**10. Placenta, umbilical cord**

The placenta is the organ that connects the mother to the fetus and ensures the normal development and growth of the fetus. It is important to examine the location (especially the relative position to the cervix) and morphology of the placenta [55].

Placenta praevia is an anomaly when the placenta is inserted either partially or totally in the lower, passive segment of the uterus. It can only be diagnosed after the second trimester because the site of insertion usually shifts upwards with the growth of the uterus. Placenta praevia has a birth prevalence of 2.8:1000 and it is more common in twin pregnancies and after a previous cesarean section [56, 57].

When the placenta is abnormally attached, it may reach the myometrium (placenta accreta), the serosa (placenta increta) or other organs (placenta percreta). The detection of placenta accreta is hard, but increta and percreta are easier to visualize. The birth prevalence of placenta accreta is 1:2500, while in placenta praevia cases, the prevalence is 1:10 [56, 57].

The maturity of the placenta was classified by Grannum in 1988 based on the ultrasound image:


When the maturity of the placenta and the fetal biometry are discordant, it suggests intrauterine growth retardation [55, 57, 58].

Examination of the insertion site of the umbilical cord is also important as it provides the nutrient supply going to the fetus. Marginal insertion is often associated with intrauterine growth retardation. In case of velamentous cord insertion, the umbilical vessels are only covered by the amniotic membrane, therefore they are less protected. Also, this anomaly is often associated with the presence of a single umbilical artery [57]. Single umbilical artery is present in 0.2–1% of the pregnancies. It is a minor anomaly that is often associated with cardiovascular, brain and urogenital malformations and Trisomy 13 or 18 [57, 58].

Normally, the umbilical cord is 50 cm long at terminus. When it is shorter than 30 cm, it is classified as short, while a long umbilical cord is over 80 cm. The length of the cord affects the mobility of the fetus, therefore it is important to examine this feature. Furthermore, the degree of coiling of the umbilical cord should be determined (CI: coiling index) as the absence of coiling may suggest chromosomal abnormality, fetal distress or retardation [57, 58].
