Chapter 24. Abnormal fetal lie and presentation

24.1. ABNORMAL FETAL LIE

ICD-10 code

• O32.2 Maternal care for oblique or transverse lie.

Abnormal fetal lie is seen in 0.2-0.7% of all deliveries, in secundiparas it occurs ten times more often than in primiparas. Oblique and transverse lie are regarded as abnormal. In abnormal lie the long axis of the fetus crosses the long axis of the uterus at an angle.

• In a transverse lie the long axis of the fetus crosses the uterine long axis at a right angle while large fetal parts are above the iliac crests (Fig. 24.1).

Fig. 24.1. Transverse fetal lie. First anterior position

• In an oblique lie the long axis of the fetus crosses the uterine axis at an acute angle while one of large fetal parts is in one of iliac fossas of the greater pelvis. Oblique lie is in most cases transient (unstable): during labor it changes to transverse or longitudinal lie (Fig. 24.2).

Fetal position in transverse or oblique lie is determined by the fetal head: if it is on the left, the fetus is in the first position, if it is on the right, it is the second position.

Fig. 24.2. Oblique fetal lie. First anterior position

If the fetal back faces forward, this is an anterior position, if it faces backward, this is a posterior position (Latin, visus).

24.1.1. Etiology

Causes of abnormal fetal lie:

• decreased uterine tone;

• incompetence of abdominal muscles;

• discrepancy of the uterine cavity shape (like in uterine myoma) and fetal size (Fig. 24.3);

Fig. 24.3. Pregnancy and bicornuate uterus (left), uterine myoma (right)

• multiple pregnancy;

• polyhydramnios;

• premature fetus;

• developmental disorder and uterine tumor;

• placenta previa;

• contracted pelvis;

• fetal malformations (hydrocephalus, anencephaly);