When is it safest for baby to be born

How Many Weeks Is Preterm

References The March of Dimes and “The Global and Regional Toll of Preterm Birth”

In the USA one in eight pregnancies end in preterm or early delivery of the baby (fetus).   Does this matter – and is there anything you can do to prevent this happening to your baby?

The results of a study done at Drexel University College of Medicine Philadelphia, by Dr L Goldenberg and Dr Alan Fleischman and published in “Obstetrics and Gynecology” journal December 2009 edition  – showed some interesting results.

Firstly, what does preterm or premature birth mean?   –  the delivery of the baby before 37 weeks of age (gestation).   Between 1990 and 2006 the rate of premature births in the USA increased by more than 20 %.   Throughout the world the number of premature babies is thought to be about 9.6%  approximately 13 million babies.

What is the likely outcome for premature babies?   The majority of these babies will usually go home after a period of time in a Neonatal Intensive Care Unit.   Unfortunately this is not the case for all of them and many have long term disabilities such as cerebral palsy, difficulties learning, hearing and vision challenges and ongoing lung problems amongst other challenges.   Half of all children who have neurological (brain and nervous system) disabilities are children who have been born prematurely.

The March of Dimes Prematurity Campaign is creating awareness of the effects of prematurity and trying to identify possible causes.

Part of the study done by Dr L Goldenberg and Dr Alan Fleischman was to assess the opinions of first time mothers, aged 21 to 45 and assess the results to the question “What is the earliest point in pregnancy that it is safe to deliver the baby, should there not be other medical complications requiring early delivery?”

The results were that more than 50% said 34 – 36 weeks, 41% said 37 – 38 weeks, and only 8% said 39 – 40 weeks.   (650 expecting mothers took part in the survey).

However, recent studies show that a baby who is born at 37 – 38 weeks – will have a greater chance of ongoing lung problems and learning challenges, than a baby who is born at 39 weeks of after.   The statistics are worse for babies who are born between 34 – 37 weeks.   They have a far greater risk of very serious health problems in their first year of life than a baby who is born at 39 weeks or after.

The increase in the number of babies born prematurely – could be due to increase in fertility drugs, increase in the number of women over 35 having babies, and increased stress levels.

Expecting mothers who are more at risk of premature birth are likely to

  • Previously have had a preterm infant
  • Suffer from an existing medical condition eg high blood pressure or diabetes
  • Be obese or underweight
  • Use alcohol, nicotine, or illegal drugs
  • Not attend prenatal/antenatal care

Dr Goldenberg’s opinion is that TV shows and media reports of very premature infants who survive – leave women with the impression that if babies come only a little early – they should have no problems.   Dr Fleischman emphasizes that the last five weeks of the fetus’ development are crucial – particularly for the brain – which increases by almost 50% in those weeks.

Because of the evidence regarding preterm birth – some experts now classify 34 – 36 weeks as “late preterm”.   37 – 38 weeks is now termed “early term”.

The conclusion is that expecting mothers and their Health Care Professionals need to be better informed about the long term risks to the baby, of delivery before 39 weeks.
The March of Dimes recommends that delivery of the baby should be delayed til after 39 weeks – unless the health of the mother or baby is at risk.   Delivery of the baby at 39 to 40 weeks is safest.

Dr Robert L Goldenberg.Prof Obstetrics and director of Research, Drexel University College of Medicine Philadelphia, and Dr Alan Fleischman MD Medical Director March of Dimes.    Obstetrics and Gynecology Journal December 2009

White Paper:  “The Global and Regional Toll of Preterm Birth” a joint effort of the March of Dimes, and data from the Bulletin of the World Health Organisation (WHO)


I personally think the confusion comes from the fact that women know they will be pregnant for 9 months – so 9 x 4 weeks = 36 weeks.   Plus there is the confusion around being told you are pregnant 2 weeks earlier than you know you could be (because expected date of delivery is worked out from the date of your last monthly period – not when you ovulated and when you most probably had intercourse!! Or a few days either way) … or am I confusing the issue even more now???

Ros Vroom April 2010