# What is the probability of having a second pregnancy with IUGR?

The odds of a pregnancy with an Intrauterine growth restriction (IUGR) appear to be ~5% in the general population, but, after some searching through Pubmed, I have not been able to find if that number is impacted by a previous IUGR. Is the probability changed for subsequent pregnancies?

• Welcome to MedicalSciences.SE. In order to help, I have edited your question to make it more clearer. When using acronyms, please can you define the abbreviation as described in this meta post to help those who may not know what you mean? Aug 15, 2019 at 5:47
• The causes of IUGR are so many that I don't think you'll find an answer as asked. If it was an untreatable maternal cause, the risk is higher than if it is treatable, and if it was a placental problem, the risk of a repeat is lower. I don't tink it would serve anyone to research or even calculate a number while overlooking these facts. Aug 15, 2019 at 15:19
• @ChrisRogers - Since IUGR is defined as babies weighing below the 10th %ile, the incidence should be about 1 in 10. When adjusted for maternal size and other constitutional factors, the true incidence is estimated to be from about 3-7% of births in the US (depending on the author). Aug 15, 2019 at 15:21
• I feel a responsibility for people I refer here. :) "... it is far more likely to be a null result that researchers felt "wasn't worth publishing." I agree that the statistic is of no value. Kinda like asking, "What is the probability of having another surgery if you've already had one?" Umm... if you need the surgery, does it matter? Does it matter what the surgery was for? (If it's for, say, cosmetic enhancement, then the probability is pretty high. Look at Michael Jackson. If it's for appendicitis, it's rather close to the rate of first surgeries for all people.) Aug 16, 2019 at 1:43
• But it was of statistical value when we first started studying it. Studying repeat occurrences narrows in on genetic and physiologic factors, and severity of those factors. But I haven't found anything suggesting what the severity of those factors, or environmental ones, etc., may be. Thus the question. Perhaps further discussion on the merit of the question would best be performed in a chat? (I don't know if I can chat, as I have a low number of points) Aug 16, 2019 at 2:08

Patterson et al (1986) may be a bit outdated, but showed that for first pregnancies 2.5-10th percentile (9.6% of their sample), second pregnancies were 14.2% in that same category plus 3.9% less than 2.5th percentile (overall relative risk 2.2).

For first pregnancies <2.5th percentile (2.8% of their sample), second pregnancies were 18.8% in 2.5-10th plus 8% less than 2.5th percentile (overall relative risk 3.3).

These numbers are for all pregnancies; if you look at the original paper they also break out cases where both pregnancies were considered uncomplicated (about half of the mothers) and found similar ratios. Their sample was Hispanic mothers in Texas 1972-1981 with gestational age >=26 weeks. 9596 total mothers.

Derks & Koenen 2018 is a more recent review but most of the studies mentioned are also a bit older (this isn't my area of expertise at all, so I don't know if any practices have shifted that would change expectations today), and they have varying definitions for low weight. For most of the studies, recurrence was in the 20-30% range, consistent with Patterson if you expect the population risk to be 10%.

I did not dig further to find if any of these studies used a definition that attempted to measure "true" IUGR which, as discussed a bit in the comments above, might differ.

Derks, J., & Koenen, S. (2018). Fetal Growth Restriction: Recurrence Risks. Placental-Fetal Growth Restriction, 263.

Patterson, R. M., Gibbs, C. E., & Wood, R. C. (1986). Birth weight percentile and perinatal outcome: recurrence of intrauterine growth retardation. Obstetrics and gynecology, 68(4), 464-468.

• I know downvotes need not be explained, but here I would definitely appreciate it. Aug 16, 2019 at 23:38
• This is a great answer. Thank you! I was not able to find relevant google scholar results when I was searching, but I used different verbiage. Seems like I need to improve my google fu. I will wait a day to accept the answer, but this one seems very well done. Aug 17, 2019 at 0:37