Impact of the sex of first child on the prognosis in secondary recurrent miscarriage.
BACKGROUND
The carriage of a male fetus often initiates maternal immunological reactions against male-specific minor histocompatibility (HY) antigens, which, in theory, could result in subsequent recurrent miscarriage (RM).


METHODS
Information about subsequent pregnancy outcome was procured among 182 women with RM after a birth (secondary RM) referred since 1986 using questionnaires, telephone interviews and registers.


RESULTS
Significantly more of the women had had a male first-born as compared with a female first-born (110 versus 72; P < 0.02). By January 2002, 58% of those who had a male first-born had given birth to a second live infant compared with 76% of those who previously had had a female first-born (P = 0.01). Women in the former group had a significantly lower chance of having a second child than those in the latter (adjusted hazard ratio 0.59; 95% confidence interval 0.41-0.86). The number of miscarriages after admission and the risk of secondary infertility were significantly greater in women with a male first-born than among those with a female first-born (P < 0.001 and P = 0.02; respectively).


CONCLUSIONS
A male first-born seems to be associated with a less favourable reproductive potential among women with secondary RM. Maternal immunization against HY antigens may be responsible for these findings.
Christiansen
O B
OB
Fertility Clinic 4071, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. obc@pregnancyloss.dk
Pedersen
B
B
Nielsen
H S
HS
Nybo Andersen
A-M
AM
D000026:Abortion, Habitual / Q000453:epidemiology / Q000276:immunology*; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D017584:Reproductive History; D012737:Sex Factors