**3. Risk factors**

The risk factors can be classified according to the pre- pathogenic period of the natural history of the disease, in agent, host and environment; those of the environment can be classified in microenvironment, Environment maternal and macroenvironment.

#### **3.1 Agent**

### *3.1.1 Maternal hormones*

Relaxin is a pregnancy hormone, 6-kDa polypeptide, which increases the secretion of collagenase and activator of plasminogen, involved in collagenolysis [16]. It has been suggested that ligamentous hyperlaxity is a risk factor and that its potential to develop DC is increased due to maternal hormones such as relaxin, which are prepared prenatally to the mother's ligaments at the time of delivery [17] and cause a decrease in resistance. to the traction [11].

There are two hypotheses in relation to relaxin and DDH:

*Diagnosis of Developmental Dysplasia of the Hip in Newborns and Infants DOI: http://dx.doi.org/10.5772/intechopen.104085*


#### **3.2 Host**

#### *3.2.1 Heritage*

It is considered that there is influence of multifactorial inheritance, combining genetics and environmental conditions; 20% of cases have a family history, 6% if one of the parents was affected, 12% if it was one of the parents and a brother and 37% in monozygotic twins. Up to 20% of these cases have been associated with congenital malformations, such as clubfoot, amniotic bands of the pelvic limbs and congenital muscular torticollis [17]. Ömeroğlu et al., reported in a retrospective study, that there was an association of having a family history of CD with presenting DDH compared with infants who did not have DDH (P = .02, OR = 2.10) [23], although Mendoza et al., in Mexican neonates, found no statistical association between family history of DDHC and DDH in the neonate (P = .73, OR = 0.83) [24].

### *3.2.2 Position in utero*

The breech presentation, especially with the pelvic extremities in extension and adduction, have been indicated as risk factors for DC as well as for hip dislocation since it occurs in 30–50% of cases [10]. Ömeroğlu et al., Reported that breech presentation is associated with DC (P = .015, OR = 1.87) [23]. In the study of Mexican children, a strong statistical association was reported between breech presentation and DC (P =, 004, OR = 5.32] [24].

### *3.2.3 Firstborn*

Being the first child, the uterine force will be greater, being able to exert greater tension to the product [17]. Ömeroğlu et al., studied the relationship with female first-born and DDH; they did not find no association with DDH [23].

#### *3.2.4 Ethnicity*

It is considered that the frequency of DC in white race is of 50: 1 compared with African race; it is more frequent among American Indians and Eskimos than in South American or African Indians [11]. Eskimos and American Indians overdress children with legs in extension and adduction or move them in wooden strollers with narrow space; The Huichols in Mexico transport their babies in their body by hanging their limbs in abduction [11]. Highest incidence were reported from Finland, Croatia and Canada (5–195 per 1000), with very low incidences among populations in sub-Saharan Africa and Hong Kong (0–0.1 per 1000) [25]. Geographical and cultural factors regarding climate differences and the practice of swaddling respectively may in part explain this variation [26, 27].
