Pregnancy and abortion: How do they work?

Legal and medical descriptions of what’s happening inside the womb don’t always align
A lentil shows about how big a human embryo is when measured at six weeks of pregnancy.  At 15 weeks, the fetus is about the size of an apple, and at 20, about the size of a banana.  Pregnancy apps often use fruit to show the size of human development at different stages of pregnancy.    (PHOTO by Hyosub Shin /



A lentil shows about how big a human embryo is when measured at six weeks of pregnancy. At 15 weeks, the fetus is about the size of an apple, and at 20, about the size of a banana. Pregnancy apps often use fruit to show the size of human development at different stages of pregnancy. (PHOTO by Hyosub Shin /

Some words have become part of the lexicon of abortion. The original Roe v. Wade decision upheld abortion rights at least within the first “trimester.” A 1992 Supreme Court decision reaffirmed abortion rights until a fetus reached “viability.” Georgia’s soon-to-be law banning abortion at about six weeks is called the “Heartbeat Bill.”

According to medical experts, those words surrounding pregnancy and abortion may have personal or legal meaning, but their use is often not based on science.

Two generations of scientists have added to knowledge about pregnancy since the Roe ruling in 1973, when the Supreme Court justices established trimesters as a way to divide pregnancy into different stages to guide abortion decisions. Today, most women with a pregnancy app on their phone know more about the stages of development than the justices did then.

Still, as abortion battles heat up across the United States and in Georgia, misinformation can hold sway on both sides of the debate. Here are some basic facts about what’s happening inside a woman’s body once she conceives.

A “heartbeat”

For expecting mothers, an ultrasound visit to the doctor provides an opportunity to hear the sound of a heartbeat from the womb. It’s what Georgia’s law prohibiting abortion after six weeks was named for.

But, in the beginning, the sound isn’t an actual heartbeat.

“The sound that you’re hearing at six weeks is manufactured by the ultrasound machine,” said Dr. Nisha Verma, an OB-GYN who has studied at Emory and is currently a fellow at the American College of Obstetricians and Gynecologists in Washington, D.C.

At six weeks, what will soon be the heart hasn’t developed yet. What’s there is a tiny pipe called the primitive heart tube that can’t pump blood because it doesn’t close.

“For example, when I listen to (an adult’s heart, with a stethoscope), the sound that I hear is being made by the opening and closing of the cardiac valves. But at six weeks, those valves don’t exist,” Verma said. “It doesn’t have a sound.”

Instead, at about six weeks, cells are shooting out electrical signals and fluttering or twitching. The ultrasound machine translates that activity into something the doctor and patient can understand. The doctor needs to know if the signals are coming at a fast and regular rate.

In addition to the augmented sound, an ultrasound machine can take an image of an embryo too small to see well and magnify it to be watched on the screen. An embryo at six weeks is actually the size of a lentil or pea.

“You’ll see these images that make you think that a six-week pregnancy is like a full grown baby,” Verma said. “This is where there’s a lot of misconception out there.”


The definition of when a fetus becomes “viable,” or able to survive outside the womb, has changed with advances in neonatal care.

The Supreme Court’s 1992 Casey decision upholding Roe replaced the construct of trimesters with “viability” as the moment when the state had rights over a fetus. But the American College of Obstetricians and Gynecologists (ACOG) doesn’t use the term “viability” any more. The organization decided there was too much variability in when that moment occurs.

In 1973, when Roe v. Wade was decided, a baby born at 28 weeks had little chance of survival because the lungs are among the last organs to develop. But after scientists figured out how to keep the lungs developing outside the womb, they started saving even younger babies. Now at 25 weeks, if premature babies are given intense treatment, more than half survive and may thrive. Occasionally, a child born at 22 weeks can be saved.

A lot of early pregnancies — maybe even most of them — don’t make it.

Even before conception, things inside the womb can go awry. Eggs may have a genetic code that doesn’t work. The body works to ignore such eggs, but it sometimes selects them for fertilization.

After fertilized eggs implant in the uterus, the selection continues. From the first moments of pregnancy on, miscarriages can occur, which is often the body’s reaction to unhealthy DNA in the embryo.

No one really knows what the numbers are for failed pregnancies. “We do know, based on the studies, that probably somewhere between 40% to 60% of those embryos that implant, even transiently, failed to continue,” said Dr. Ruben Alvero, division director of reproductive endocrinology and infertility at Stanford Children’s Health in California.

“We’re very inefficient procreators as humans,” Alvero said. “Most of the genetic abnormalities that embryos have either never implant or, if they do implant, they most often result in a miscarriage.”

Most of the mothers never know.

“It is challenging to know how many pregnancies die post implantation because women don’t know that they miscarry this early in pregnancy,” said Dr. Julie Baker, a Stanford University researcher. “It is probably more common than we know.”

The ticking clock

Pregnant women: You’re further along than you think.

Common medical practice is to peg the beginning of pregnancy to the first day of the woman’s last period — that’s right, back when she wasn’t even pregnant yet. This practice on average adds about two weeks to the age of the pregnancy. So if a woman learns she’s pregnant when she’s two weeks late for her period, her pregnancy is officially six weeks old. That’s about the stage at which Georgia’s “Heartbeat Bill” abortion restriction would kick in, if it’s upheld in court.

Throughout pregnancy, fetal development and growth move extraordinarily fast.

That primitive heart tube that exists at six weeks within days and weeks becomes something else: puffing and looping itself around into the shape of a heart, with valves.

From six weeks to 17 weeks, the pea-sized embryo grows to a pear-sized fetus. In the beginning, the form starts as a circle, spends time in the shape of an amphibian, and even has ears on its neck at one point. Eventually, if the development proceeds smoothly, it all shifts and grows into the familiar form of a baby.

Feeling motherhood

Make no mistake: For many mothers and fathers, their baby’s life began the moment it was conceived.

No matter the stage of pregnancy, from the earliest moments, some women are deeply, physically invested as mothers, scientists have found. Others aren’t.

In a study published in the British medical journal The BMJ, Dr. Tom Bourne and other miscarriage researchers reported that a sizable number of abortions due to ectopic pregnancies resulted in post-traumatic stress disorder or PTSD.

“Some women and couples start relating to their embryo as a child as soon as they have received a positive pregnancy test,” the authors wrote in 2016. “For them, losing that embryo and perhaps observing the embryo or fetus being passed during the miscarriage may be equated with the catastrophic death of a child.”

Other researchers have also pointed to psychological damage to some women who were forced to carry dangerous or unwanted pregnancies.


An abortion at six or eight weeks is done differently than it was in 1973. Now, most women at that stage take a pair of pills. The “abortion pill” must be prescribed by a doctor.

The abortion pills are different from the “morning after” or Plan B emergency contraceptive pill, which does not require a prescription and works to prevent an egg from being fertilized or implanted. It must be taken within 24 to 72 hours after sex to be effective.

After taking the abortion pills, just as would happen with a miscarriage, the woman begins to bleed heavily as her uterus empties itself over a period of time. Like during a heavy period, the blood, much of it clotted, comes out in trips to the toilet, or on pads. The embryo comes out inside one of the blood clots, not something she can detect.

The abortion pills are approved for use up only until week 10 in the U.S. (or week 12 under the World Health Organization). In Georgia, more than 80% of abortions happen by week nine.

Until about week 16, doctors may perform abortion by suction, a process that is quick — “less than a few minutes,” Verma said. Among older fetuses, both miscarriages and induced abortions still happen. In Georgia, almost all abortions happen in the first half of pregnancy, by week 20, according to the Centers for Disease Control and Prevention. Less than 1% happen after 20 weeks.

All procedures have risks. But researchers say abortion is comparatively safe. The rates are too small to make solid comparisons between pills and surgical abortions, according to the CDC, but in general deaths have long averaged fewer than 1 death per 100,000 legal abortions. Depending on the data source, somewhere between 620,000 and about 900,000 abortions were reported in 2018 in the U.S.; two of those women died for reasons relating to the abortion.

The woman’s risk of death from giving birth is 14 times higher than her risk of death from abortion, according to Dr. Iffath Hoskins, a professor of obstetrics and gynecology at New York University.

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