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KEY POINTS The direction and magnitude of forces affect the form of the developing fetus. Abnormal mechanical forces give rise to deformation in humans in much the same fashion as abnormal forces may deform a tree. The tissues of a human fetus are especially pliable and easily molded, especially as a fetus fills out the uterus in late gestation. Many factors can lead to an aberrant…

KEY POINTS Fetal vascular disruption defects refer to structural defects that occur after a structure has formed normally, and they are usually limited to tissues within a defined area that are supplied by the affected blood vessels. Decreased blood flow to the affected area leads to hypoxia, endothelial cell damage, hemorrhage, tissue loss, and repair. Defects attributed to vascular defects included amniotic band defects, terminal transverse…

KEY POINTS The underlying mechanism for most defects related to problems associated with failed first-trimester obstetric procedures is vascular disruption. With chorionic villus sampling, removal of villi may result in embryonic hypotension, hypoxia, endothelial damage, hemorrhage, and necrosis with tissue loss involving distal structures in the upper body (hands and tongue), with middle digital rays more affected than medial or lateral rays. Failed dilatation and uterine…

KEY POINTS Compression during early morphogenesis (the first trimester) can result in three types of defects: molded deformations, incomplete morphogenesis, and disruptions of morphogenesis. Experimental animal studies showed that early amniotic sac puncture caused defects similar to Pierre Robin sequence, cleft palate, syndactyly, and limb-reduction defects. Limb-body wall complex is a rare defect characterized by extensive extremity and body wall defects, often associated with low birth…

KEY POINTS Ectopic pregnancy occurs when a fertilized ovum implants outside the uterus, most commonly in the fallopian tube. Risk factors for ectopic pregnancy include tubal damage, prior ectopic pregnancy, use of intrauterine devices, tubal sterilization, infertility, pelvic inflammatory disease, genital infections, multiple sexual partners, endometriosis, and cigarette smoking. Abdominal pregnancies have a higher maternal mortality rate compared with tubal pregnancies and intrauterine pregnancies due to…

KEY POINTS Fetal movement is crucial for normal joint development, and lack of movement can lead to joint contractures. Prenatal diagnosis of fetal akinesia may reveal additional structural abnormalities such as cystic hygroma, increased nuchal translucency, and hydrops fetalis. Fetal akinesia deformation sequence (FADS) is a term used to describe the causally heterogeneous conditions characterized by fetal akinesia and associated malformations. Experimental studies in animals have…

KEY POINTS Amniotic fluid tends to decrease during the last trimester of pregnancy, and a serious deficiency can result in fetal constraint. Oligohydramnios may be caused by renal/urinary tract malformations or amniotic rupture, accompanied by constrictive amnion strands, which can lead to various birth defects. Renal oligohydramnios is predominantly caused by congenital abnormalities of the kidney and urogenital tract. Oligohydramnios is associated with poor placental function,…

KEY POINTS Various types of uterine malformations, such as bicornuate or myomatous uterus, can lead to small uterine cavity deformation, increasing the risk of fetal deformation and complications. Diagnostic procedures like hysterosalpingography, laparoscopy, and 3D ultrasonography are more accurate in identifying congenital uterine anomalies compared with hysterosalpingography alone. Different types of uterine anomalies are associated with specific reproductive outcomes, including increased rates of miscarriage, preterm birth,…

KEY POINTS Factors contributing to face presentation include fetal anomalies, contracted pelvis, fetopelvic disproportion, or cord around the neck. Face presentation is more common in large infants (>4000 g), small infants (<2300 g), and cephalopelvic disproportion. Cesarean section is considered if the fetus is large, the mother has a relatively small pelvis, or there is a persistent mentum posterior presentation with arrested descent. Manual conversion from…

KEY POINTS Transverse lie is the second most common nonvertex presentation during delivery, occurring in 1.2–3 per 100 deliveries. Multiparity, prematurity, placenta previa, polyhydramnios, uterine anomalies, and uterine myomas are associated with transverse lie. Laxity of abdominal musculature in multiparous women is considered the primary factor contributing to transverse lie in these women. Transverse lie can lead to facial flattening, limited mandibular growth, retroflexed head, prominent…

KEY POINTS Breech presentation is considered normal in premature fetuses before 32 weeks of gestation but is responsible for one-third of all deformations in term newborns. Factors leading to breech presentation include prematurity, twinning, chronic amniotic fluid leakage, uterine malformations, placenta previa, maternal hypertension, and fetal malformations. Primigravida women, especially older primigravida women, are more likely to have breech presentation due to uterine shape and limited…

KEY POINTS Wormian bones are accessory bones found within cranial suture lines that vary in size and quantity, with few and small bones being common and many large bones being extremely rare. A majority of children with an excessive number of Wormian bones have some abnormality of the central nervous system. They occur most commonly in the lambdoid sutures and within fontanels. Wormian bones are thought…

KEY POINTS Cephalohematoma is a subperiosteal extracranial hemorrhage often from an injury to the cranial periosteum during labor or a traumatic delivery. Risk factors include vacuum extraction, forceps delivery, fetal scalp monitors, instrumentation, and increased birth weight. Complications of cephalohematoma can include underlying skull fracture, anemia, hyperbilirubinemia, calcification, or infection. Cephalohematomas are usually localized and may resolve spontaneously within a few weeks or months. In rare…

KEY POINTS Aplasia cutis congenita (ACC) is a congenital absence of skin, most commonly affecting the scalp and characterized by raw areas that mature into atrophic scars devoid of hair. ACC can occur in isolation or associated with other abnormalities and malformations, such as spinal dysraphism, encephaloceles, epidermal nevus, or nevus sebaceous syndrome. The cause of ACC is heterogeneous and can include vascular disruption, infection, trauma,…