Risks and Reasons for Premature Birth

woman on floorAny baby born before 37 weeks in the womb is considered premature. In the United States, 12 to 13% of babies were born prematurely in 2008. This number is increasing. Babies born early have higher risks of damage to their central nervous system as well as respiratory, gastrointestinal, and other complications. The more premature the birth, the more potential problems exist.

There are three general groups of preterm birth.

  1. The spontaneous beginning of early labor.
  2. The preterm, premature rupture of membranes (bag of waters), or PPRM, which eventually leads to early labor or other means of delivery.
  3. Delivery early, by labor induction or C-section, because of problems with the baby or the mother. This is called an indicated preterm delivery; it is necessary for the health of the mom or baby.

Indicated preterm delivery means there is a critical reason to deliver the baby early. They are increasing in the USA. Indicated preterm delivery is often necessary:

  • For artificially-conceived, multiple pregnancies. Even single babies may have to be delivered early after artificial conception.
  • Because of preeclampsia or eclampsia. Preeclampsia is a disease of pregnancy in which the mother-to-be experiences very high blood pressure, severe stomach ache, protein in the urine, swelling and headache. If the baby is not delivered, the mother can have full-blown eclampsia with risk of seizures, and even death. The environment for the baby inside the womb is also not safe.
  • Because of intrauterine growth restriction which causes 30 to 35% of premature births. This means that there is not enough room in the womb for the baby to continue to grow. This may cause premature labor, or it may be recognized that the baby is not growing and needs to be delivered safely.

65 to 75% of preterm births are due to preterm labor and PPRM. These have multiple causes, some of which are:

  • Infection of the womb and or membranes;
  • Vascular diseases which can reduce the amount of blood and nutrients getting to the baby;
  • An overly full uterus holding too many babies, or really big babies;
  • Problems with the placenta.

There are many known risk factors for preterm births. Risk factors include:

  • A recent previous birth, less than six months from previous delivery.
  • A previous preterm birth. The risk of a repeat preterm birth ranges from 15 to 50%. This may be because the mother has an underlying medical problem.
  • A history of preterm births in other family members. There is definitely a genetic component to premature birth.
  • In the US, being black, African-American or Afro-Caribbean. Women in these groups have 2 to 3 times the preterm birth rate of white women; the births are often very early.
  • Nutritional status. Low body mass index is a factor which increases risk, as do low levels of iron, folate and zinc.
  • Obesity. Obese women have higher risk of pre-eclampsia, diabetes, very large babies, and babies with congenital anomalies. All of these can cause preterm birth. However, by itself, obesity seems to protect against preterm birth.
  • Multiple fetuses. 60% of twins are born preterm. This can be because of early labor or PPRM. It can also be indicated because of problems with the mother or babies. With more than twins, almost all babies are delivered preterm due to uterine overdistension.
  • Bleeding. Any bleeding during pregnancy is associated with a higher risk of preterm birth.
  • Mother's medical problems like asthma, diabetes, or high blood pressure. These can pose a risk to the mother, as well as make conditions in the womb bad for the baby.
  • Surgery or infections. An appendectomy can stimulate contractions, leading to preterm birth. So can certain kidney or other serious infections.
  • Physically strenuous or stressful work.
  • Smoking, drug and alcohol use by the mother. Chemicals in cigarette smoke, including nicotine and carbon monoxide reduce the blood flow to the placenta.
  • Intrauterine infection. This is a frequent and important cause of preterm birth. If the infection gets into the amniotic fluid, it can get to the fetus. This can lead to preterm labor and fetal injury.
  • Genital infections. This can include syphilis, gonorrhea, and trichomoniasis and bacterial vaginosis.
  • Periodontal disease. It is unclear how this presents a risk.

What can be done to reduce the risk?

  1. Try to leave more time in between pregnancies.
  2. Gain the right amount of weight with your pregnancy. It is not the time to diet even if you are overweight. Your obstetrician will give you guidelines.
  3. Make sure any chronic illnesses are under control before you get pregnant, if possible. You may need to be seeing an internist or family practitioner in addition to your obstetrician to take care of high blood pressure or diabetes. Make sure the doctor you are seeing is comfortable treating pregnant women – you can ask. Diabetic control is especially important.
  4. Take your prenatal vitamins.
  5. Make sure your teeth and gums are healthy.
  6. Do not smoke at all, drink alcohol, or use recreational drugs.
  7. If you have a history of any genital infection, tell your doctor. Report any symptoms immediately.
  8. Also be aware of other infections. If you have pain when urinating, that could indicate a bladder infection. Get treated before it spreads to your kidneys.
  9. Make sure your doctor knows if premature births run in your family.

There are things your doctor may be able to do to assess your risk, and possibly lower it by treating infections, and sometimes with medication like progesterone during part of your pregnancy.


Between 40 and 70% of women who have premature contractions actually go into labor. The rest do not.

There are ways to try and stop or delay preterm labor. There are also interventions to improve the outcome for the baby.

If you have risk factors for preterm delivery, be sure and discuss this with your obstetrician.

What do you think?

Risks and Reasons for Premature Birth

Tell us what you think!


  1. Kenzi says:

    My son was born at 35.6 weeks and I didnt have any issues during pregnancy. Thank God he didnt have any issues, was at the right weight gestationaly and all. No one knows why he came early, but i like to say he just couldnt wait to see us 🙂

  2. katherine says:

    My baby was to big n i had a small tummy!


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