The Obstetric Diagnosis

The ultimate goal of obstetric case taking is to reach the obstetric diagnosis. The items of obstetric diagnosis includes the following in sequence:

• Gravidity

Gravidity is the number of pregnancy. It includes the current pregnancy and all other conditions; abnormal pregnancies such as molar and ectopic pregnacies regardless of the outcome; whether delivery or abortion. 

• Parity

Parity is the number of delivery. It includes all of the termination of pregnancies beyond 20 gestational weeks regardless of the fetal outcome; whether living or dead, single or multiple.

• Duration of current pregnancy

It is calculated in weeks using different methods: Naegele's formula and other clinical methods.

• Fetal lie

It is the relationship between the longitudinal axis of the fetus to the longitudinal axis of its mother. 

There are 3 types:  

  

[1] Longitudinal lie          [2] Transverse lie           [3] Oblique  lie

• Fetal presentation

It is the part of the fetus that presents to the pelvic inlet. It is first felt during vaginal examination (PV). There are 3 basics presentation of the fetus which are cephalic (vertex) in 96% of cases, breech in 3.5% of cases and shoulder in 0.5% of cases.

There are 2 theories to explain the high incidence of vertex presentation by adaptation and gravitational theory. In adaptation theory, the fetus more adapted to pyriform-shaped uterus with the larger buttock in the wider fundus and the smaller head in the narrow lower part of the uterus.

The fetal presentation may be determine by denominator. 

Denominator is the bony landmark of the presenting part. There are 4 main bone parts to determine the type of fetal presentation which are; chin (face), occiput (vertex), sacrum (breech) and scapula (shoulder). 

• Fetal position

It is the relation of the fetal back to the anterior abdominal wall of the mother. The fetal back may be antriorly/posteriorly/to the right/to the left of the mother. 

The 4 standard positions are left anterior (LA), right anterior (RA), right posterior (RP) or left posterior (LP) in sequence. The occiput (O), mentum/chin (M) and sacrum (S) which are the denominator is important to determine the fetal back position in relation to the mother. All of these bones is directly in relation to the back of the fetus except the chin.

Occipito-anterior positions are more common than occipito-posterior positions because in occipito-anterior positions the concavity of the anterior aspect of the fetus due to flexion fits with the convexcity of the vertebral column of the mother due to its lumbar lordosis.

In each presentation, except the shoulder, there are 8 positions. In vertex presentation they are: 

- Left occipito-anterior (LOA) 60% 

- Right occipito-anterior (ROA) 20%  

- Right occipito-posterior (ROP) 15%  

- Left occipito-posterior (LOP) 5%  

- Left occipito-transverse (LOT)  

- Right occipito-transverse (ROT)  

- Direct occipito-anterior (DOA/OA)  

- Direct occipito-posterior (DOP/OP)

• Fetal engagement

It means passage of the widest transverse diameter of the presenting part through the plane of the pelvic inlet. The widest transverse diameter of the fetal head is the bi-parietal diameter. The distance between both parietal eminances = 9.5 cm. It is the transverse engaging diameter in all cephalic presentation. 

However each cephalic presentation has its own longitudinal engaging diameter according to the attitude of the fetal head (Fetal habitus).

Fetal Habitus is the relation of fetal parts to each other. In majority of cases, the fetus is in the generalized flexion. Some other presentation is extension in face of the fetus.

Synclitism is the 2 parietal bones at the same level. The sagital suture of the fetus is in the midway from symphysis pubis to the promontary of sacrum.

[1] synclitism                   [2] Posterior asynclitism             [3] Anterior asynclitism

Asynclitism is lateral inclination to the frontal head, 2 parietal bones are not at the same level. It is divided into anterior and posterior asynclitism. Anterior asynclitism is more favorable because of less resistance only need to pass promontary of sacrum, less pressure on lower uterine segment and more in axis to the pelvic inlet.

• Complication of current pregnancy

For example; pre-eclampsia, ante-partum haemorrhage, premature rupture of fetal membranes, fetal malformation, fetal death and Rh-iso-immunization.

• Previous disease or cesarean section 

For example; maternal cardiac disease, diabetes mellitus, uterine anomalies or fibroids, and previous uterine scar.

So, from the points above, the example of obstetrics diagnosis may be:

"4th gravida, 2nd para, pregnant 36 weeks, longitudinal lie, cephalic presentation, left anterior position, non egaged head, rheumatic heart disease, previous cesarean section."