Can twins be born a month or two apart?

Illustration by Slug Signorino

Cecil replies:

You think this is an impossible feat? On the contrary, it happens … well, maybe not all the time, but often enough that medical science has invented terms for it — delayed interval delivery, or sometimes just delayed twins. What’s remarkable isn’t when the first twin dies and the delayed one survives. If the literature is any indication, that’s what happens more often than not in such cases. Once in a while, however, both infants survive. For decades the world record was held by two healthy children born 56 days apart in the early 1950s. Imagine having to explain that your twins were born in different years.

Delayed interval birthing is not, needless to say, the best way to have twins. You can picture the strain on the mother (“You mean we’re not done?“), and it’s none too healthy for the babies. In one study of 48 delayed-twin deliveries, only 40 of the 96 fetuses survived.

But when the first twin is dangerously premature, delaying the second beats losing them both. Delayed interval delivery occurs more often now than 50 years ago, mainly because twins are being born at a higher rate overall: more women are getting pregnant later in life, which makes it more likely they’ll have twins, and assisted-reproduction technologies like in vitro fertilization have a similar effect. Pregnancies involving multiple fetuses are inherently riskier than the usual kind — infant mortality is seven times higher for twins than for single babies and nineteen times higher for triplets. (God knows even the singleton method is no walk in the park — why couldn’t we just be like tortoises and drop eggs in the sand?) For years doctors assumed that if one twin came out early, there was no choice but to get the other one out right away, due to the risk of intrauterine infection. If contractions subsided after the birth of the first twin, standard procedure was to induce labor and deliver the sib anyway, even though it was likely to die.

That’s no longer the default approach. Increasingly the feeling is that if labor stops after emergence of the first baby, the mother is game, and all other conditions are favorable, the arrival of the second should be postponed, or at least not hurried — the fetus will benefit from increased time in the womb. In one recent review of six intentionally delayed twin deliveries (Hamersley et al, Journal of Reproductive Medicine, February 2002), five of the second twins survived. On average gestation was prolonged 93 days. Longest delay: five months.

In most cases of delayed twins the first child dies, but not in all — which brings us back to those twins who both survived despite being born 56 days apart. The 24-year-old mother, who lived in Sydney, Australia, had a uterus didelphys, or double uterus. As rare as that congenital anomaly is, simultaneous pregnancy in each uterus is rarer still. The first baby was born on December 16, 1952 (after 32 weeks in the womb), when the placental membrane ruptured prematurely. The second baby was born February 10, 1953. The deliveries were both easier on the mother than those of her previous two children. Those labors had taken 36 and 24 hours; the first twin, on the other hand, emerged in an hour and a half, and the second popped out in 15 minutes.

Other cases have been reported since. Some involved a double uterus, but in recent years a number of normally equipped women have given birth to healthy delayed twins too. Though the phenomenon is still rare, medical advances may be making it less so. Kalchbrenner et al (American Journal of Obstetrics and Gynecology, November 1998) report that among the five sets of delayed twins and two sets of delayed triplets they encountered in their practice in a little over three years, four of the seven firstborns survived. In one case, the firstborn’s birth weight was only 610 grams (1.3 pounds), and its sibling arrived 93 days later — facts the report lets pass without comment. (One of Kalchbrenner’s co-authors, Howard Kaufman, tells me his group initially thought 93 days between live births was a record but that they later heard an informal claim of 95 days.) Fifty years ago delivering healthy twins eight weeks apart was something to crow about. Today a 13-week interval is all in a day’s work.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.