Miscarriages are common and often, unpreventable. Loss of pregnancy before 12 weeks is an early miscarriage and it happens in around 10% of all pregnancies. If you’ve experienced multiple miscarriages soon after conceiving without any logical explanation, it must be very frustrating. So, what causes early miscarriages at 6-8 weeks?
Normally, the early miscarriages are blamed on chromosomal abnormalities that result in the arrest of embryo growth and while that may be correct in some situations, it is not so for all. Miscarriages are caused by various factors at different times in the pregnancy and not knowing the reason can be frustrating.
To check the embryos for any aneuploidy (chromosomal imbalance), the doctors recommend preimplantation genetic testing for aneuploidy (PGT-A) before embryo implantation. While it has proven highly useful, this technique is not always accurate because the cells that are tested do not always represent the whole embryo.
The placenta and its precursor (the trophectoderm) tend to have more aneuploid cells and those are the ones tested with PGT-A. So, sometimes, despite being declared aneuploid by PGS testing, an embryo turns into a perfectly normal baby.
Chromosomal abnormalities of the embryo remain the most common cost of pregnancy losses in women but what else could be the reason of early miscarriages? Read below:
Less common reason for early miscarriages at 6-8 weeks:
Hyperactive immune system
An embryo comprises genetic material from both the father and the mother, which means that genetically it is always 50% foreign to the mother’s body and her immune system. In normal situations, during a pregnancy the immune system is reprogrammed to accept this embryo.
However, if your immune system is hyper-active or you have auto-immune diseases, the body may perceive the embryo as a foreign entity and the attack it. This results in embryo implantation problems, clinical pregnancies, and early miscarriages.
Maternal immunity problems are the most common cause of early miscarriages, after chromosomal abnormalities in the embryo.
Other causes of early miscarriages at 6 weeks to 8 weeks
Other than chromosomal and immunologic reasons, there are also other causes of early miscarriages including:
1. Anatomical abnormalities of the uterus
Uterine malformations can cause recurrent miscarriages if they remain undetected. A study published in the Journal Human Reproduction found that more than 65% of the women with septate uterus ended up having a miscarriage. Similarly, a bicornuate, unicornuate, didelphic, T-shaped, or tipped uterus can all cause early miscarriages. If you have large fibroids, your doctor may recommend removing them to allow for a safe pregnancy.
Not all fibroids need removal. A fibroid’s potential of causing miscarriage depends upon its location within your uterus.
Around 15% of all early miscarriages are caused by infections of some kind. Bacterial vaginosis (imbalance of vagina’s normal bacteria), HIV (human immunodeficiency virus), Gonorrhea, and cytomegalovirus (CMV) were all found to increase the risk of miscarriage.
3. Uncontrolled diabetes or high blood pressure
1,228 women with at least one previous miscarriage were examined. During the study, 797 women became pregnant and 188 or about 24 percent again suffered loss of pregnancy.
Even if they achieved normal blood pressure before the pregnancy, each 10 mm increase in systolic blood pressure was found to cause an 8 percent higher risk of miscarriage and each 10mm increase in diastolic blood pressure showed an 18 percent increased risk of miscarriage.
4. Thyroid disease
Hypothyroidism and raised TSH levels increase the chances of miscarriage in early pregnancy. TSH levels higher than 4.5 mU/L are associated with a greater risk of early miscarriage.
5. Blood clotting
Having genetic or hereditary thrombophilia raises your predisposition to blood clotting. Blood clots that develop in the placenta increase the risk of miscarriage and fetal loss. Some doctors advise all patients seeking IVF to test for “antiphospholipid syndrome,” so in case, it exists, it can be managed with medications for better chances of a successful pregnancy.
Medicines like Misoprostol, Methotrexate, retinoids, and some NSAIDS are harmful to pregnancy and may cause an early miscarriage. Never take any over-the-counter medication without your doctor’s advice during pregnancy.
7. Food poisoning
It will not always be the reason for miscarriage but some cases of food poisoning may be lethal for the growing embryo. Listeria, a bacteria that is sometimes found in soft, unpasteurized cheeses and other uncooked foods may cause miscarriage. Besides, undercooked eggs, raw meat may cause Salmonella, Toxoplasmosis, which can result in a miscarriage.
8. Environmental causes
Excessive exposure to harmful chemicals such as Lead, Arsenic, Mercury, pesticides, etc. may raise your risk of miscarriage. Be sure to discuss with your doctor to understand if your environment may be responsible for miscarriages.
While any of the above may be responsible for an early miscarriage at 6-8 weeks, the most common reasons for miscarriages are either chromosomal abnormalities in the embryo or immunologic problems in the mother.
If miscarriage is a concern, the doctors usually advise to do Karyotype testing in both parents to check the size, shape, and number of your chromosomes. If it comes out normal [normal female (45, XX) and normal male (46, XY)], the mother must be evaluated for immunological issues.
After a miscarriage happens, the doctor may also advise to test the products of conception (the fetus, placenta, and other pregnancy tissues) to check for chromosomal abnormalities.
If everything is normal, the maternal immune response and other causes must be evaluated before attempting a pregnancy again.
If you find the reason for your early miscarriage, it may be avoided. Consult with our top fertility specialists for early miscarriages and pregnancy problems.
Gleicher, N., Vidali, A., Braverman, J., Kushnir, V. A., Barad, D. H., Hudson, C., Wu, Y. G., Wang, Q., Zhang, L., Albertini, D. F., & International PGS Consortium Study Group (2016). Accuracy of preimplantation genetic screening (PGS) is compromised by degree of mosaicism of human embryos. Reproductive biology and endocrinology: RB&E, 14(1), 54. https://doi.org/10.1186/s12958-016-0193-6
Tullio Ghi, Francesca De Musso, Elisa Maroni, Aly Youssef, Luca Savelli, Antonio Farina, Paolo Casadio, Marco Filicori, Gianluigi Pilu, Nicola Rizzo, The pregnancy outcome in women with incidental diagnosis of septate uterus at first trimester scan, Human Reproduction, Volume 27, Issue 9, September 2012, Pages 2671–2675, https://doi.org/10.1093/humrep/des215
Sevi Giakoumelou, Nick Wheelhouse, Kate Cuschieri, Gary Entrican, Sarah E.M. Howie, Andrew W. Horne, The role of infection in miscarriage, Human Reproduction Update, Volume 22, Issue 1, January/February 2016, Pages 116–133, https://doi.org/10.1093/humupd/dmv041
Preconception Blood Pressure Levels and Reproductive Outcomes in a Prospective Cohort of Women Attempting Pregnancy https://doi.org/10.1161/HYPERTENSIONAHA.117.10705
Thyroid Status and Risk of Miscarriage: https://www.thyroid.org/patient-thyroid-information/ct-for-patients/volume-7-issue-12/vol-7-issue-12-p-3