Pregnancy risks are not evenly distributed across a woman’s reproductive years. They follow a curve, with the lowest rates of most complications falling in the mid-20s to early 30s and rising on both ends of the age spectrum. Teenagers face elevated rates of preterm birth and preeclampsia, while women over 35 see a progressive increase in miscarriage, chromosomal abnormalities, gestational diabetes, and stillbirth. The climb in risk is gradual through the 30s, then steepens after 40. That pattern holds across dozens of large studies and national datasets, though the size of the increase varies by complication.
How Risks Shift by Age Group
The table below draws on several of the large studies and national datasets referenced throughout this article to show how common pregnancy complications change across maternal age groups. These are approximate rates pulled from different populations and study designs, so treat them as a guide to the overall pattern rather than exact predictions for any individual pregnancy.
| Complication | Under 20 | 20–29 | 30–34 | 35–39 | 40+ | 45+ |
|---|---|---|---|---|---|---|
| Miscarriage | ~10–13% | ~9–10% | ~11–15% | ~20–25% | ~40–51% | ~53–75% |
| Gestational diabetes | ~2.7% | Low–moderate | Moderate | Higher | ~14–16% | Higher still |
| Preterm birth (<37 wk) | Elevated | ~6–7% | ~5.7% | ~6–7% | ~7.8–10% | Higher |
| Stillbirth | Elevated | ~0.27% | ~0.31% | ~0.40% | ~0.53% | ~1.0–1.4% |
| Cesarean delivery | Lower | ~26% | ~26% | ~36% | ~43–50% | Higher |
A few patterns jump out. Miscarriage risk is the complication most dramatically affected by age, roughly doubling between the early 30s and early 40s, then climbing again steeply after 45. Preterm birth, by contrast, follows a gentler U-shape, with both very young and older mothers at somewhat higher risk but with much smaller absolute differences. Gestational diabetes and cesarean rates climb steadily from the late 20s onward without that U-shaped dip at the young end.
Miscarriage and Early Pregnancy Loss
Miscarriage is the risk that responds most sharply to maternal age. A large prospective register study in Norway found the risk was lowest in women aged 25 to 29, at about 10%, and rose rapidly after 30, reaching 53% in women aged 45 and over.1PubMed Central. Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study An earlier Danish register study covering over 600,000 pregnancies found even starker numbers at the upper end: a risk of about 9% in women aged 20 to 24, climbing to roughly 75% in those 45 and older.2PubMed Central. Maternal age and fetal loss: population based register linkage study The gap between those two estimates for women over 45 reflects differences in how the studies counted very early losses and the populations involved, but the direction is unmistakable: by the mid-40s, miscarriage is more likely than not.
The underlying reason is egg quality. As eggs age, errors during cell division become more common, producing embryos with the wrong number of chromosomes. Most of those embryos cannot survive beyond the first weeks, and the pregnancy ends before or shortly after a positive test. One review placed the age-related risk of miscarriage due to chromosomal problems at about 51% for women aged 40 to 44 and 93% after age 45.3Best Practice & Research Clinical Obstetrics & Gynaecology. Preconception tests at advanced maternal age
Chromosomal Abnormalities
The most widely known age-linked chromosomal condition is Down syndrome (trisomy 21), but it is not the only one. A Danish nationwide cohort of more than 500,000 pregnancies confirmed the well-established link between maternal age of 35 and above and higher risk of trisomy 21, trisomy 18, trisomy 13, and sex chromosome abnormalities.4PubMed Central. Maternal age and the risk of fetal aneuploidy: A nationwide cohort study of more than 500 000 singleton pregnancies in Denmark from 2008 to 2017 Interestingly, not all chromosomal errors tracked with age. That same study found no age-related association with triploidy or monosomy X, which are caused by different mechanisms.
Research into why advanced maternal age causes these errors has focused on how eggs divide. A report from the Atlanta and National Down Syndrome Projects found that the link between age and trisomy 21 was restricted to errors in the egg, not in the sperm or in errors after fertilization. Mothers of infants with Down syndrome due to one type of egg-division error were roughly 8.5 times more likely to be 40 or older than 20 to 24, and for a second type of error, the figure was about 15 times more likely.5PubMed Central. Maternal age and risk for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down Syndrome Projects The mechanism involves gradual degradation of the structures that hold chromosomes in place during cell division, compounded by oxidative stress and energy loss within the egg cell itself.6PubMed Central. Oocyte quality and aging
Gestational Diabetes
Gestational diabetes is one of the most consistent age-graded risks. U.S. vital statistics data show the pattern clearly: in 2021, mothers under 20 had a gestational diabetes rate of about 2.7%, while those aged 40 and above had a rate of about 15.6%, roughly six times as high.7Morbidity and Mortality Weekly Report. QuickStats: Percentage of Mothers with Gestational Diabetes, by Maternal Age — National Vital Statistics System, United States, 2016 and 2021 A meta-analysis pooling data from over 120 million participants across multiple countries found a steady dose-response: for each one-year increase in maternal age starting from 18, the risk of gestational diabetes rose by about 8% in the overall population. The increase was even steeper for Asian women, at roughly 13% per year.8Diabetes Research and Clinical Practice. Maternal age and the risk of gestational diabetes mellitus: A systematic review and meta-analysis of over 120 million participants
This matters because gestational diabetes is not just a blood sugar issue during pregnancy. It increases the odds of a large baby, shoulder injuries during delivery, cesarean section, and later development of type 2 diabetes in both mother and child. For women over 35 who are planning a pregnancy, getting a handle on insulin sensitivity beforehand through weight management and exercise can blunt some of this risk, though it cannot eliminate the age component entirely.
High Blood Pressure and Preeclampsia
Hypertensive disorders of pregnancy, which range from mild gestational high blood pressure to severe preeclampsia, become more common with age. A Japanese cohort study found that women aged 35 to 39 had nearly three times the odds of early-onset hypertensive disease compared to a younger reference group, and women 40 and older had about 3.5 times the odds. The effect persisted for late-onset forms of the condition as well, though it was somewhat smaller.9PubMed. Advanced maternal age is a risk factor for both early-onset and late-onset hypertensive disorders of pregnancy: the Japan environment and children’s study
When preeclampsia does develop in an older mother, the consequences tend to be worse. A study comparing preeclamptic women of advanced maternal age to younger preeclamptic women found the older group had about three times the odds of poor maternal outcomes overall, including higher rates of postpartum hemorrhage. Their babies also fared worse, with higher rates of prematurity, growth restriction, and low oxygen at birth.10PubMed Central. Maternal Perinatal Outcomes Related to Advanced Maternal Age in Preeclampsia Pregnant Women
Preterm Birth
The relationship between maternal age and preterm delivery follows a U-shaped curve rather than a straight line. A large French cohort study found the lowest preterm birth rates in women aged 30 to 34, at about 5.7%, with rates climbing for both younger and older mothers. Women under 24 and those over 40 had significantly higher preterm birth rates than that middle group, with the over-40 group reaching about 7.8%.11PubMed Central. Effect of maternal age on the risk of preterm birth: A large cohort study An Italian study confirmed the same U-shape, with the youngest and oldest mothers at the highest risk and women in their late 20s at the lowest risk for singleton births.12PubMed Central. The role of maternal age on the risk of preterm birth among singletons and multiples: a retrospective cohort study in Lombardy, Norther Italy
This U-shape is worth emphasizing because it means teen mothers share some of the same preterm-birth vulnerability as women over 40, just for different reasons. In younger mothers, socioeconomic factors and incomplete physical maturity are often involved. In older mothers, the elevated rates are more tightly connected to conditions like preeclampsia, gestational diabetes, and placental problems that themselves become more common with age.
Placenta Problems and Stillbirth
The placenta is the lifeline between mother and fetus, and age-related changes in uterine blood vessels increase the chance that it does not develop normally. Placenta previa, where the placenta covers or sits near the cervix, is two to four times more common in women over 30 to 34 compared to younger women.13PubMed Central. Risk Factors Associated With Placenta Previa: A Matched Case-Control Study 14American Journal of Obstetrics & Gynecology. The association of age and other risk factors with placenta previa Previous cesarean sections add to this risk, and since older mothers are more likely to have had prior cesareans, the effects can compound.
Stillbirth, defined as fetal death after 20 weeks, also rises with age. In a U.S. dataset, stillbirth rates per pregnancy were about 0.27% at ages 25 to 29, 0.40% at 35 to 39, and 0.53% at 40 and above.15Obstetrics & Gynecology. Advanced Maternal Age and Stillbirth Risk in Nulliparous and Parous Women According to ACOG, the national stillbirth rate reaches about 10 per 1,000 births for women aged 40 to 44 and nearly 14 per 1,000 for those over 45.16Obstetrics & Gynecology. Pregnancy at Age 35 Years or Older One finding that stands out: the age-related increase in stillbirth was strongest for first-time mothers and reduced or absent in women who had already delivered at least one baby, possibly because a first pregnancy conditions the uterine blood supply in ways that benefit later ones.15Obstetrics & Gynecology. Advanced Maternal Age and Stillbirth Risk in Nulliparous and Parous Women A separate analysis of U.S. birth records from 2003 to 2017 confirmed the increased stillbirth risk, finding about a 49% higher likelihood in women aged 40 to 49 compared to those aged 20 to 29, even after adjusting for other health conditions.17PubMed Central. Stillbirths among Advanced Maternal Age Women in the United States: 2003-2017
Risks at the Young End of the Spectrum
Most conversations about age and pregnancy focus on older mothers, but adolescent pregnancies carry their own set of elevated risks. A large Japanese multicenter study found that teen mothers had significantly higher rates of preterm birth, very preterm birth, low birth weight, and low Apgar scores compared to women aged 20 to 24.18PubMed Central. Preeclampsia and neonatal outcomes in adolescent and adult patients Preeclampsia is also more common among adolescents, and when it occurs alongside the other risks inherent to teen pregnancy, neonatal outcomes tend to be worse.18PubMed Central. Preeclampsia and neonatal outcomes in adolescent and adult patients
A Taiwanese nationwide birth cohort reinforced the picture: stillbirth, infant mortality, preterm birth, congenital anomalies, and neurodevelopmental problems were all highest in babies born to mothers under 20, dropped through the 20s, and then climbed again for mothers 30 and above in a reverse-J pattern.19PubMed. Revisiting maternal age and child health: A nationwide birth cohort study in Taiwan The reasons at the young end are a mixture of biological immaturity and social factors: limited prenatal care, poverty, and nutritional deficiencies all play a role, making it harder to tease apart how much is due to age alone.
What Happens After 40, and After 50
Pregnancy at 40 and beyond concentrates all of the age-related risks into a single package. A French study comparing women 40 and older to a reference group found significantly higher rates of preeclampsia (about 4.6% versus 1.5%), gestational diabetes (14.5% versus 6.9%), preterm birth (10.4% versus 6.5%), and fetal death in utero (2.1% versus 0.5%). Cesarean rates were dramatically higher too: about half of the women over 40 had emergency cesareans, compared to about 14% of the younger group.20PubMed Central. Pregnancy at 40 years Old and Above: Obstetrical, Fetal, and Neonatal Outcomes. Is Age an Independent Risk Factor for Those Complications? A Korean nationwide study confirmed the trend, showing that the odds of every measured complication, including gestational diabetes, hypertension, placenta previa, placental abruption, preterm delivery, and low birth weight, increased steadily with each year of maternal age.21PubMed Central. Nationwide Population-Based Cohort Study of Advanced Maternal Age and Obstetric Outcomes in Korean Women: Retrospective Cohort Study
Pushing even further, a study of women aged 50 and above found that this group had higher rates of gestational diabetes, cesarean delivery, and low Apgar scores compared to younger women. However, and this is where the data offers a surprising wrinkle, outcomes for women over 50 were not significantly worse than those of women aged 40 to 49.22PubMed. Perinatal Outcomes of Women Aged 50 Years and Above The risk curve seems to plateau somewhat in the 40s rather than continuing to climb indefinitely. One explanation is selection bias: women who become pregnant at 50 are often using donor eggs and receiving intensive medical supervision, both of which mitigate the risks that would otherwise be expected.
Egg Age Versus Body Age
One of the most telling findings in reproductive medicine is what happens when you separate the age of the egg from the age of the mother. In IVF, older women can use eggs from younger donors, which lets researchers compare pregnancies where the body carrying the baby is older but the egg is young. A propensity-matched analysis of women with advanced maternal age found that those using donor eggs and those using their own eggs (after genetic screening of embryos) had similar implantation rates, miscarriage rates, gestational ages at delivery, and birth weights.23PubMed. In vitro fertilization and perinatal outcomes of patients with advanced maternal age after single frozen euploid embryo transfer: a propensity score-matched analysis of autologous and donor cycles The key qualifier is that the autologous (own-egg) group had their embryos screened for chromosomal normalcy before transfer, meaning only genetically normal embryos were used in both groups.
This matters because it isolates egg quality as the dominant driver of age-related pregnancy loss and chromosomal problems. When the egg is healthy, the older body can carry a pregnancy about as well as a younger one for many outcomes. That said, the gestational complications driven by the mother’s cardiovascular and metabolic health, things like preeclampsia and gestational diabetes, are related to the body’s age and are not fixed by using younger eggs. Declining egg quality remains the core problem, and no effective treatment exists to reverse it once it has occurred.24PubMed. BDNF secreted by mesenchymal stem cells improves aged oocyte quality and development potential by activating the ERK1/2 pathway
Paternal Age Is Part of the Picture
Maternal age gets the vast majority of the attention, but the father’s age also matters. Sperm quality declines with age, bringing increases in DNA mutations and chromosomal errors.25PubMed Central. Impact of Advanced Paternal Age on Fertility and Risks of Genetic Disorders in Offspring About 80% of all brand-new genetic mutations in a child come from the father’s side, and the number of these mutations rises with the father’s age at conception.26Fertility and Sterility. The impact of paternal age on new mutations and disease in the next generation These new mutations are linked to conditions that develop later in a child’s life, including autism, schizophrenia, and certain childhood cancers.25PubMed Central. Impact of Advanced Paternal Age on Fertility and Risks of Genetic Disorders in Offspring
The practical takeaway is that couples in which both partners are older face a double contribution of risk: egg-quality-driven chromosomal errors from the mother and new-mutation-driven genetic changes from the father. This does not mean older couples cannot have healthy pregnancies, but it does mean that focusing exclusively on the mother’s age gives an incomplete picture.
What Screening and Monitoring Look Like for Older Parents
Advanced maternal age alone is not considered reason enough for invasive diagnostic procedures like amniocentesis. Current guidance encourages women 35 and older to undergo cell-free DNA screening, a blood test that analyzes fragments of fetal DNA circulating in the mother’s bloodstream, along with a detailed ultrasound. If those screening tests raise a concern, amniocentesis remains available and is considered relatively safe.27PubMed Central. Management of Pregnancy in Women of Advanced Maternal Age: Improving Outcomes for Mother and Baby
For women using IVF, preimplantation genetic testing can screen embryos for chromosomal problems before transfer. A three-arm study comparing standard IVF, non-invasive chromosome screening, and traditional preimplantation genetic testing found that both screening approaches roughly quadrupled the odds of a live birth compared to standard IVF in women of advanced maternal age, while cutting pregnancy loss rates substantially.28PubMed Central. Efficacy of non-invasive chromosome screening, preimplantation genetic testing for aneuploidy, and morphological grading in selecting embryos of patients with advanced maternal age: a three-armed prospective cohort study
Newer research is also exploring combined mid-pregnancy testing that measures both placental hormone levels and blood flow to the uterus. In women of advanced maternal age, this dual approach improved the ability to predict preeclampsia and growth restriction beyond what any single test could do on its own.29PubMed. Assessing placental endocrine and vascular function for prenatal prediction of adverse pregnancy outcomes in advanced‑maternal‑age pregnancies This kind of targeted surveillance for older mothers reflects a broader shift: rather than treating age as a single all-or-nothing threshold, clinicians are moving toward layered risk assessments that take multiple factors into account simultaneously.
Postpartum Recovery and the Pelvic Floor
Age does not only affect pregnancy and delivery. It also influences how the body recovers afterward. A study examining the pelvic floor muscles of women after their first vaginal delivery found that maternal age visibly affected recovery at the molecular level. Older mothers showed changes in how their levator ani muscle, the main muscle supporting the pelvic floor, remodeled and repaired itself after birth. The biological processes involved in this recovery overlapped with those affected by age more broadly, suggesting that older mothers may be more susceptible to long-term pelvic floor issues like organ prolapse.30PubMed Central. Transcriptomic evidence of remodeling in postpartum levator ani muscle associated with maternal age and recovery time after first vaginal delivery
This is an area that gets very little attention in the standard discussion of pregnancy risks by age, which tends to focus on what can go wrong during pregnancy or delivery. But for many women, the complications that affect daily quality of life years later, including urinary incontinence and pelvic organ prolapse, are among the most consequential outcomes of childbearing. The finding that age compounds the recovery challenge adds another dimension to the risk picture that goes beyond the nine months of pregnancy itself.