Pregnancy Loss Causes and Risk Factors Print Can Breastfeeding During Pregnancy Cause Miscarriages? Written by Written by Krissi Danielsson Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage. Learn about our editorial policy Krissi Danielsson Updated on June 24, 2019 Getty Images/(c) Jaime Monfort More in Pregnancy Loss Causes and Risk Factors Symptoms and Diagnosis Your Options Physical Recovery Coping & Moving Forward Everyone's heard the advice that "breast is best" for feeding new babies, but what happens when you get pregnant with a new baby while you're still nursing your older one? Is nursing during pregnancy safe? Breastfeeding and Miscarriage Although there are numerous conflicting opinions on the issue of breastfeeding during pregnancy, no research has ever found an increased risk of miscarriage in women who continue breastfeeding an older child during pregnancy. In the past, doctors used to advise women to stop nursing when they became pregnant again. The concerns were that breastfeeding could deprive the developing baby of nutrients or stimulate uterine contractions (because breastfeeding causes increased oxytocin levels, which also can cause uterine contractions). But there is no conclusive evidence that this occurs and babies born to mothers who breastfed during pregnancy appear to be perfectly healthy. The consensus is that it's up to the moms to decide whether to keep nursing during a new pregnancy. In a few high-risk conditions, such as placenta previa, doctors may advise increased caution but for most, nursing during pregnancy is probably safe. What Does Cause Miscarriage? About 3 of 4 miscarriages occur during the first trimester of pregnancy. These miscarriages are usually attributable to a problem with the fetus. Miscarriages that happen during the second trimester are often attributable to a health problem that the mother is experiencing. In women aged 30 years or fewer, about 1 of 10 pregnancies end in miscarriage. This estimate doubles among women aged 35 to 39 to 2 of 10 pregnancies resulting in miscarriage. First-Trimester Miscarriage About 2 of 3 first-trimester miscarriages are due to chromosomal abnormalities in the fetus. Chromosomes contain all our genetic information in the form of genes. A fetus with an abnormal number of chromosomes can either have too many or too few chromosomes. Often, when there are chromosomal abnormalities, the fetus doesn't have the needed information to develop properly and miscarriage results. Just because a mother experiences miscarriage due to chromosomal abnormalities of the fetus once does not necessarily mean that the problem will happen again. Furthermore, a miscarriage attributable to chromosomal abnormalities doesn't mean that either the mother's or father's chromosomes are faulty. Aside from chromosomal abnormalities, miscarriage during the first trimester can also occur because of the following: Placental problems (the placenta nourishes the fetus)SmokingDrug useObesityAlcohol use Second-Trimester Miscarriage As mentioned above, miscarriage during the second trimester is often attributable to underlying health conditions that the mother is experiencing including the following: High blood pressureDiabetesKidney diseaseAutoimmune diseaseThyroid disease Certain infections experienced by the mother may also increase the risk of miscarriage. These infections include the following: SyphilisChlamydiaRubellaGonorrheaHIVRubellaFood poisoning (listeriosis, toxoplasmosis, and salmonella) In addition to chronic health conditions and infection, second-trimester miscarriage can also be attributed to the following: Weakened cervixFibroidsIrregularly shaped uterusPCOS What Doesn't Cause Miscarriage? As we've already mentioned, breastfeeding during pregnancy is an unlikely reason for the miscarriage. Here are some other factors that don't cause miscarriage: Sex during pregnancyLifting during pregnancyExerciseStress or depressionSudden shock or fright Was this page helpful? Thanks for your feedback! Get diet and wellness tips delivered to your inbox. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. La Leche League, "Breastfeeding During Pregnancy." 8 Sept 2006. Moscone, S.R., M.J. Moore, "Breastfeeding during pregnancy." Journal of Human Lactation Jun 1993. Continue Reading