Pregnancy Flashcards
what is Early development of the human embryo is vulnerable to
teratogens- factors that can affect the details of development.
what complications can occur early
spina bifida and cleft palate occur in early stages of development.
when is spontaneous loss of pregnancy most common
during the first trimester is very common and
around 1/3 of all conceptions do not complete the first trimester
what is absolute limit of infant survival
the second trimester is the absolute limit of infant survival, without modern neonatal intensive care
22 weeks of pregnancy and 50% survival at about 25 weeks.
how long is first trimester
0-13 weeks
how long is second trimester
14-26
what gestational age is limit of viability
23 weeks
once limit of viability is passed what becomes a problem
early delivery (10%)
what causes early delivery
labour starting before term
deteriorating maternal or fetal health- growth restricted infants
and pre-eclamptic pregnancies.
define term time period
term covers 37-41 weeks of gestation
expected time of delivery is term (39-40 weeks)
what infants are at most risk and why
Infants born before 32 weeks GA
due to incomplete development of their lungs, digestive system, brain and immune system.
what are the main risks in the 3rd trimester
concerned with birth.
Risks associated with labour can be minimised by monitoring fetal health and
delivery by Caesarean section if that is indicated.
what time period is the 3rd trimester
27-39 weeks
what anatomical and physiological changes INCREASE in mother during pregnancy
weight hormone levels blood clotting tendency basal body temp breast size nausea and vomiting vaginal mucous production ALL INCREASE
WHAT decreases in mother
Decreased blood pressure
what other functions and states off the body are altered in the mother
Altered brain function/ appetite/ fluid balance and
urinary frequency/ emotional state/ joints/ immune system
what happens when the conceptus make contact with maternal tissue at week 4
As conceptus grows, it makes transient contact with maternal capillaries
rapidly proliferating cytotrophoblast cells form a shell around the conceptus
what do cut-trophoblast cells do to the conceptus wk4
isolates conceptus from maternal blood
what provides nutrients for the placenta and developing baby during first trimester
Decidual glands hypertrophy
how long does the cytotrophoblast shell last
Cytotrophoblast shell remains in place till about 10 weeks gestation, blocking the spiral arteries.
how do cytotrophoblast cells remodel the arteries
During weeks 10-12 gestation, the shell gradually breaks down
results in the spiral arteries providing maternal blood to the placenta
what provides nutrients following breakdown of cytotrophoblast shell
spiral arteries are main supply of nutrients to the developing placenta and fetus
give a specific cause of miscarriage in late first trimester
If the placenta is not fully anchored to the maternal decidua, the increase in pressure can detach the placenta leading to miscarriage
Remodelling of spiral arteries by cytotrophoblast cells begin and end
begins: 1st trimester
ends: 16-18 weeks gestation
(nutrient provision throughout trimester 2/3 the. growth is high)
why is spiral artery remodelling essential
it converts narrow arteries to wide-bore vessels that can transport large volumes of maternal blood- providing the quantities of nutrients needed
name another distinguishing feature of the remodelled arteries
There is also a lack of smooth muscle
list the main functions fo the placenta
Exchange of nutrients/waste between vascular systems
Connection
Seperation
biosynthesis - syntheti. active
Immunoregulation
describe the immunoregulatory function of the placenta
Interactions between placenta and maternal tissue ensures there is no rejection of the conceptus during pregnancy
how does the placenta connect and why is this vital
make strong connections with the underlying maternal decidua (uterine lining) to last for the 9 months of pregnancy.
Anchorage is essential as the placenta is in contact with maternal arterial blood.
describe how placenta develops during pregnancy
placenta develops from a simple layer of cells to a complex multifunctional tissue as pregnancy progresses.
what is the primary subunit of the placenta
placental villus which provides a large surface area for exchange between the maternal and fetal vascular systems
compare functions of the placenta and lungs
Placenta has a parallel function to the lungs for the fetus during pregnancy so
the arterial system= de-oxygenated blood;
venous system= oxygenated blood
Maternal surface of placenta sub-divided into…..
cotyledons, each containing one or more villi.
where does the placenta develop
in the underlying layer of the cytotrophoblast, adjacent to the embryo
describe how the placenta develops
Cytotrophoblast proliferates into the syncytium following implantation; first the cytotrophoblast column is formed which then undergoes branching. This branching process continues throughout pregnancy.
does the placental villus change throughout pregnancy
Overall structure of placental villus does not change throughout pregnancy but there are a few modifications
give an example of one of these modifications
For example, at term, there are fewer cytotrophoblast present which maxims the efficacy of nutrient transfer into the fetal blood, enhancing fetal growth in later pregnancy.
( closer apposition between the syncytium and the placental capillaries)
define still birth
Stillbirth= death of an infant within the uterus, so that it is delivered without any signs of life;
delivery after viability limit (23 weeks); potentially viable infants
what is still birth linked with
cases tend to be linked with labour, but some cases occur before delivery- complication of pregnancy
when can still birth occur
It can occur at any gestational age, including term.
define miscarriage
deliver before viability limit, non-viable infants
how can infant be assessed with during development
Doppler ultrasound
a decrease in, or lack of, foetal movement may indicate an increased risk of still birth
