''Pelvis justo major'' (also called giant pelvis) is a rare condition of the adult female

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

where the pelvis flares above the

iliopectineal line The iliopectineal line is the border of the iliopubic eminence. It can be defined as a compound structure of the arcuate line (from the ilium) and pectineal line (from the pubis). With the sacral promontory, it makes up the linea terminalis T ...

. It is 1.5 or more times larger than an average pelvis in every direction and is typically at least 42 cm (16.5 inches) in

biiliac width The ilium () (: ilia) is the uppermost and largest region of the coxal bone, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, with the exception of some snake species whi ...

. Even though this condition is classified as a

congenital abnormality A birth defect is an abnormal condition that is present at birth, regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth de ...

, it is not normally considered a medical disease of the pelvis as it typically holds a true gynecoid shape, only larger, without posing other major health risks except in childbirth. Pregnant women with this condition, at the time of delivery, may have a precipitous birth. With a wider pelvis justo major, there is no pelvic bone "molding" of the fetal head as is typical for a normally sized pelvis, and as such there is virtually no resistance from the pelvis itself. As this allows for a much more rapid vaginal birth, there is an increased risk of tearing of the perineal soft tissues. At the time of delivery, the strong

uterine The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic and fetal development of one or more fertilized eggs until bir ...

contractions and maternal bearing down almost instantly overwhelm the integrity of a previously unstreched vaginal orifice. This is often the case if the women have not previously practiced vaginal stretching to the degree that allows such an instant birthing, especially so for a

primiparous In biology and medicine, gravidity and parity are the number of times a female has been pregnant (gravidity) and carried the pregnancies to a viable gestational age (parity). These two terms are usually coupled, sometimes with additional terms, t ...

woman. This sudden or "instant delivery" problem leads many

OBGYN Obstetrics and gynaecology (also spelled as obstetrics and gynecology; abbreviated as Obst and Gynae, O&G, OB-GYN and OB/GYN) is the medical specialty that encompasses the two subspecialties of obstetrics (covering pregnancy, childbirth, and t ...

doctors to stress the importance of women with a larger pelvis, especially those with ''Pelvis justo major'', practicing pre-delivery vaginal stretching to avoid perineal injury. ''Pelvis justo major'' is present in less than one in one thousand adult women, and a measurement scan or

anthropometry Anthropometry (, ) refers to the measurement of the human individual. An early tool of biological anthropology, physical anthropology, it has been used for identification, for the purposes of understanding human physical variation, in paleoanthr ...

by calipers is required to diagnose the condition. The incidence of ''pelvis justo major'' pelvis is not found to be a strictly standard deviation type variation, as it follows a tail-skewed deviation to the right. ''Pelvis justo major'' is classified as congenital and thought to be partially inherited, especially from the maternal side.

References

{{Reflist Pelvis