If you have two children, how long is the interval?

Many people ask this question and also have many answers. But it is not easy to be "scientific".

To be scientific, we should first define what we want to describe strictly, and the complexity of this problem is that it is difficult to define "reasonable" or "good".

Is it from the child's point of view or the mother's point of view?

from the child's point of view, is it to examine the child's IQ or EQ, or psychological development and personal achievement? If you don't make a strict definition, you will just talk about it.

In order to answer this question scientifically, a far-reaching article was published in the New England Journal at the end of last century, which answered this question from the perspective of newborn health.

From the perspective of newborn health, gestational age and weight at birth are two important indicators. These results are closely related to the health of the child after birth and the health of childhood and adolescence. Therefore, this article focuses on these two indicators: the risk of premature delivery and the risk of low birth weight.

This article studies more than 17, newborns delivered in Utah in the past eight years, and finally comes to the conclusion that it is the most ideal situation to get pregnant one and a half to two years after giving birth to the previous one only from the perspective of gestational age and birth weight.

The study found an interesting "J- shaped curve", that is, the risk of premature delivery and low birth weight gradually decreased with the increase of the interval between two fetuses at first, and reached the lowest risk in one and a half to two years, and then increased with the increase of the interval between two fetuses.

J- shaped curve

(source: effect of the interval between pregnancies on perinatal outcomes.)

Specifically, compared with re-pregnancy one and a half to two years after giving birth to the previous fetus, the risk of interval less than half a year is about 1.4 times, and the risk of interval more than 1 years is about 1.5-2 times.

This article is widely cited because of its large sample size and excellent experimental design. The conclusion of this article is still used in the latest edition of Obstetric Evidence-Based Guidelines.

In addition, from the mother's point of view, there are many literatures about the interval of second pregnancy after cesarean section, and the conclusion is relatively consistent, that is, it is suggested that the incidence of pregnancy and childbirth complications is relatively low if it exceeds one and a half years. Similarly, the risk of complications increases when the interval is too long. For example, I have done research on this and found that the risk of complications is significantly increased in scarred uterus with an interval of more than 13 years.

Therefore, based on the above data, regardless of other social, humanistic and psychological factors, it is an ideal interval to conceive a second child one and a half to two years after giving birth to the first child, only from the perspective of perinatal health of mother and child.

Although this "J- shaped curve" shows an ideal time period, this interval is not so dogmatic, and the task of pregnancy must be completed within six months.