Joined for Life

Patty Hensel's pregnancy in 1990 was uneventful. An ultrasound scan revealed an apparently normal fetus, although at one medical exam, Mike Hensel thought he heard two heartbeats, but he dismissed it as an error. Mike's ears weren't deceiving him though — he had heard two distinct heartbeats.

A cesarean section was necessary because the baby was positioned bottom-first. To everyone's amazement, the baby had two heads and two necks, yet it appeared to share the rest of the body, with two legs and two arms in the correct places, and a third arm between the heads. The ultrasound had probably imaged the twins from an angle that superimposed one head on the other. Patty, dopey from medication, recalls hearing the word "Siamese" and thinking she had given birth to cats. She had delivered conjoined, or Siamese, twins.

The baby was actually two individuals, named Abigail and Brittany. Each twin had her own neck, head, heart, stomach, and gallbladder. Remarkably, each also had her own nervous system. The twins shared a large liver, a single bloodstream, and all organs below the navel, including the reproductive tract. They had three lungs and three kidneys.

Abby and Britty were strong and healthy. Doctors suggested surgery to separate the twins. Aware that only one child would likely survive surgery, Mike and Patty chose to let their daughters be. In Ireland two years later, the parents of conjoined twins Eilish and Katie Holton faced the same agonizing choice, and they took the other option.

Eilish and Katie were similar to Abby and Britty but had four arms and a large, abnormal heart. In 1992, a team of fifteen doctors separated them. Katie died of heart failure four days after the surgery. Eilish, now a healthy child who gets around quite well on an artificial leg, still looks over her shoulder for her missing twin.

In 1993, U.S. physicians attempted to separate Amy and Angela Lakeberg, infants who shared a liver and heart. Doctors determined that Angela had the better chance to survive, so during surgery, they gave the heart to her. Amy died instantly. Angela lived until the following June, never able to breathe without the aid of a respirator.

Because Abby and Britty have separate hearts and nervous systems, they might fare better in surgery than the Holton or Lakeberg twins. But the girls are happy as they are, for now

(fig. 23C). They were particularly distressed to meet Eilish in 1995 to do a television program and learn the fate of Katie. Abby and Britty have very distinctive personalities and attend school, swim, ride bikes, and play, like any other kids.

Conjoined twins occur in 1 in 50,000 births, and about 40% are stillborn. Abby and Britty Hensel are rare among the rare, being joined in a manner seen only four times before. They are the result of incomplete twinning, which probably occurred during the first two weeks of gestation. Because the girls have duplicated tissue derived from ectoderm, mesoderm, and endoderm, the partial twinning event must have occurred before the three germ layers were established.

The term "Siamese twins" comes from Chang and Eng, who were born in Thailand, then called Siam, in 1811. They were joined by a ligament from the navel to the breastbone, which surgeons could easily correct today. Chang and Eng lived for sixty-three years, and each married. ■

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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