Natural selection and the conception, pregnancy and birthing processes prevent abnormal babies. According to Dr. Ron Thompson, a miscarriage before 12 weeks of pregnancy is always due to a genetically imperfect conception, which is more common with increasing maternal age.
When a women goes in for her initial ultrasound around 10 weeks, hearing a fetal heartbeat equals a 95 percent chance of a perfect normal baby seven months later. “This is because the perfect genetics of natural selection have allowed the development of the organ systems,” says Dr. Thompson. “This can be diagnosed and reassured by the beating heart.”
In cases of in-vitro fertilization, the natural selection process is circumvented leading to an increased incidence of birth defects in IVF babies, states Dr. Thompson. When a woman gets pregnant naturally, 10 to 12 potential ova develop each month, but only one is allowed to become ovulated. The remaining ova are suppressed by local hormones in the ovaries.
During IVF, ovarian stimulating injected drugs, started on day two of the process, stimulate all potential ova in both ovaries. Stimulating all the ovum bypasses the natural selection process, allowing genetically imperfect ovum to develop to maturation. “It’s not unusual to have 10 to 12 ovum retrieved from IVF stimulation,” said Dr. Thompson. “Some of these ova will be genetically imperfect and still implanted in the woman.”
The IVF process, especially IntraCytoplasmic Sperm Injection (ICSI), also circumvents the natural selection of genetically abnormal sperm. In natural conception, intravaginal sperm capacitation accomplishes the natural selection of the spermatozoa. “This insures that only the perfect sperm can swim the 6 to 7 inches to the ovum, but also insures that the acrosome reaction is completed to allow actual fertilization,” states Dr. Thompson.
As Dr. Thompson explains, in normal laboratory sperm capacitation, scientists use a “swim up” technique to attempt to mirror the natural selection of the natural conception lubrication found in a woman’s reproductive tract. “In ICSI, the laboratory technician selects a single spermatozoa to inject into the ovum,” says Dr. Thompson. “This completely avoids natural sperm selection and can result in abnormal sperm fertilizing the ova.”