Archie Bunker's Place: In the Season 3 episode "Sex and the Single Parent," where Stephanie's friend who is in junior high reveals to her in secret that she is pregnant. Unknown to them, Archie silently listens in ... and it is this that will shape his future views about sex education being taught in school.
In the original series, Brandon briefly dated a scholarly senior girl, only to learn that she was a teen mother. Later occurred a couple of seasons later, when Kelly found a baby and discovered that his mother was a teenage girl (played by a young Jessica Alba, pre-Dark Angel).
In the new series, Adrianna gets pregnant, can't have an abortion when she goes because it's too late, wants to keep it but eventually puts it up for adoption. Harry also didn't know that his high school sweetheart had a kid and put it up for adoption until he moved back to LA.
In The Borgias, Lucrezia is married at 14 and has her first child, Giovanni, at around 15. While early motherhood was common back then, this particular situation was fairly unusual even then and dangerous for the health of both mother and child. Incidentally, the child's father isn't her (much older) husband, but a commoner with whom she fell in love.
A comedian on BET's Comicview joked about having a young mother: "My mama was fourteen when she had me. You know what that was like growing up? When I was a kid I'd be struggling with my homework, she'd be at the other end of the table struggling with her homework, neither one of us can play outside till we're finished..."
Cobra Kai: Carmen Diaz gave birth to Miguel when she was just 18 years old.
Sarah Louise Platt got pregnant at the age of thirteen and carried her daughter Bethany to term. A few years later when Sarah was out of school but still a teenager, she got pregnant a second time. She gave birth prematurely and the baby died after a few days.
Cranked up a notch years later when Faye was given a pregnancy storyline. She was twelve at the time.
Degrassi High: Erica and Tessa both got pregnant. Both got abortions. The only difference is that Tessa's baby daddy is Joey Jeremiah. In some instances, Erica's pregnancy created a minor What Happened to the Mouse?, as the second part of the episode was not broadcast.
Manny gets pregnant in season 3 when she was in 9th grade, and ends up having an abortion. Unsurprisingly, this two-part episode didn't air in the US on the first run, especially since her decision was portrayed as the right thing to do, and she never regretted it.
Liberty gets pregnant in season 5 when she's in 11th grade, carries the baby to term, and gives him up for adoption.
Mia enters the show in season 6 when she is in 10th grade and already has a two-year-old daughter, Isabella. Mia is nicknamed 'Mamma Mia'. The show follows her as she juggles motherhood, school, and a blossoming modeling career.
Emma has a pregnancy scare in season 6 when she is in 12th grade, but in the end she isn't really pregnant.
Anya fakes her pregnancy in season 10 to get back at her ex-boyfriend Sav and make him drop out of the school presidential run. After Sav finds out the truth, they actually get back together and continue to lie about the pregnancy, then later tell everyone that Anya had had a miscarriage.
Jenna (who provides the page quote) gets pregnant in season 10 when she's in 10th grade. She tries to be a mother to her son Tyson, but gives him up for adoption after a few weeks.
Alli has a pregnancy scare in season 12 when she's in 11th grade. She realizes she missed a few birth control pills and was really scared that her period would be late.
18 year old Dallas is introduced in season 12, and it's revealed he has a three-year-old son that lives with the child's mother.
The Dinosaurs episode "Network Genius" had a scene featuring a parody of Beverly Hills, 90210 called Pangaea Hills: Dino210. The scene had a teenage dinosaur tell her friend that she was "in trouble". When he asks her to prove it, she responds by showing that she has laid an egg.
Quinn, which ends up as a major problem for her as not only is she president of the school's celibacy club but has never had sex with her boyfriend. The father is actually his best friend, Puck.
Also Played for Laughs in the second season. Brittany tells Santana that she thinks she has a bun in the oven, which becomes the talk of the school. Later, it turns out she's not actually pregnant, she just thought she was, because she saw a stork outside her bedroom window (even though storks live nowhere near Ohio). This is Brittany we're talking about. It's possible she mistook some other bird for a stork.
Izzie had a daughter at sixteen and gave her up for adoption.
One episode had the police find a newborn baby in the dumpster behind a middle school. The doctors treat the baby and spend the rest of the episode trying to figure out who the mother is. Four suspects were taken to the hospital, while their parents all denied their own child was the mother.
Many characters in Hollyoaks got pregnant as teenagers: Cindy Cunningham, Theresa McQueen, Sinead O'Connor, Leela Lomax, Sienna Blake, Frankie Osborne. Amy Barnes had two children while still in her teens, and Myra McQueen had three; but the "winner" has to be Amber Sharpe, who got pregnant at twelve, before she was even a teenager.
Hot in Cleveland had an episode revealing that Joy had given a child up for adoption when she was a teenager.
House: In Season 5, Cuddy adopts the baby of a teenager who died of eclampsia a few weeks after giving birth.
Jane on Jane the Virgin is the result of this, leading to her mother Xiomara being barely in her forties when Jane is 23 at the start of the series.
Just Shoot Me!: It turns out that Nina had a daughter when she was fifteen, and meets her many years later. Then she learns her daughter did the same thing, and she's also a grandmother. Nina faints at the news.
The protagonist of Life Unexpected is a 16 year old girl that was never successfully adopted that seeks emancipation. She was conceived during a one-night-stand her parents had at their winter formal in high school.
Pops up frequently in Law & Order: Special Victims Unit. In a couple of episodes, a young teenager's pregnancy is what raises the alarm about her being abused; in others, an already-known victim finds that she is pregnant and has to figure out how to handle it.
One episode centered around a pregnant teen who had run away to New York to get an abortion because she was afraid her father would kick her out if he found out about the baby. When she wasn't able to obtain the abortion (due to the fact that she ended up in a sham/decoy clinic instead of a real one), she had her boyfriend beat her on the abdomen to try and induce a miscarriage.
Season 7's "Come, Let Us Reason Together," where 17-year-old Nellie Oleson gives birth to twins. Her husband, Percy, is at least 10 years older than Nellie.
Also in Season 7, "Sylvia," where the titular character is implied to be 14 when she is impregnated by a rapist.
Season 8's "Days of Sunshine, Days of Sorrow," where Laura is barely 18 when she gives birth to Rose. Almonzo, by contrast, is 28.
An episode of Masters of Horror directed by John Carpenter has a teenage girl get raped by an alien and has to go have it aborted. Her father (Ron Perlman) and brothers attempt to stop it and in the end, the baby alien ends up saving her life by killing her father.
Laurie Windrow from Midnight Caller is the daughter of Jack Killian's high school prom date.
One of the overarching plots of Mom's first season is Violet's unexpected pregnancy and how she has to come to grips with the impact it has on her goals. She's also the third (at minimum) teen mom in their Dysfunctional Family, after her mother Christy and grandmother Bonnie. In one episode Christy had an Imagine Spot where she pictured her future granddaughter continuing the cycle.
In My Wife and Kids, Jay got pregnant with her and her husband Michael's first-born Junior when she was 16. A few seasons later, Junior gets his girlfriend Vanessa pregnant when they're both 18.
A past plot on Neighbours was about a teenage girl who got pregnant and wanted to put it up for adoption, but the child's father wanted custody. They eventually get back together and decide to keep the baby.
In Night and Day, Jane Harper fell pregnant with Sam Armstrongs child aged fifteen, but had an abortion.
One Life to Live's Jessica Buchanan finds herself in this situation. After the requisite waffling over abortion and adoption, she decides to keep the baby, only to lose it after being hit by a car.
One Tree Hill: More or less the whole premise of the show, as both Scott brothers are the result of this - Lucas from a high school relationship, and Nathan from one only a few months later as their father started college. Nathan himself ends up having a child with fellow high-schooler Haley during their senior year.
Party of Five Season 2 features a Very Special Episode where Julia gets pregnant and spends the whole episode debating what to do with the baby. She decides that she will have an abortion, but suffers a miscarriage before she can.
Private Practice, as if it didn't already have enough drama, has quite a few of these the biggest one being Sam and Naomi's daughter Maya's teen pregnancy, which includes getting married to the father of the baby.
Exaggerated in Raising Hope: Virginia and Burt are grandparents in their late 30s/early 40s, having had their son Jimmy in their mid-teens (15 and 17, respectively). Jimmy himself is just outside this trope having had Hope in his early 20s. Virginia's mother had her at about twenty, leaving her to be Raised by Grandparents. Jimmy's great-great grandmother was revealed to be alive in one episode, dying at 104 years of age while her own daughter was in her eighties, so she also counts.
Reba opens with this issue in the characters' mind, due to Cheyenne being pregnant while she's a teenage high school student, though it's not the only issue facing the family.
The Republic of Sarah: It's mentioned that Corinne had her son Josh as a teenager. She thinks his father is Danny, though only Danny and Corinne are aware of this at first. Corinne gets a DNA test and Sarah tells her that Adam, her husband, actually fathered him, though this turns out to be a lie; Danny is the father.
Resident Alien: Asta has this as part of her backstory. She had a baby at 16 with her abusive boyfriend and was pressured into giving it up for adoption. That baby is later revealed to be Jay.
Roseanne Darlene gets pregnant and gives birth to a premature daughter, Harris Conner Healy.
Carla's friend from Scrubs. Elliot accidentally offended her by assuming that her son was a boyfriend, when in actuality she had him at age 14.
Used several times (unsurprisingly) on 7th Heaven. Most notably averted, however, when the Camdens' daughter Mary turns up preggers, but she denies having had sex when confronted by her parents. It was a clerical error at the doctor's. The real pregnant person was Mary's mom Annie, pregnant with the Camden twins.
Tanya, the lead character's 18-year-old daughter who has a three-year-old son in Single Father. The circumstances surrounding the child's conception (who the father is, etc.) are left unstated, but it is heavily implied that estrangement from her father as a teenager contributed to the pregnancy.
A running gag on The Steve Harvey Show as never-seen character Tameka is in Cedric's third-period health class, has two children, and is always available to assist with child-rearing questions.
On Strong Medicine, as Dr. Lu Delgado tries to caution teenage girls against having sex and stresses the importance of using birth control should they decide to, she reveals, "I'm 30 and my son is 14", thus enabling the girls to do the math and realize that her son is the result of this.
Later in the series, her son himself finds himself in this situation. Until he realizes that the timing of the pregnancy means he can't be the father.
Supergirl (2015): In her backstory, Samantha Arias became pregnant as a teen and was kicked out of the house for it. In the present, she is raising her daughter Ruby as a single mother. Then Samantha finds out she is really a genetically engineered Kryptonian, but having the baby delayed her Puberty Superpower and they are slowly emerging now. She is then brainwashed into becoming the cold and ruthless Reign, who has full control of her powers.
Zandra, Salene and eventually Amber also get pregnant on this show (although Salene miscarries and Zandra dies before her baby is born ), which is weird because these four are the four original older female mall rats.
The premise of TLC's reality show, High School Moms.
Justin Suarez from Ugly Betty is the result of this. Hilda had him in her senior year of high school after getting pregnant at the prom.
Both Katherine and Isobel from The Vampire Diaries gave birth to daughters as teenagers who were given up for adoption (although, as noted in the article above, teenage pregnancy as a concept did not really exist when Katherine gave birth to her daughter in 1490). In her case the scandal is because she's not married.