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Thursday, July 3, 2003
When males lead to miscarriages
By ROWAN HOOPER
At temples all over Japan, there are stone statues wearing aprons and caps of red cloth. Someone once told me that the cloth was supposed to keep the statues warm at night and protect them when it rained. What my friend neglected to say was that many of these statues are dedicated to mizuko, literally "water child," an aborted or miscarried fetus.
The ritual of remembrance and apology made to a miscarried or aborted fetus is performed in a mizuko kuyo, a rite without a precise parallel in the West.
Those wanting to know why Western society is more reticent about its own water children can read "Motherhood Lost," by Linda Layne (published by Routledge, 2003). Layne is an anthropology professor at Rensselaer Polytechnic Institute in Troy, N.Y. She suffered the first of seven miscarriages in 1986.
Layne says that the experience of pregnancy (for middle-class American women, at least) has changed, and that many women now think of their fetuses as "babies" much earlier than had previously been the case. But at the same time, she said, parents who lost babies found themselves without adequate social support, since deep-seated cultural taboos prevented friends and family from talking about the loss.
About 15 to 20 percent of pregnancies in the United States end in miscarriage or stillbirth each year. A smaller proportion of women are unfortunate enough to suffer, like Layne, a further miscarriage.
There are several theories as to why some women undergo recurrent miscarriages. This week in Spain an international conference of fertility experts heard that women who give birth to a boy as their first child are more likely to suffer a subsequent miscarriage than women whose first baby is a girl.
Ole Christiansen, a consultant registrar at the Rigshospitalet Fertility Clinic in Copenhagen was addressing the annual conference of the European Society of Human Reproduction and Embryology, in Madrid. He said that giving birth to a boy first was not only a risk factor for subsequent miscarriages, but for women (like Linda Layne) who suffered unexplained secondary recurrent miscarriages (SRM) it could mean that they would never manage to carry a child to full term again unless doctors gave them appropriate treatment.
"Giving birth to a son is known already to be a prognostically negative factor in many obstetrical complications," said Christiansen.
"Therefore we wanted to assess the impact of the gender of the first child on the outcome of subsequent pregnancies among patients with unexplained secondary recurrent miscarriages."
He studied 204 SRM patients admitted to clinics between 1986 and 2000 and obtained information on subsequent pregnancy outcome in 181 patients admitted before 2000.
Among the patients admitted before 2000, only 54.4 percent of those who gave birth to a boy in their first pregnancy had given birth to a second live baby by January 2002, compared with 73 percent of women whose first child was a girl.
Among a subset of women who did manage to have a second child after a series of miscarriages, those whose first child was a boy had an average of 3.9 miscarriages before achieving a second birth, while women whose first child was a girl had 3.5 miscarriages before delivery of a second child. The difference might seem small, but it is statistically significant. Average birth weights of the second children tended to be 181 grams higher where the first-born was a girl.
Having a boy first seems to take something out of women.
Christiansen said: "Our study shows that the majority (54.4 percent) of those who gave birth to a boy in their first pregnancy go on to have a second child. However this percentage is lower than for those who gave birth to a girl first.
"Among my patients I have at least 50 who never have a second child after the first birth of a boy, whereas approximately 20 patients did not experience another birth after having a girl. So there are patients who will never get a second child in both groups, but the risk is larger among women whose first child was a boy."
He believes that the way women's immune systems react to male fetuses is the explanation. Genes from the father have a big influential on placental growth and function, so it's not surprising that in some women there is a reaction against this.
"These women may have raised an immunological reaction against tissue types that are expressed on the surface of the placenta in pregnancies with boys," he said. "The placenta is created from the fetus, and if it is a boy it will carry these male-specific tissue types. The mother's immune system may be reacting by forming antibodies, but also the mother's white blood cells may be reacting against the placenta."
First pregnancies usually proceed to full term because the fetus becomes safely established before the mother's immune system starts to react to the male tissues. However, the immune system may remain activated after delivery and affect subsequent pregnancies, said Christiansen.
"This is an epidemiological study, so we cannot be sure that such an immunological reaction is the explanation for our findings. However, no genetic disorder following the known rules of inheritance, can explain the findings.
"The impact of the gender of the first-born child on successive pregnancies is suggestive of something that has memory and only two tissues in the body are thought to have memory: the central-nerve system and the immune system."
Christiansen's work may improve the chances of a successful pregnancy for women suffering recurrent miscarriages. It is work that relies on understanding that there is a genetic conflict between male and female interests.
"For many years it has been well-known that pregnancies with boys carry an increased risk for a long series of obstetrical complications compared with girl pregnancies. We believe that our research will be able to clarify whether these complications may be related to immunization against male-specific antigens. If this turns out to be the case, then I believe that we already have a quite efficient treatment."
Rowan Hooper welcomes comments at firstname.lastname@example.org