Physiology of Pregnancy

Question 1

what happens if an embryo is lost prior to maternal recognition of pregnancy?

Answer 1

• CL regresses at normal time
• no delay in return to estrus

Question 2

what happens if an embryo is lost after maternal recognition of pregnancy?

Answer 2

• CL persists
• delay in return to estrus
• need to administer prostaglandins to lyse CL and allow for a return to estrus

Question 3

what should you administer if an embeyo is lost after maternal recognition of pregnancy?

Answer 3

prostaglandins to lyse CL and allow for return to estrus

Question 4

what are causes of early pregnancy loss?

Answer 4

Maternal Age
◦ Older oocytes; DNA damage over time
 Endometrial/Uterine Disease
 Progesterone Insufficiency
 Chromosomal Abnormalities
 Miscellaneous
◦ Inadequate nutrition
◦ Maternal stress
◦ Early postpartum pregnancies (some species) ◦ Abnormalities of embryonic development

Question 5

describe placenta vs fetal membranes

Answer 5

placenta = consists of both maternal and embryonic/fetal components
fetal membranes = describe only the fetal component

Question 6

what gives nutritional support to the embryo in early pregnancy?

Answer 6

• secretions from endometrial glands, micronutrients get taken up by trophoblast cells and eventually by vascularized yolk sac
• “histotrophic support”

Question 7

what gives nutritional support to the embryo in late pregnancy?

Answer 7

• development of close association between vascular tissue of maternal endometrium and fetal membranes allows for “hemotrophic support”

Question 8

when does implantation/attachment of placental tissue with endometrium occur in major species?

Answer 8

pigs: 14-18 days
sheep: 15-18 days
cows: 18-22 days
horses: 35-38 days

Question 9

when do you see a heartbeat in dog/cow/horse?

Answer 9

day 25

Question 10

what membrane is visible on the outside first of the fetus?

Answer 10

amnion, fetus is within that

Question 11

what species have diffuse placentas?

Answer 11

horses, pigs
microcotyledons spread like villi covering entire surface of placenta. everything covered

Question 12

what species have cotyledonary placentas?

Answer 12

ruminants: discrete attachment sites between cotyledons (placenta) and caruncles (uterus) forming placentomes
cow: external eruption where things attach
sheep: lil sulcus/depression of attachment

Question 13

what species have zonary placentas?

Answer 13

carnivores: contact between placenta and endometrium is in a band around fetus. ring surrounding one area. no attachment other places except that complete attachment in the cylindrical zone

Question 14

what type of placenta do large animals have?

Answer 14

epitheliochorial
- 6 layers of separation
- doesn’t allow for any transfer of antibodies to fetus = colostrum important!!

Question 15

what are the 6 layers of epitheliochorial placenta?

Answer 15

• fetal endothelial cells
• fetal connective tissue
• chorionic epithelial cells
• endometrial epithelial cells
• maternal connective tissue
• maternal endothelial cells

Question 16

what type of placenta do dogs and cats have/

Answer 16

endotheliochorial
4 layers of separation
chorionic villi in contact with endothelium of maternal blood vessels
colostrum still important, but allows for moderate antibody transfer

Question 17

what type of placenta do humans and rodents have?

Answer 17

hemochorial
fetal chorion comes in contact with maternal blood
only 3 layers of separation = allows for significant transplacental transfer of immunoglobulins

Question 18

what species are CL dependent for their source of progesterone throughout pregnancy?

Answer 18

dogs, cats, goats!! pigs, llamas, alpacas

Question 19

what species are not CL dependent?

Answer 19

cows, sheep, horses
cow placenta makes some progesterone around 70 days, ovaries not needed anymore

Question 20

what is the difference between goats and sheep dependency on CL?

Answer 20

goats are so CL dependent; sniffing a bottle of prostaglandins would make them lose their pregnancy because they are so CL dependent

sheep are not CL dependent

Question 21

endometrial cups are unique to what species?

Answer 21

horses: make eCG. FSH biological activity

Question 22

what are equine endometrial cups?

Answer 22

• specialized trophoblast cells
• origin is chorionic girdle: visible by day 25 of gestation
• form distinct “cup” shape aggregations of fetal tissue within maternal endometrium
• makes eCG

Question 23

what is so useful about equine endometrial cups?

Answer 23

• produce eCG: equine chorionic gonadotropin. may provide protection from maternal immune system
• eCG has both LH and FSH biological activity, but has FSH bioactivity when administered to other species
• eCG used clinically to cause superovulation

Question 24

what does endogenous FSH stimulate in the mare?

Answer 24

follicle development

Question 25

what does eCG cause?

Answer 25

ovulation and/or luteinization of the large follicles **secondary or accessory corpora lutea form**: produces additional progesterone, which helps support early pregnancy

Question 26

when do equine endometerial cups typically regress by?

Answer 26

day 120-150

Question 27

if there is pregnancy loss after day ________ in gestation, then endometrial cups will remain present

Answer 27

day 35: if still pregnant at day 35, endometrial cups form!! if pregnancy loss after day 35, then endometrial cups have invaded into uterus but those cups will still be there and mare will NOT cycle back for the rest of the year!!

Question 28

equine fetal gonads undergo dramatic enlargement and regression during what months of gestation?

Answer 28

3-8 months of gestation peaks at 7 months, don't really know why they do this. gonads make a lot of androgens! testosterone peaks in blood around 200 days of pregnancy, then gonads shrink and are born

Question 29

why might mares start showing male like behavior during pregnancy?

Answer 29

- fetal gonads enlarge around 7 months of gestation, and gonads make a lot of testosterone!! testosterone is a steroid and can cross the placenta and gets into bloodstream. makes mom have stallion-like behavior- this is normal for every mare - androgens are converted to estrogens by placental aromatase - gets high testosterone levels around 7 months of pregnancy

Question 30

what is the trouble with equine twins?

Answer 30

- abortion rate high - most mares cannot carry twins to term - abortion after 7 months from placental insufficiency - retained placenta, dystocia, ruptured prepubic tendon, rebreeding problems are all possible

Question 31

what are management options for mares with twins?

Answer 31

- let mare try to carry both- BAD DONT DO THIS - abort both- not happy client - eliminate one embryo: pregnancy reduction. most common. some mares naturally ovulate more than 1 follicle, and on day 14 of exam need to look for 2 embryos

Question 32

how does pregnancy reduction work in mares?

Answer 32

- optimal time period is day 14-16 - embryos migrate thru uterus from day 6-16 at which time they "fix" in position - reduction is when one embryonic vesicle is disrupted and the other is allowed to continue to develop - push ultrasound probe down on one embryonic vesicle

Question 33

management keys of twin possibilities in mares

Answer 33

- evaluate for multiple ovulations in mare - thorough ultrasound examination at 14 days - accurate detection and early intervention at detection time - twins are not always in 2 distinct embryonic vesicles or separated. need to separate them and reduce one. if twins are in 1 embryonic sac, they cannot be separated and will not survive