Human reproduction Conception to Birth

How does a female get Pregnant? Can be planned or unplanned – possibility happens ANY time an ovum and a sperm come in contact with each other Implanted – fertility doctor Sexual Intercourse Can happen even if a couple uses the “withdrawal” method Can happen even if a couple uses birth control

Why so many Sperm? Long way to travel (15-18 cm or 6-7 inches) Not every sperm makes it all the way through Many defected sperm 50-50 chance of making it into the correct fallopian tube Could take 30 minutes or up to 2 days for sperm to make it to the egg Sperm that find the egg, release an enzyme from their acrosome (tip of the sperm) that breaks down the sheath around the egg Only one sperm is allowed into the egg cell The fertilized egg changes its chemical composition that blocks other sperm from entering

Period of the Zygote Begins when egg is fertilized in the fallopian tube. Period of rapid cell division Forms a blastocyst Ends 2 weeks later when the zygote is implanted in the wall of the uterus

Period of the Zygote continued

Period of the Embryo From 3 to 8 weeks after conception Body parts are formed during this period Embryo rests in the amnion filled with amniotic fluid Umbilical cord joins embryo to placenta

Period of the Fetus From 9 weeks after conception to birth Increase in size and systems begin to function Age of viability: 22 to 28 weeks

First Month By the end of the first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

First Month

Two Months The embryo is about 1 inch long and has distinct, slightly webbed fingers. Veins are clearly visible. The heart has divided into right and left chambers.

Around two months

Three Months By now the fetus is 2 1/2 to 3 inches long and is fully formed. He has begun swallowing and kicking. All organs and muscles have formed and are beginning to function.

Four months Your baby is covered with a layer of thick, downy hair called lanugo. His heartbeat can be heard clearly. This is when you may feel your baby's first kick.

Lanugo

About four months

Five Months A protective coating called vernix caseosa (white/gray covering visible on new borns) begins to form on baby's skin. Your baby will be nearly 8 inches long and weigh almost a pound.

Six months Eyebrows and eyelids are visible. Your baby's lungs are filled with amniotic fluid, and he has started breathing motions. He can hear what is going on around him.

Getting closer to full term

Seven Months Your baby weighs about 3 1/2 pounds and is about 12 inches long. His body is well-formed. Fingernails cover his fingertips

Seven Months

Eight Months Your baby is gaining about half a pound per week, and layers of fat are piling on. He has probably turned head-down in preparation for birth. He weighs between 4 and 6 pounds.

Eight Months

Nine Months Your baby is a hefty 6 to 9 pounds and measures between 19 and 22 inches. As he becomes more crowded, you may feel him move less.

Nine Months and recap

Placenta

Birth At 1:30