PREGNANCY AND DEVELOPMENT

Mr. Chapman Science 9

Conception

Conception is when sperm and egg meet and fertilization occurs.

Conception occurs in the outer third of the fallopian tube. The fertilized egg is called a zygote.

Recall that the sperm can live inside a woman’s body for 2 to 7 days.

Signs of Pregnancy

Presumptive signs: nausea, vomiting, fatigue, frequent urination

Probable sings: positive pregnancy test, physical changes in the uterus

Positive signs: Ultrasound or X-ray of fetus, fetal heartbeat, fetal movement.

Development of the Fetus

Nine months of pregnancy are divided into three equal periods of three months – called trimesters.

First trimester – months 1 to 3 Second trimester – months 4 to 6 Third trimester – months 7 to 9

The Embryo and Its Support Systems

Placenta – an organ formed on the wall of the uterus through which the fetus receives oxygen and nutrients and gets rid of waste products

Human chorionic gonadotropin – a hormone secreted by the placenta; it is the substance detected in pregnancy tests.

Umbilical cord – the tube that connects the fetus to the placenta

Amniotic fluid – the watery fluid surrounding a developing fetus in the uterus.

From first trimester to birth

Fetal Development

First Trimester

Develops into a fetus with most of the major organ systems present

4th to 8th week – external body parts develop

During 7th week: liver, lungs, pancreas, kidneys, and intestines have formed and begun limited functioning.

End of 12th week – 10 centimetres long; weighs 19 grams

Second Trimester

Quickening occurs – women become aware of fetal movements (this occurs around the end of the 14th week.

Fetal heart beat can be detected.

Fetus opens its eyes.

Third Trimester

Fetus’ skin is wrinkled and covered with downlike hair.

Fetus turns in uterus to assume a head-down position.

Fetus experiences rapid growth.

Nutrition During Pregnancy

Diet during pregnancy is extremely important.

Woman must get enough protein, folic acid, calcium, magnesium, and vitamin A.

The fetus comes first – it draws the nutrients it needs first, and whatever is left after that is for mom.

Dangers of Malnutrition

Missing Calcium – future risk of bone and tooth loss

Missing folic acid (folate) – much higher risk of neural tube defects (proper amounts decrease risk by 50%)

Missing zinc – malformations of the central nervous system.

Effects of Drugs Taken During Pregnancy

Antibiotics – may damage the fetus

Alcohol – may cause fetal alcohol syndrome

Cocaine – increased risk of premature birth

Steroids – can cause masculinisation of a female fetus and other fetal damages.

Dads & drugs – can damage sperm and their genetic content

Premature Babies – “Preemies” There are all kinds of risks associated

with babies being born too early. Any baby who is born before the 37th week of gestation is considered premature.

Recall that a normal gestation period is 40 weeks. However, it is often considered normal to be anywhere from 37 – 42 weeks.

Risks for Preemies

Immature Lungs – the lungs of some babies are not able to function fully on their own if born prematurely. Sometimes, steroids are given to these babies to attempt to force their lungs to develop faster. This is often successful.

Pneumonia – this is an infection in the lungs where gas exchange normally occurs. This prevents anyone with pneumonia from getting enough oxygen in their blood.

Risks for Preemies

Infections – the immune systems of many babies are not ready to handle the pathogens they will encounter out in the world. Infections to premature babies can be deadly if not handled carefully.

Inability to maintain body heat - A premature baby is born with little body fat and immature skin which does not allow him or her to maintain body heat. Treatment involves warmers or incubators to help them keep warm.

NOTE: THERE ARE MANY OTHER COMPLICATIONS!