How many babies can fit inside one woman?

Answers to your questions about the news.
Jan. 27 2009 3:31 PM

Womb for More

How many babies can fit inside one woman?

Bunch of babies. Click image to expand.
How many babies can fit in a woman?

A woman gave birth to octuplets in California Monday after 30 weeks of pregnancy. The six boys and two girls ranged in weight from 1 pound, 8 ounces, to 3 pounds, 4 ounces. How many babies can fit inside a pregnant woman?

There's no scientific limit, but the largest reported number of fetuses in one womb was 15. In 1971, Dr. Gennaro Montanino of Rome claimed to have removed 15 fetuses from the womb of a 35-year-old woman. The largest number of babies ever delivered was in Australia in 1971, when a 29-year-old women gave birth to nonuplets. They all died. (Decaplets were supposedly born in Brazil in 1946, but that report is unconfirmed.) The largest set of children to be born together and survive—not including this week's octuplets, who are all still alive—is seven. A set of septuplets born in Iowa in 1997 became the first to survive infancy. At least two more sets of septuplets have since been born and survived.

How do so many babies fit in one woman? The limit isn't so much the number of babies as their volume and weight. In general, once the total weight of the babies inside reaches about 12 pounds, the uterus goes into labor. The greater the number of fetuses, the earlier the labor will occur. (The rough formula for due dates is to start at 40 weeks of gestation for one baby and subtract three weeks for each additional child:  37 for twins, 34 for triplets, etc. It's remarkable, then, that eight fetuses were able to gestate for 30 weeks, as in the California case.) Labor can also occur if a sac ruptures and introduces bacteria into the uterus or if one of the fetuses isn't growing correctly and signals the uterus to induce labor. (Scientists still don't know exactly what causes labor to start.) But for safety reasons, multiple births are often carried out before labor naturally occurs, and almost always by cesarean section. If the uterus gets too big and the fetuses too heavy, it can be difficult for the woman to breathe. The amount of placental tissue can also cause the mother to develop pre-eclampsia, or pregnancy-related hypertension.

Don't the babies get tangled up?   Usually not. * Normally, each baby is enclosed in its own amniotic sac, which keeps the various umbilical cords and limbs from getting intertwined. Picture a bucketful of water balloons. In each sac, there's plenty of fluid—about two-thirds the volume of the fetus—for the baby to move around in. After the sacs break, the babies can get tangled up during birth—so-called interlocking twins—which is why doctors usually opt for cesarean section. It is possible to have monoamniotic twins, or fetuses that share the same sac, with dangerous results: Cords can get compressed or entangled and cut off the babys' oxygen and food supply.

Got a question about today's news? Ask the Explainer.

Explainer thanks Joshua A. Copel of Yale University Medical School and Thomas Moore of University of California, San Diego.

Correction, Jan. 30, 2009: This article originally stated that fetuses in multiple births always have their own amniotic sacs. ( Return to the corrected sentence.)

TODAY IN SLATE

History

The Self-Made Man

The story of America’s most pliable, pernicious, irrepressible myth.

Does Your Child Have Sluggish Cognitive Tempo? Or Is That Just a Disorder Made Up to Scare You?

Mitt Romney May Be Weighing a 2016 Run. That Would Be a Big Mistake.

Amazing Photos From Hong Kong’s Umbrella Revolution

Rehtaeh Parsons Was the Most Famous Victim in Canada. Now, Journalists Can’t Even Say Her Name.

Television

See Me

Transparent is the fall’s only great new show.

Doublex

Lena Dunham, the Book

More shtick than honesty in Not That Kind of Girl.

What a Juicy New Book About Diane Sawyer and Katie Couric Fails to Tell Us About the TV News Business

Rehtaeh Parsons Was the Most Famous Victim in Canada. Now, Journalists Can’t Even Say Her Name.

  News & Politics
Damned Spot
Sept. 30 2014 9:00 AM Now Stare. Don’t Stop. The perfect political wife’s loving gaze in campaign ads.
  Business
Moneybox
Sept. 30 2014 11:25 AM Naomi Klein Is Wrong Multinational corporations are doing more than governments to halt climate change.
  Life
Atlas Obscura
Sept. 30 2014 10:10 AM A Lovable Murderer and Heroic Villain: The Story of Australia's Most Iconic Outlaw
  Double X
Doublex
Sept. 29 2014 11:43 PM Lena Dunham, the Book More shtick than honesty in Not That Kind of Girl.
  Slate Plus
Behind the Scenes
Sept. 30 2014 10:59 AM “For People, Food Is Heaven” Boer Deng on the story behind her piece “How to Order Chinese Food.”
  Arts
Brow Beat
Sept. 30 2014 10:48 AM One of Last Year’s Best Animated Shorts Is Finally Online for Free
  Technology
Future Tense
Sept. 30 2014 7:36 AM Almost Humane What sci-fi can teach us about our treatment of prisoners of war.
  Health & Science
Bad Astronomy
Sept. 30 2014 7:30 AM What Lurks Beneath the Methane Lakes of Titan?
  Sports
Sports Nut
Sept. 28 2014 8:30 PM NFL Players Die Young. Or Maybe They Live Long Lives. Why it’s so hard to pin down the effects of football on players’ lives.