What is Early Pregnancy Loss?
Early pregnancy loss can be grouped into two different categories based on when the loss happens. Sometimes the embryo just won’t implant, which is still a loss for the patient, though not technically considered a miscarriage. These types of losses are considered implantation failures and can manifest with either a negative pregnancy test or a biochemical pregnancy (which is a very early loss typically around 4-5 weeks when there is a positive blood test but nothing visualized on ultrasound). Most clinically recognized miscarriages occur later, most commonly between 5-9 weeks.
When an embryo doesn’t implant or begins implantation but stops developing soon after (biochemical pregnancy), the most common cause is a chromosomal abnormality in the embryo itself (meaning it has too much or too little genetic material). Advancing age of the female partner increases the chance that the embryo will be abnormal.
Repeated Implantation Failure
When implantation failure occurs over and over again, further investigation and treatment is warranted. Preimplantation genetic testing of the embryos that can be performed with in vitro fertilization should be considered in order to confirm that an embryo is chromosomally normal before it is transferred back into the uterus. Further evaluation of the uterus with a surgery called hysteroscopy may be warranted. There are new tests that can be used in the setting of frozen embryo transfers that allow us to personalize the endometrial preparation to enhance endometrial receptivity and improve implantation.
First Trimester Miscarriage
Miscarriages occur in 10-20% of all pregnancies. However, the loss rate may actually be higher as losses before 6 weeks may not be recognized as the woman just thinks her period is delayed and doesn’t realize she is pregnant. Most first trimester miscarriages occur before 8-9 weeks, but are sometimes not recognized until a few weeks later.
Risk Factors for Miscarriage
The likelihood that you will miscarry is greatly influenced by your age. The older you are the more likely you will miscarry, with miscarriage rates increasing from about 15% at age 20, to 30% by age 40 and over 50% by age 45. There are other risks of miscarriage including previous miscarriage, extremes of weight, the use of toxic substances like cigarettes and moderate to high alcohol consumption. There is some data that suggests untreated celiac disease may increase the chance of miscarriage. Uncontrolled endocrine issues, such as thyroid and diabetes can increase the miscarriage rate.
Causes of Miscarriages
The vast majority of miscarriages in the first trimester are caused by chromosomal abnormalities, most commonly meaning that the embryo has the incorrect amount of genetic material inside (too many or too few chromosomes), however there can be other types of abnormalities in the chromosomes. Significant birth defects are thought to be the second most common cause. If the structure of the uterus is abnormal that can also cause a miscarriage.
Testing with Miscarriages
Even with the first miscarriage, it is our preference to obtain genetic testing on the pregnancy if at all possible to help determine the cause of the loss. New technology exists that can better detect if a genetic abnormality was the reason for the loss.
Moving Forward after a Miscarriage
After one pregnancy loss it is important to do a thorough clinical review of the woman’s medical history to discover any risk factors for miscarriage that need to be addressed. However, once those clinical issues are addressed, there is no need for further treatment after one loss and women should try to conceive on their own again. There is no need to delay getting pregnant after a miscarriage.