Pregnancy and Fetal Development
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00:00Hey, too fast!
00:11Oh!
00:12Oh!
00:13Ah!
00:14Well, I guess that was bound to happen.
00:18Dear Tim and Moby, How does a baby grow?
00:22From Eric.
00:24The human development process starts when an egg cell is fertilized by a sperm cell.
00:30Some babies are born with a male reproductive system, which can produce sperm cells.
00:36Others are born with a female reproductive system, complete with about 100,000 egg cells
00:40or ova.
00:41They are contained in the ovaries, two small organs on either side of the uterus.
00:47At puberty, ovaries begin to release one egg into the fallopian tubes each month.
00:53While the egg is moving through the tubes, it can be fertilized by a sperm cell.
00:58During sexual intercourse, sperm cells are released from the penis, a male reproductive
01:03organ.
01:04Out of the hundreds of millions of sperm cells released, it takes only one to fertilize the
01:09egg.
01:10The egg cell and sperm cell join together to make a whole new cell called a zygote,
01:15a fertilized egg cell.
01:18The zygote divides into two cells, then four cells, then eight, and so on.
01:24It splits about once every 20 hours until it's a hollow ball called a blastocyst.
01:30The blastocyst travels through the fallopian tubes and into the uterus.
01:35It attaches to the lining of the uterus about a week after fertilization.
01:39Yep, the pregnancy has begun.
01:43Over about nine months, that clump of cells will grow into a baby.
01:49Pregnancy is usually divided up into three trimesters, each about three months long.
01:54Things happen really fast in the first trimester.
01:58After about two weeks, the blastocyst becomes an embryo.
02:02Cells begin to specialize to form body systems, starting with the nervous system.
02:07The embryo gets nutrients from the placenta, tissue that connects it to the mother.
02:12The placenta passes oxygen, water, and nutrients to the embryo through a tube called the umbilical
02:17cord.
02:19Waste from the embryo flows through the cord to the placenta.
02:22Then it passes into the mother's circulation to be eliminated.
02:26Your belly button is where your umbilical cord used to be attached.
02:30Well, not you.
02:34During the first trimester, the embryo starts to develop limbs, a heart, and muscles.
02:40Its eyes and ears move into place on its head, and a doctor can even hear its heartbeat.
02:45Yeah, pregnant people experience all kinds of physical and emotional changes.
02:52Their abdomen gets bigger and bigger to make room for the growing baby.
02:56Blood flow to the kidneys increases, which means more trips to the bathroom.
03:01And hormones, chemical messages sent throughout the body, cause their mammary glands in their
03:06breasts to expand.
03:08These glands will eventually produce and store milk to feed the baby, if the mom chooses
03:13to breastfeed.
03:15Changes to hormone levels have all kinds of other effects, too.
03:19They can cause unusual food cravings, since they affect our senses of taste and smell.
03:24They also influence appetite, which increases to provide enough nourishment for the baby.
03:29But sometimes it may seem like the opposite, since changing hormone levels can also cause
03:34nausea.
03:35All of these changes to a pregnant person's body and lifestyle can affect their mood and
03:41leave them feeling exhausted.
03:44By the end of the first trimester, the embryo has grown into a three-inch fetus.
03:49During the second trimester, the fetus continues to develop organs and body systems.
03:55And the brain grows a lot.
03:58Fetuses begin to sleep and wake at about week 18.
04:03Around then, doctors can use a scan, called an ultrasound, to show if it's male or female.
04:09By 26 weeks, its brainwaves look like those of a full-term baby, one that's ready to be
04:13born.
04:15Pregnant people usually feel a bit better and more energetic during the second trimester.
04:20And they can start to feel the fetus moving around.
04:24By the end of the second trimester, the fetus is a little more than a foot long and weighs
04:28two to three pounds.
04:30It's pretty much finished developing body structures by now, but it still has a lot
04:33of growing to do.
04:35In fact, it gets so big in the third trimester that it has to pull its knees up to its chest
04:40to make room in the womb.
04:42Gravity starts to pull the big head down.
04:45The baby turns upside down and moves into the lower abdomen, ready to be born.
04:51Most of us are born head first.
04:53Oh yeah, it's normal for someone who's pregnant to feel anxious or scared about the birth.
05:00It can be quite painful, and there's always the chance of complications.
05:04With today's medical practices, though, childbirth is usually safe and straightforward.
05:09It's also super common for expecting parents to feel anxious, nervous, or even sad about
05:14the coming baby, along with feeling happy and excited.
05:19Becoming a parent is a major change in a person's life.
05:22Learning how to juggle the responsibilities of a baby, relationships, work, and everything
05:26else can feel really stressful.
05:29Many new parents experience bouts of sadness or worry that will eventually fade.
05:35For the one who gave birth, hormonal changes can add to the struggle.
05:39In any parent, the changes that come with a new baby can cause postpartum depression
05:43or postpartum anxiety.
05:46It can be tough, but the right support and treatment can help them feel better.
05:51And mostly, parents come to enjoy the experience of having children.
05:55It's a lot of hard work, but after all, it's how families are made.
06:00Well, I don't think robots have babies the same way that humans...
06:12Um, I have no response to this.