Maternal Environment and the Placenta
Remember, that most maternal disease do not affect the fetus.
Ways the maternal disease affects the fetus
1) transplacental disease – ex. Rubella
2) premature labor induction
3) altered fetal physiology – ex. Maternal Diabetes Mellitus
4) interference with fetal resp. or nutrition – Maternal HTN
5) Nutritional Status of the momma
Infection Effects on fetus Incidence
Rubella Abortion; Malformations high during 1st trimester
Herpes Simplex Viremia Rare
Coxsackie Myocarditis Low
Hepatitis Abortion; prematurity Low
Cytomegalovirus Infection 1-8/1000
Syphilis Infection 38-50%
Maternal Nutrition
Malnutrition Prematurity, maternal toxemia
Obesity Think big babies (5-10% over 4500g) and birth injuries
Endocrine Disorders
Diabetes Mellitus Inc. size, Inc. # of 20-30% perinatal mortality
congenital malformations 20-40% morbidity
Hyperthyroidism abortion and perinatal mortality 24% fetal loss
20% morbidity
Hematologic Disorders
Hypochromic Anemia Prematurity Common
Sickle Cell Prematurity, Growth Retardation 30-40% fetal or neonatal loss
ITP Passive transfer of platelet agglutinins Rare
Abortion
Ø 20Weeks gestation – split between spontaneous abortion & stillbirth
Ø Causes of early abortion
1) 40-50% is due to chromosome anomalies
2) Infection
3) Cytotoxic agents
4) Unknown (most)
5) Maternal causes
6) External trauma
Stillbirths or Fetal deaths
Ø Causes of Antepartum fetal death (80% of fetal deaths)
1) Fetal Disease
a. intrauterine sepsis
b. Lethal anomalies
c. Unknown
2) Placental Disease
3) Umbilical Cord lesions
4) Maternal Disease
5) Abnormal Circulation
6) Placental metastasis from maternal tumor, melanoma, lymphoma
7) Chronic underperfusion
a. growth retardation
b. thymus atrophies
c. abnormal bone maturation
Ø Causes of Intrapartum fetal death (20% of fetal deaths)
1) abnormal fetal position
2) cephalopelvic disproportion
3) Placental problems
a. prolapsed cord
b. placenta previa
c. abruptio placentae
4) Acute asphyxia
a. visceral congestion
b. aspiration of amniotic sac content
c. petechia in skin and viscera
The influence of placental lesions on the newborn infant
Normal Placental Morphology
- Fetal Component
Ø Remember that in the placenta arteries always cross over veins
Ø Three layers
1) Cytotrophoblast: mononuclear inner layer; has capacity to divide
2) Synctiotrophoblast; multinucleated outer layer
3) Intermediate trophoblast: form placental septae
Ø Membranes
1) Amnion: the inner epithelium -lined membrane
2) Chorion: The outer membrane, devoid of epithelium
Ø REMEMBER THAT THE UMBILICAL CORD HAS 2 ARTERIES and 1 VEIN.
- Maternal Component
Ø Intervillous space: contains maternal blood
Ø Decidua basalis: endometrium beneath the villi
Ø No maternal blood vessels in the placenta
Ø Villous is the structural unit of the placenta
- Normal Implantation
Ø Trophoblast invades the decidua basalis
Structural Abnormalities
Ø Remember, the closer the defect or abnormality is to the mother, the more worse it is.
Abnormal Implantation
- placenta previa – placenta located in the lower uterine segment, so that it partially or completely covers or adjoins the internal os
- placenta accreta – placenta abnormally adherent to the myometrium, with partial or complete absence of the decidua basalis
Abnormal Separation of a normally implanted placenta
- abruptio placentae – premature detachment of the placenta; hemorrhaging can endanger both the baby and the mother
Abnormal placental configuration
- accessory or subccenturiate lobes = bilobate placenta
- Fenestrated placenta – focal absence of placental villi
Abnormalities of the umbilical cord
- True knot – uncommon, long cords, twins
- False knot – functionally insignificant twists
- Marginal insertion (Battledore) – incidence 1/6 placentas; usu. No problem
- Velamentous insertion – inserts into the membranes, problem is hazard of bleeding at delivery; 1/100
- Single umbilical artery – 1/100; 25-50% have congenital malformations
Membrane Abnormalities
- Placenta extrachorialis – can be circummarginate(no ridge) or circumvallate (ridge); membranes insert on the fetal surface rather than on the margins; assoc. with IUGR
- Amnion nodosum – squamous cell aggregates on the amniotic surface derived from the vernix caseosa on the fetal skin; assoc. w/ oligohydraminios (implying leak of amnoitic fluid or diminished fetal urine flow)
- Amniotic bands – fragments of the membrane adhere to the fetus and cause abnormal development or amputation
- Premature rupture of membranes – maternal and fetal infection
Placental Thrombosis, Hemorrhage, and Infarction
- Thrombi and infarcts are universally present at term
- IUGR – may accompany infarction of 15-20% or more of the placenta
- Retroperitoneal hematoma – may inhibit placental circulation
- Infarcts: vascular occlusion or excess
- Thrombi: may be subchorionic or intervillous
Placental Infections
Portal of Entry
- ascending or hematogenous
Generic Anatomic Findings
- Chorionamnionitis: usually from ascending infection
- Villitis: usually from transplacental infection; can cause IUGR or can be normal.
- Funisitis: inflammation of the umbilical cord
Specific Placental Infection
- TORCH: Toxoplasmosis, rubella, CMV, Herpes
- CMV – most common, remember that they have intranuclear inclusions in the villi
- Syphilis – large placenta, plasma cell infiltrate, endovasculitis, spirochetes
- Others: malaria, listeria, other bacteria
Maternal Disorders and the Placenta
Pre-eclampsia (HTN, edema, and proteinuria) and Essential Hypertension
- can result in placental infarction
- synctiotrophoblast proliferation
- thickened basement membrane
- fibrinoid necrosis of decidua vessels
- IUGR
Diabetes Mellitus
- Exagerated findings that are normal in a term placenta
- Large fetus
- Large placenta with many infarcts and calcification
- Polyhydramnios may occur
Multiple Births and the abnormalities that are associated with them:
Placental Configurations
Monoamniotic/Monochorionic (MoMo) all are monozygotic (identical)
Diamniotic/Monochorionic (DiMo) all are monozygotic
Diamniotic/Dichorionic (DiDi) ½ are monozygotic; 2/3 are dizygotic
Ø If the babies are Identical (monozygotic), the placenta may be MoMo, DiMo, DiDi.
Ø If the babies are fraternal, the placenta has to be DiDi (sometimes the chorions can be fused)
Ø Twin Tranfusion Syndrome – due to unbalanced placental vascular anastomoses; one twin may end up a donor and the other a recipient; can lead to mortality in both
Ø Fetus papyraceous – a retained, macerated, or mummified twin.
Tags: abortion, Abruptio placentae, Acute asphyxia, Coxsackie, Cytomegalovirus, Cytotoxic agents, Cytotrophoblast, Diabetes mellitus, Fenestrated placenta, Fetal deaths, Hepatitis, Herpes Simplex, Hypochromic Anemia, intrauterine sepsis, Maternal Diabetes Mellitus, placenta accreta, Placenta extrachorialis, placenta previa, Placental metastasis, rubella syndrome, Sickle Cell, Synctiotrophoblast, syphilis, toxoplasmosis, transplacental disease, Umbilical Cord lesions, underperfusion
