Assoc. prof. Edyta Mądry Pregnancy

Pregnancy

Assoc. prof. Edyta Mądry

MD PhD

PREGNANCY

Edyta Mądry MD, PhD

Department of Physiology Medical University

Poznań

Pregnancy Definition

The period from conception to

birth.

Conception

• Conception means a woman's egg has been fertilized by a man's sperm.

⃰ Conception

• A secondary oocyte can be fertilized for about 24 hours after ovulation

• Sperm remain viable for up to 72 hours within the female reproductive tract

⃰ Fertilization

• Fertilization usually takes place in the outer one-third of the uterine tube (ampulla of oviduct), but can ocasionaly take place in the

abdominal cavity cervics of uterus (ectopic pregnancy)

• Sperm swim up the female reproductive tract, aided by muscular contractions of the uterus stimulated by prostaglandins in the

semen.

How does it start?

• Sperm reach ovum and cluster around it

⃰ Gestation

• Assumption:

Fertilized 14 days after the first day of LNMP

Gives birth 38 weeks after fertilization (+ or - 2 weeks)

Gestation in singleton pregnancies lasts an average of 40 weeks (280 days) from the first day of the last normalmenstrual period (LNMP).

10 lunar months = 9 calendar months = 280 days

(+ or – 2 weeks)

⃰ How to calculate the time of birth

Naegele's rule

1. Determine first day of LNMP 2. Add one year

3. Subtract three months 4. Add seven days

For example: first day of LNMP April 21st, 2015

Fertilization

o 1 Oocyte

o 300 Million Sperm

o 24 hours post ovulation

o size: 0.1 - 0.15 mm

When the sperm penetrates the egg, the egg immediately releases a chemicals creating a hard “shell”

around it to keep all other sperm out and prevent

polyspermy

Fertilization

Fertilization

• FERTILIZED EGG = ZYGOTE

• The fertilization process takes about 24 hours.

– It takes about ten hours to navigate the female productive track, moving up the vaginal canal, through the cervix, and into the fallopian tube where fertilization begins.

Cleavage

• First Cell Division,

• Mitotic division

• size 0.1 - 0.2 mm

• 1.5 - 3 days post-ovulation

4 cell zygote

2 cell zygote

The zygote begins to develop

Three to four days after fertilization.

• morula (mulberry shaped)- about 16 cells

• morula leaves the fallopian tube and enters the uterine cavity

16 cell morula

8 cell zygote

Early Blastocyst

• When zygote divides to 32 cells it becomes known as a blastocyst

• size 0.1 - 0.2 mm

• 4 days post-ovulation

• blastocyst formation

• Two cell types are forming:

– embryoblast (inner cell mass on the inside of the blastocele)

– trophoblast (the cells on the outside of the blastocele).

Implantation Begins

• Human Chorionic Gonadotropin (hCG) level rise

• 0.1 - 0.2 mm

• 5 - 6 days post-ovulation

• The trophoblast cells secretes an enzyme which erodes the epithelial

uterine lining and creates an implantation site for the blastocyst (see slide number 22)

Blastocyst

Uterine lining

The blastocyst

embeds into the uterine lining,

Implantation

• ovary continues producing progesterone

• trophoblast cells continue releasing human chorionic gonadotropin

(hCG)

• Endometrial glands in the uterus enlarge in response to the blastocyst and the implantation site becomes swollen with new capillaries ( see slaids 26 and 27).

Implantation

Implantation Completed

• Placental Circulation System Begins to form

• 0.1 - 0.2 mm

• 7 - 12 days post-ovulation

• Trophoblast cells engulf and destroy cells of the uterine lining creating blood pools, both stimulating new capillaries to grow and foretelling the growth of the

Implantation Completed

•The inner cell mass divides, rapidly forming a two-layered disc

•The top layer of cells will become the embryo and amniotic cavity

–The lower cells will become the yolk sac.

• ⃰ Inner cell mass forms two cavities:

– yolk sac

– amniotic cavity

• ⃰ In humans the yolk sac produces blood cells and future sex cells

• The amniotic cavity becomes the cavity in which the embryo floats.

• Fluid is produced from fetal urine, and secretions from the skin, respiratory tract, and amniotic

membranes.

Symptoms of early pregnancy

 Food cravings or aversions

 Smell sensitivity

 Heartburn

 Missed Period

 Morning Sickness

 Constipation

 Mood Swings/ Irritability

 Higher body temperature

 Low Back Pain

 Tender breast

 Bloating / Weight Gain

 Fatigue

Four Weeks

After the cluster of cells attaches to the womb it is called an embryo.

.

Day 22

Day 24

Day 26 Day 28

At the end of 4 weeks:

• Embryo is 1/4 inch in length

• Heart, digestive system, backbone and spinal cord begin to form

• Placenta (sometimes called "afterbirth") begins developing

At the end of 8 weeks:

•Embryo is 1 1/8 inches in length

•Eyes, nose, lips, tongue, ears and teeth are forming

At the end of 12 weeks:

Fetus is 2 1/2 to 3 inches long Weight is about 1/2 to 1 ounce Nails start to develop and

earlobes are formed

Arms, hands, fingers, legs, feet and toes are fully formed

Eyes are almost fully developed

By this stage, a fetus has developed most of his/her organs and tissues

At the end of 4 months:

•Fetus is 6 1/2 to 7 inches long

•Weight is about 6 to 7 ounces

•Fetus is developing reflexes such as sucking and swallowing.

•Fingers and toes are well defined

•Sex is identifiable

At the end of 5 months:

•Fetus is 8 to 10 inches long

•Weight is about 1 pound

•Hair begins to grow on his/her head

•Soft woolly hair called lanugo covers fetus body

Mother begins to feel fetal movement

At the end of 6 months:

•Fetus is 11 to 14 inches long

•Weight is about 1 3/4 to 2 pounds

•Eyelids begin to part and eyes open occasionally for short periods of

•At the end of 7 months:

•Fetus is 14 to 16 inches long

•Weight is about 2 1/2 to 3 1/2 Pounds

•Fat layers are forming

•If born at this time, he/she will be considered a premature baby

and require special care

At the end of 8 months:

•Fetus is 16 1/2 to 18 inches long

•Weight is about 4 to 6 pounds

•Overall growth is rapid this month

•Tremendous brain growth occurs

•Most body organs are now developed with the exception of the lungs

•Movements or "kicks" are strong enough to be visible from the outside

•

At the end of 9 months:

•Fetus is 19 to 20 inches long

•Weight is about 7 to 7 ½ pounds

•The lungs are mature

•Baby is now fully developed and can survive outside the mother's body

•He/she settles down lower in the abdomen in preparation for

birth and may seem less active

Labor (parturition)- Stage one

• the period from the onset of true labor contractions until the cervix is completely dilated at 10 cm.

• The uterine contractions cause the cervix to dilate, and the amniotic sac may rupture.

• Usually lasts 6 – 24 hours depending on the number of previous deliveries.

Stage 2

• Period from maximal cervical dilation until

the birth of the baby

• Lasts minutes to an hour

• Contractions become

• more intense and frequent.

Stage 3

• The expulsion of the placenta

• Usually occurs within 15 minutes after the birth of the baby, but can range from 5 to 60 minutes.

⃰ Placenta

• 10-12 weeks is the period of placenta formation

• Trophoblast cells use same molecular mechanisms as tumors, but are highly regulated and controlled

Placenta

• FETAL SIDE

• MATERNAL SIDE

• They provide…

– protection – nutrition – respiration – excretion

– hormone production

⃰ Functions of Placenta

• Exchange of gases between fetus and mother

• Delivery of nutrients from mother to fetus

• Delivery of antibodies from mother to fetus

• Removal of fetus waste

• Secretion of hormons including human chorionic gonadotropin ( hCG), progesterone, estrogen, and human chorinic

Placental barrier

• Maternal and fetal blood do

not mix- “placental barrier”

Metabolic Functions of the Placenta

• Glycogen synthesis and storage

• Cholesterol synthesis: placental cholesterol is

precursor for placental progesterone and estrogens

• Protein production

⃰ Endocrine Functions

• Placenta Produces Peptide hormones

– Human Chorionic gonodotrophin (hCG) - secreted early and helps to maintain synthesis of progesterone – Human placental lactogen (hPL): increase supply of

glucose to future by decreasing maternal stores of fatty acids by altering maternal secretion of insulin

– Insulin-like growth factors (IGF): IGF signaling system is a major regulator of growth in fetus and infant

⃰ Endocrine Functions

• Steroid hormones

– Progesterone: produced by placenta, needed to maintain non-contractile uterus

– Estrogen: produced by placenta drives many processes in pregnancy

An XY individual with androgen insensitivity syndrome.

Despite the XY karyotype ^{and the}

presence of testes, such individuals develop female secondary sex characteristics.

Internally, however, these women lack the Müllerian duct derivatives and have undescended testes. (Photograph courtesy of C. B. Hammond.)

How important are hormones ?

Sex differentiation

The ovary makes thecal cells and granulosa cells, which together are capable of synthesizing estrogen^.

Under the influence of estrogen (first from the mother, then from the fetal gonads), the

Müllerian duct differentiates into the female genitalia.

⃰ Female development

⃰ 3 hormones necessary for male development

1. Müllerian Inhibiting Substance (MIS) = anti-Müllerian duct factor (AMH), ^causes

the Müllerian duct to regress.

2.Testosterone, causes the differentiation of the Wolffian duct into the male internal genitalia.

In the urogenital region, testosterone is converted into

3. Dihydrotestosterone (DHT), that causes the

morphogenesis of the external genitali (penis) and prostate gland.

⃰

⃰ Hormones in pregnancy

⃰ Function of Human Chorionic Gonadotropin

• Prevent degeneration of the corpus luteum

• Stimulates the corpus luteum to secrete estrogen and progesteron

• Stimulates steroid synthesis in the developing fetal adrenals

• Stimulates fetal gonads, especially

testosteron production by the fetal testes.

• Suppresses maternal lymphocytes and

reduces the possibility of immunoreactions against the fetus.

⃰ What does progesterone do?

•It maintains the lining of the uterus which makes it possible for a fertilized egg to attach and survive

•Makes cervical mucous accessible by sperm

•Prevents immune rejection of the developing baby

•Increases libido around ovulation

•Protects against endometrial, breast, ovarian and prostrate cancer

•Normalizes blood clotting

Please note!

⃰ ^The information marked with a red star are the most important in the process of preparing up for the final exam.