Miscarriage is a huge, almost taboo subject, that few women talk about as its incredibly distressing, and it’s usually only when they go through it that they discover how many of their friends and family have been there too. A really large proportion of miscarriages go unrecognised as most happen before the start of a period is even expected, and it’s believed that up to 50% of all pregnancies don’t progress, but most of these are lost very early, with 10-15% of pregnancies being lost later on.i
There are two sides to miscarriage; the bad side is the awful loss, the upside is that it proves the couple can conceive (and the truth is not all pregnancies “were meant to be”), but things get really difficult for the 5% of couples who have 2 consecutive miscarriages, and even worse for the 1% who have 3 or more losses in a row, in a condition called “recurrent miscarriage”. Of the recognised miscarriages:ii
- 80% are in the first 12 weeks
- 90% are in the first 16 weeks
The usual signs of miscarriage are bleeding, often with cramping and pain in the lower abdomen, and if this happens seek medical advice at the local “early pregnancy unit”. However light bleeding is quite common in the first 12 weeks of pregnancy, so it doesn’t necessarily mean a miscarriage is happening. When a baby’s lost after 20 weeks (or its over 500g) it’s usually termed a “stillbirth”, but sometimes medics use the term “spontaneous abortion” which can confusing and upsetting for the rest of us.
There are 5 different types of miscarriage:
- Threatened miscarriage where there are mild symptoms of bleeding, usually with little or no pain, and the cervix is closed. A scan will show irregular shaped “hypo-echogenic” areas behind the gestational sac, and the risk of miscarriage is between 4-33% depending on the stage of pregnancy
- Inevitable miscarriage involves heavy bleeding with clots and pain, the cervix is open, the bleeding may be severe enough for the woman to collapse and unfortunately the loss of the baby is inevitable
- Missed miscarriage is a situation where the fetus has died and still held in the womb, but pregnancy tests will remain positive for several days. The symptoms of pregnancy may have decreased or gone and there can be a persistent dirty, brown discharge, and ultrasound scans show there’s no fetal heart beat
- Incomplete miscarriage is when there has been heavy bleeding and the miscarriage has been confirmed, but “retained products of conception” (either the amniotic sac or placenta) remain in the womb
- Recurrent miscarriage is the consecutive loss of three or more pregnancies for a couple
A miscarriage is deeply upsetting, but its reassuring to know that most couples (76%) will be pregnant with a healthy baby within the year.iii If it’s not the first miscarriage consider preserving some of the tissue lost (contact lens solution works) so it can be tested for chromosomal problems that have little bearing on future pregnancies. If the chromosomes are OK it indicates other investigations are needed, though some couples may wish to have preimplantation genetic diagnosis (PGD) if they’re having IVF.
The risk of miscarriage varies with age, lifestyle, health history and immune state, and the ten main causes of miscarriage are:
- Chromosomal abnormalies
- Placental problems
- Immune issues
- Antibiotic use
- Abnormalities of the uterus or cervix
- Hormonal abnormalities
- Lifestyle choices (cigarettes, alcohol, coffee, drugs)
- Bacterial infections
- Polycystic ovary syndrome (PCOS)
- Extra or missing chromosomes in a fetus create a condition called ‘aneuploidy’. Humans have 23 pairs of chromosomes and a matching pair of 46 are needed for healthy offspring (with 23 coming from each parent) but a fetus with more or less than 46 chromosomes has significant problems that usually leads to an inevitable miscarriage. However its possible for baby’s to be born with some variations, such as Downs Syndrome (three of chromosome 21), and one-off mistakes in the sperm or egg are usually the cause.
- DNA fragmentation is when some of the genetic material on the chromosomes get’s broken off; it something that happens to some DNA in all eggs and sperm, but the higher the level of damage the more difficult it is for chromosomes in an embryo to repair and fill the damaged material. In this situation implantation is usually fine, but as cells divide and replicate the problems with
iThe management of early pregnancy loss, Royal College of Obstretricians and Gynaecologists (2006) 2. Wilcox AJ, Weinberg CR, O’Connor JF, et al; Incidence of early loss of pregnancy. N Engl J Med. 1988 Jul 28;319(4):189-94.
iiTang OS, Ho PC. The use of misoprostol for early pregnancy failure. Curr Opin Obstet Gynecol. 2006;18:581-586
iiiHassan MAM, Killick SR: Is previous aberrant reproductive outcome predictive of subsequently reduced fecundity? Hum. Reprod.20(3),657–664 (2005).
ivJoining the Immunological Dots in Recurrent Miscarriage Bansal, A. S. (2010), American Journal of Reproductive Immunology
vPropst AM, Hill JA (2000). “Anatomic factors associated with recurrent pregnancy loss”. Semin. Reprod. Med.18 (4): 341–50. doi:10.1055/s-2000-13723. PMID11355792.
vi“Use of antibiotics during pregnancy and risk of spontaneous abortion” Flory T. Muanda, MD, Odile Sheehy, MSc, Anick Bérard, PhD. CMAJ May 1, 2017 vol. 189 no. 17 E625-E633
viiMaternal Subclinical Hypothyroidism and Thyroid Autoimmunity in Early Gestation Are Associated with Increased Risk of Miscarriage. Pearce Elizabeth N. Clinical Thyroidology. September 2014, 26(9): 235-237. doi:10.1089/ct.2014;26.235-237.
viiiLevothyroxine-Treated Women in Their Reproductive Years Should Have their Serum TSH Adjusted Before Conception to Prevent Hypothyroidism in the First Trimester. Mestman Jorge H. Clinical Thyroidology. October 2014, 26(10): 254-257. doi:10.1089/ct.2014;26.254-257.
ixJovanovič, L., Liang, Y., Weng, W., Hamilton, M., Chen, L., and Wintfeld, N. (2015) “Trends in the incidence of diabetes, its clinical sequelae, and associated costs in pregnancy“. Diabetes Metab Res Rev, 31: 707–716. doi: 10.1002/dmrr.2656.
x Bacterial vaginosis and infertility: cause or association?” Magdy AM. J Obstet Gynecol Reprod Biol. 2013
xi “Co-morbidity of cervical incompetence with polycystic ovarian syndrome (PCOS) negatively impacts prognosis: A retrospective analysis of 178 patients” Yongqing Wang Et al. BMC Pregnancy and Childbirth201616:308. DOI: 10.1186/s12884-016-1094-6