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Preterm Birth

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Preterm Birth (Premature Birth)

Delivery before 37 completed weeks of gestation. Preterm babies face higher risks of respiratory, neurological, and developmental complications. Associated with insufficient gestational weight gain.

Definition

Preterm birth (also called premature birth) is defined as delivery occurring before 37 completed weeks of gestation, counting from the first day of the last menstrual period. A full-term pregnancy spans 37–42 weeks; delivery between 37 and 41+6 weeks is term; at or after 42 weeks is post-term.

Preterm birth is the leading cause of neonatal mortality globally and a significant cause of long-term disability. India has one of the highest absolute numbers of preterm births in the world due to population size and the prevalence of risk factors including undernutrition, anaemia, and infections.

Key Things to Know

  • IUGR and preterm birth often co-occur but are distinct — a baby can be preterm with appropriate weight, or term but growth-restricted.
  • Adequate gestational weight gain per IOM guidelines is one modifiable risk factor.
  • The Pregnancy Due Date Calculator helps accurately track gestational weeks.

Related Calculators

Pregnancy BMI Calculator →Calculate your pre-pregnancy BMI and get IOM-recommended gestational weight gain range. Track your current pregnancy weight gain and stay on target for a healthy pregnancy.
Pregnancy Due Date Calculator →Calculate your pregnancy due date from your last menstrual period (LMP). Know your gestational age, trimester, and days remaining using Naegele's rule.

Related Terms

Gestational Weight GainGestational Weight Gain (GWG)IOM GuidelinesInstitute of Medicine Gestational Weight Gain Guidelines (2009)IUGRIntrauterine Growth RestrictionPre-eclampsiaPre-eclampsia

Frequently Asked Questions

Yes. Women who gain less than the IOM-recommended minimum for their BMI category have a higher risk of spontaneous preterm birth, likely because insufficient maternal nutrition affects placental function and cervical integrity. Conversely, excessive weight gain is associated with indicated preterm birth (medically initiated early delivery) due to complications like pre-eclampsia and gestational diabetes. Tracking gain with the [Pregnancy BMI Calculator](/pregnancy-bmi-calculator/) helps identify under-gaining early.
Survival rates for preterm babies in India depend heavily on gestational age and NICU access. Babies born at 34–36 weeks (late preterm) have very high survival rates (95%+) with brief NICU support. Those born at 28–33 weeks have 70–90% survival in well-equipped NICUs. Babies born before 28 weeks require highly specialised care and have lower survival rates, particularly in resource-limited settings. The long-term outcomes also improve significantly with each additional week of gestation.
Some risk factors can be identified and managed: cervical length measurement at 18–22 weeks can identify women at risk of cervical insufficiency (treatable with a cervical cerclage). Progesterone supplementation reduces recurrence risk in women with prior spontaneous preterm birth. Smoking cessation, treating infections, and avoiding extreme physical stress reduce risk. However, many preterm births have no identifiable preventable cause. Use the [Pregnancy Due Date Calculator](/pregnancy-due-date-calculator/) to accurately track your gestational age.