby. Your doctor will do an ultrasound scan to determine whether vaginal birth is possible.
Left occiput anterior vs posterior
Babies entering the pelvis in an anterior position (baby’s back towards the mother’s front from 10 to 2 o’clock) is considering the best position for birth.
When the baby is in a posterior position this has the potential to affect how labor unfolds. If the baby can’t rotate into an anterior position, forceps or a c-section might be needed.
You can read more about how position affects labor in 8 Signs Your Baby’s Position Is Affecting Labor.
Is left occiput anterior normal?
The LOA position is normal and it has long been believed to be the ideal fetal position for birth.
However, this hadn’t been properly researched until this study looked into whether LOA improves birth outcomes.
The research shows LOA isn’t associated with better outcomes than other positions; neither does it increase the likelihood of a spontaneous vaginal birth.
Why is left occiput anterior best?
It was believed LOA was the best position for baby to be in to start labor because, in the majority of women, the uterus is slightly larger on this side. Most babies feel more comfortable placing their backs in the bigger space.
As each woman is unique, so is each uterus. It’s also absolutely fine if the baby presents in the ROA position.
What is the best position for baby to be in for birth?
Any anterior position, whether left or right, is an ideal fetal position. The anterior positions make it easier for the baby’s head to navigate the birth canal.
When babies enter the pelvis in the left or right occiput posterior position women can feel more discomfort during labor.
During contractions, the fetal head presses on the mother’s spine instead of towards the front, where the cervix is. This is what women mean when they refer to ‘back labor’.
You might wonder how midwives determine a baby’s position when they perform a vaginal exam.
The baby’s skull has different individual bones that aren’t fixed like those in an adult skull.
The places where one bone meets another are called suture lines.
When more than two bones meet they have between them a hollow space called a fontanelle, to allow bone growth.
There are two fontanelles in the midline of the baby’s head. The anterior is diamond-shaped and the posterior is triangular.
Those landmarks help health care providers have a lot information at the tips of their fingers. Isn’t that amazing?
Find out more in What Happens To Your Baby’s Head During Birth?.
Left occiput anterior kicks
During pregnancy, when the baby is in the LOA position, his back and shoulders are on the left side of the woman’s belly, giving it a round, solid shape. This leaves all of the baby’s limbs towards his front, and the mother will feel more movement on her right side.
You can try to feel with your hands the position your baby is in inside your belly.
In this ‘belly mapping’, you’ll find the part that’s more solid, and where your belly gets its round-pregnancy shape, is where the baby’s back is.
Where you feel it’s more hollow, with a few small bumps, is where the baby’s little limbs are.
How can I keep my baby in anterior position?
After all we’ve learned about fetal position, one of the things you might be wondering is whether there are any techniques to make sure your baby is in an anterior position when labor starts.
Yes, there are many things you can do during pregnancy, and even during labor, to make sure the baby enters your pelvis facing towards your spine.
Have a look at our article about Optimal Fetal Positioning to find tips and techniques to make sure your baby stays in an optimal anterior position.