Usually, when a woman becomes pregnant, her body initiates several biological processes aimed at preventing simultaneous pregnancy, including the release of hormones to stop ovulation. But in rare cases, a pregnant woman can continue ovulating, or release an egg, and this egg can then be fertilized with sperm and implanted in the uterus, I mentioned Live Science earlier. This rare phenomenon, in which two fertilized eggs are implanted in the uterus at different times, is known as “overload”.
In this new case, the twins were born with a difference of three weeks According to Good Morning America. The mother, Rebecca Roberts, was 39 and became pregnant for the first time last year after trying to conceive for several years and taking fertility drugs.
At 12 weeks of pregnancy, doctors discovered a second baby on an ultrasound that had a three-week difference in size from the first. Due to the rarity of overloading, Roberts’ doctors were initially unable to explain the size difference between the two babies.
“My initial reaction was how I missed the second twin,” Dr. David Walker, an obstetrician and gynecologist at Royal United Hospital in Bath, told Good Morning America. And then [I] I felt a little relieved because it wasn’t my fault it was an extraordinary pregnancy. ”
Doctors diagnosed Roberts with breastfeeding, and told her that a toddler might not survive. When Roberts was 33 weeks pregnant, last September, doctors induced labor because the younger twin, Rosalie, had stopped growing properly due to a problem with the umbilical cord.
The older twin, Noah, stayed in the neonatal intensive care unit (NICU) for three weeks, and Rosalie was stayed for 95 days. Both babies are now at home and in good health.
“When we put them next to each other, it feels like they immediately know – and they communicate and touch each other’s faces, which is the most beautiful thing,” Roberts told Good Morning America. “The twins have an amazing bond anyway, but the story between these two is, when they get old enough to discover it, they’ll feel a lot more special.”
It is not clear how many overloads occur; Many cases may go undetected because the fetuses are so close in age and thus size that they are thought to be a normal twin, according to a Live Science report. Most of the known cases of pregnancy include patients who have used assisted reproductive techniques such as in vitro fertilization. According to Healthline.
However, this phenomenon is thought to be extremely rare, because three separate, improbable events have to occur: ovulation (which is normally stopped by pregnancy hormones), and fertilization (which is usually stopped early in pregnancy when a “mucus plug” forms to prevent sperm from passing. Via the cervix) and implantation (which requires enough space for another fetus in the womb, plus hormones that would normally not be released once a person is already pregnant), according to Healthline. But in other animals – such as fish, hares, and badgers – overload is actually common.
Originally published on Live Science.