Maternal Recognition of Pregnancy: Signals, Hormones, and Species Differences

What is maternal recognition of pregnancy?

The process where the conceptus signals its presence to the dam, allowing physiological changes to maintain pregnancy.

What is the key outcome of maternal recognition of pregnancy?

Maintenance of progesterone, usually by maintaining corpus luteum (CL) function or replacing luteal progesterone with placental progesterone.

What is an embryo?

The developing offspring in the early stages after fertilization.

What are extraembryonic membranes?

Fetal membranes that support the embryo/fetus, including structures involved in attachment, nutrient exchange, and fluid compartments.

Define conceptus.

The embryo/fetus plus the associated extraembryonic membranes.

What is a luteotropic signal?

A signal that directly supports or stimulates corpus luteum (CL) function and progesterone production.

What is an antiluteolytic signal?

A signal that prevents luteolysis, usually by blocking or reducing uterine PGF2 alpha pulses.

How do ruminants recognize pregnancy?

Through interferon-tau (IFN-tau) which blocks oxytocin receptor expression and PGF2 alpha release.

What role does estrogen play in pig pregnancy recognition?

Estrogen redirects PGF2 alpha secretion, preventing luteolysis and maintaining CL progesterone.

What is the significance of eCG in mares?

eCG from endometrial cups stimulates accessory CL formation and provides additional progesterone support.

What happens in a non-pregnant cycle?

Oxytocin stimulates PGF2 alpha release, leading to luteolysis and a fall in progesterone, resulting in return to estrus.

What is the role of hCG in human pregnancy?

hCG maintains the corpus luteum (CL) until the placenta can produce sufficient progesterone.

What are the progesterone requirements for a sow during gestation?

The corpus luteum (CL) is required throughout gestation; the placenta never takes over progesterone production.

How long does the CL support pregnancy in cows?

The CL supports pregnancy for the first 128 days, after which the placenta takes over.

What is the role of aromatase in pregnancy recognition in pigs?

Aromatase is needed to make estrogens; its knockout showed that conceptus estrogen is not essential for early pregnancy maintenance but is critical after 30 days.

What is the function of PGF2 alpha?

PGF2 alpha causes luteolysis, leading to a decrease in progesterone levels.

What is the role of oxytocin in the reproductive cycle?

Oxytocin stimulates PGF2 alpha release, which can lead to luteolysis if pregnancy is not established.

What is the importance of vascularization in maternal recognition of pregnancy?

Increased vascularization of the endometrium supports conceptus growth by enhancing nutrient and oxygen supply.

What is histotroph?

Also known as 'uterine milk', it is produced to support the growing conceptus.

What happens to the conceptus in mares around day 18?

The conceptus migrates throughout the uterus, and its capsule shrinks and disappears by days 21-23.

How does the conceptus signal its presence in pigs?

The conceptus produces estrogen, which redirects PGF2 alpha secretion to prevent luteolysis.

What is the role of the placenta in pregnancy maintenance for ewes?

The placenta supports pregnancy for the last 100 days after the initial 40 days supported by the CL.