Overall miscarriage risk is 17-22%; risk after gestational sac is visible is 12-15%
Miscarriage is one of the most frequent problems in human pregnancy. The most widely accepted definition is that proposed by the World Health Organization in 1977. The incidence among clinical pregnancies (a pregnancy that is confirmed by both high levels of hCG and ultrasound confirmation of a gestational sac) is about 12-15%, but including early pregnancy losses it is 17-22%.
After heartbeat is detected, risk of miscarriage is 9.4% at 6wks; 4.2% at 7wks; 1.5% at 8wks; 0.5% at 9wks
To estimate the risk of miscarriage among asymptomatic women after a prenatal visit between 6 and 11 weeks of gestation where proof of fetal viability of a singleton was obtained by office ultrasonography at the same visit. METHODS: Those recruited were 697 asymptomatic women who attended their first antenatal visit between 6 (+2 days) and 11(+6 days) weeks of gestation, where evidence of fetal cardiac activity of a singleton was obtained by office ultrasonography. RESULTS: The risk of miscarriage among the entire cohort was 11 of 696 (1.6%). The risk fell rapidly with advancing gestation; 9.4% at 6 (completed) weeks of gestation, 4.2% at 7 weeks, 1.5% at 8 weeks, 0.5% at 9 weeks and 0.7% at 10 weeks.
Second trimester miscarriage risk is 0.5%; higher with previous delivery or miscarriage
OBJECTIVE: To estimate the risk of second-trimester miscarriage in women with low risk of carrying a fetus with chromosomal abnormality. The study population comprised 14,278 singleton pregnancies with a low risk of Down syndrome. RESULTS: The miscarriage rate was 0.5%. After having controlled for maternal age, we found the number of previous deliveries and miscarriages to independently predict miscarriage: odds ratio for each previous delivery 1.48; odds ratio for each previous miscarriage 1.34. Excluding women with any previous miscarriage and adjusting for parity, we found a U-shaped relationship between maternal age and miscarriage. CONCLUSION: In singleton pregnancies with low risk of Down syndrome at 12-14 weeks, the spontaneous fetal loss rate before 25 weeks is likely to be around 0.5%. NT thickness up to 3 mm does not seem to affect the risk of miscarriage in such pregnancies. Instead, the risk seems to increase with number of previous miscarriages and deliveries, and possibly the risk is highest in the youngest and oldest women.
Age and Miscarriage
Miscarriage risk increases 12% after age 30; goes up 39% after age 35; doubles after age 40
In a large cohort of patients who received infertility treatment, the odds ratios regarding risk of miscarriage were as follows: age <30 odds ratio = 1; age 30-34.9 odds ratio = 1.12; age 35 to 39.9 odds ratio = 1.39; age >40 odds ratio = 2.62.
Miscarriage risk increases after age 35; increases 5 fold after age 40
There was no difference in odds of miscarriage below the age of 35 years, but the odds rose sharply thereafter, with a 75% increase for mothers aged 35–39 years and a five-fold increase where the mother was aged 40 and above (relative to mothers aged 25–29 years).
Miscarriage risk doubles after age 40 and triples after age 45
With adjustment for gravidity and number of previous miscarriages, the relative risk of miscarriage remained near unity through age 30 years, after which it increased to 2.0 at age 40 years and 3.0 at age 45 years.
Having a partner over 40 years old increases risk of miscarriage by 60%
The adjusted odds ratio for spontaneous abortion was 0.59 for pregnancies conceived from fathers aged younger than 25 years compared with those from fathers aged 25-29 years. For fathers age 40 years or older the odds ratio for spontaneous abortion was 1.6 when compared with the same reference group. Logistic regression was used to adjust for maternal age, maternal diabetes, maternal smoking, history of miscarriage before the index pregnancy, parity at interview, and interval between the index pregnancy and the interview.
Risk of miscarriage increases by 43% when partner is age 35, by 90% at age 50
The risk of miscarriage between weeks 6 and 20 of pregnancy was studied using a model adjusted for maternal age. Among women aged less than 30 years, the hazard ratio of miscarriage associated with paternal age of 35 years or more was 1.56 for first trimester miscarriage. When male age was coded into smaller categories, the adjusted risk of miscarriage was lowest when the man was aged less than 25 years and highest when the man was aged more than 45 years. The hazard ratios predicted for paternal ages of 35, 40, 45, and 50 years were, respectively, 1.43, 1.58, 1.74, and 1.90. In conclusion, the risk of miscarriage increased with increasing paternal age.
Miscarriage risk increases 88% if the father is over 50 years old
The paternal age-related risk of late fetal death was higher than the risk of early fetal death and started to increase from the age of 45 years. Pregnancies fathered by a man aged 50 or more years had almost twice the risk of ending in a miscarriage compared with pregnancies with younger fathers (odds ratio = 1.88), after adjustment for maternal age, reproductive history, and maternal lifestyle during pregnancy.
Miscarriage risk doubles for those who need more than a year to successfully conceive
Among those who had consciously tried to conceive, there was a strong trend of increasing odds of miscarriage with
increasing length of time to conception, reaching a doubling in odds for those who took more than a year to conceive relative to those conceiving within 3 months.
Previous Losses and Miscarriage
After two miscarriages, one still has a 91.2% chance of successful pregnancy; drops to 20% after 7
Subsequent Live Birth Rate According to the Previous Number of Miscarriages
Previous number of miscarriages 2 3 4 5 6 7
- Live birth rate for the first
pregnancy after examination 76.3% 66.1% 59.0% 53.3% 31.3% 13.3%
- Cumulative success rate 91.2% 82.9% 76.0% 73.3% 56.3% 20.0%
-Abnormal embryonic karyotype 68.3% 56.5% 65.0% 25.0% 28.65% 20.0%
Miscarriage risk increases with previous losses, smoking, and working outside the home
The risk of early miscarriage was higher for women with a past history of early miscarriage; odds ratio was 1.98 for one previous miscarriage, 2.36 for two, and 8.73 for three or more. Other factors also influence risk; an odds ratio of 2.39 was found for women who smoked, and 1.65 for women working outside the home.
Risk of miscarriage only increases by 7% after one loss; nearly doubles after three or more
In a large cohort of patients who received infertility treatment, the odds ratios regarding risk of miscarriage and previous pregnancy loss were as follows: no previous miscarriages: odds ratio = 1, one previous miscarriage: odds ratio = 1.07, two previous miscarriages: odds ratio = 1.39, three or more previous miscarriages: odds ratio = 1.92.
Miscarriage risk is normally 2% after a heartbeat is seen; but 18% in women with recurrent miscarriage
In women with repeat miscarriage, an embryonic heart rate predicted a successful live birth in 82%, compared with 98% in control women. (Found via transvaginal sonography between 6 to 8 weeks of gestation). The mean embryonic heart rate from successful pregnancies in the control group (143.2 beats per minute) was significantly higher than the mean in women with a history of repeat miscarriage (131.4 beats per minute).
Infection and Miscarriage
Vaginal infections found in 31.5% of first trimester miscarriages, 3.6% of controls
In this study, we analyzed the tissues relative to the product of conception from abortions and miscarriages during the first trimester (51 miscarriages and 56 voluntary pregnancy interruptions) in women. Specimens were investigated by cultural methods for the presence of yeasts, gram positive, gram negative bacteria, and genital mycoplasma. None of these agents could be found in voluntary pregnancy interruption samples, with the exception of 3.6% of specimens positive for adenovirus, whereas miscarriage tissues were positive for at least one microrganism by 31.5%.
Vaginal infections increase the risk of midterm miscarriage and preterm labor
Overall, 1425 of the 3217 cultures (44.3%) were positive. The micro-organisms most frequently found were: yeasts (44%), Ureaplasma urealiticum (29%); group B streptococcus (15%); and bacterial vaginosis (11%). Cervicovaginal cultures were found positive in 84.6% of preterm premature rupture of membranes, 55.0% of term premature rupture of membranes, 50.8% of preterm deliveries, 43.8% of mid-trimester miscarriages, 31.4% of intrauterine deaths and in 33.5% of controls. Among the 11,212 cervicovaginal cultures considered in the second study, an overall 56.2% were positive, 43% in asymptomatic women.
Urinary tract infections increase miscarriage risk
In a survey of 100 interstitial cystitis patients, the incidence of first time and habitual miscarriage was extremely high.
Other Traits and Miscarriage
Morning sickness associated with 70% reduction in miscarriage risk
Women who suffered from nausea and sickness in the first 12 weeks of pregnancy were almost 70% less likely to miscarry, with a marked increasing trend of reducing odds with increasing severity of nausea.
Conceiving on the day of, or just before ovulation, halves miscarriage risk
Conceptions on days - 1 or 0 with respect to the natural family planning estimated day of ovulation were considered to be "optimally timed," and all other conceptions were considered as "non-optimally timed." The miscarriage rate was similar for optimally timed conceptions (9.1%) and non-optimally timed conceptions (10.9%). However, among women who had experienced a miscarriage in a prior pregnancy, the rate of miscarriage in the index pregnancy was significantly higher with non-optimally timed conceptions (22.6%) as compared with optimally timed conceptions (7.3%). This association was not observed among women with no history of miscarriage . The adjusted relative risk of miscarriage among women with non-optimally timed conceptions and a history of pregnancy loss was 2.35. The excess risk of miscarriage was observed with both preovulatory and postovulatory conceptions.
16.7% of threatened miscarriages actually end in miscarriage
A sample of women with threatened miscarriage and healthy pregnant women (control group) was studied. RESULTS: 16.7% pregnancies in the study group ended missed miscarriage vs. none in the control group . 20% threatened miscarriers delivered between 24(th) and 37(th) weeks of gestation, whereas 10% preterm deliveries occurred in the controls.
Induced abortion increases the risk of miscarriage 128% for up to 2 years
When comparing women who had had a previous pregnancy with primigravidae (first pregnancy), women whose 1 previous pregnancy ended in induced abortion, those whose 2 previous pregnancies ended in induced abortion, and those who had at least 1 induced abortion in their 3 or more previous pregnancies faced an increased risk of miscarriage (odds ratio = 1.41, 4.43, and 1.35, respectively). The researchers found the same risk when they adjusted for vaginal infection. Second trimester abortions were associated with an increased risk of first miscarriage (odds ratio = 4.63). Women whose last induced abortion occurred 12-24 months before the current pregnancy with no pregnancy in between the induced abortion and the current pregnancy faced an increased risk of miscarriage (odds ratio = 2.28). There was no increased risk of miscarriage when the induced abortion occurred at least 24 months before with no pregnancy in between the induced abortion and current pregnancy, suggesting that the uterus requires time to recover before successful future implantation.
For a concise list of qualities found to affect one's risk of miscarriage, see:
Random Miscarriage Data
Recurrent miscarriage increases risk of stillbirth 1300%, preterm birth 60%, ectopic pregnancy 160%
The obstetrical histories of 455 women who had experienced two or more consecutive miscarriages were studied for the occurrence of term births, preterm births, stillbirths, miscarriages, ectopic pregnancies, and hydatidiform moles. The ratio of observed to expected values was term births 0.1, preterm births 1.6, stillbirths 14.0, miscarriage 6.6, ectopic pregnancy 2.6, and molar pregnancy 7.1. The gravid specific proportions of reproductive outcomes were constant suggesting comorbidity or common cause(s). The commonality that links these types of reproductive failure will provide insight into the mechanisms of reproductive wastage.
High blood pressure and high hematocrit associated with restricted growth in the first trimester
Factors such as maternal high blood pressure and high hematocrit levels (the proportion of blood that consists of red blood cells) are associated with a greater likelihood of restricted fetal growth during the first trimester, with restricted growth linked to an increased risk of preterm birth and low birth weight, according to a study in the February 10 issue of JAMA.
Bacteria in the mouth associated with preterm birth
Bacteria in the mouths of pregnant women can contribute to preterm birth, according to researchers from Case Western Reserve University, Cleveland, Ohio, and Hathaway Brown School, Shaker Heights.
Each miscarriage raises risk of future heart attack by 40%
In women 50-74 years of age who had experienced pregnancy, history of miscarriage tended to be associated with a higher risk of myocardial infarction (age-adjusted odds ratio: 2.1), and the risk increased significantly with the number of miscarriages (age-adjusted odds ratio per miscarriage: 1.4). These results suggest that women who experience repeated miscarriages may be at an increased risk of cardiovascular disease later in life.