1 Department of Gynecology and Obstetrics, 2 Department of Pathology and 3 Department of Gynecology and Obstetrics, Stanford University, Stanford, CA 94305 USA
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Abstract |
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Key words: blastocyst/IVF/multifetal reduction/quadruplet/spontaneous conception
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Introduction |
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Case Report |
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The patient underwent gonadotrophin-releasing hormone down-regulation followed by controlled ovarian hyperstimulation with FSH/human menopausal gonadotrophin. The couple admitted to having intercourse 5 days prior to the retrieval where 24 oocytes were recovered and inseminated, resulting in 18 zygotes. These were cultured in P1 medium containing 10% synthetic serum substitute (SSS, Irvine Scientific) until day 3. Embryos were then transferred to blastocyst medium (Irvine Scientific) + 10% SSS until day 5. Extended culture yielded 8 blastocysts. Two expanded blastocysts with a well-defined inner cell mass and trophectoderm were transferred on day 5, and the remaining 6 blastocysts were frozen.
The patient conceived and an ultrasound scan at 7 weeks gestation showed a quadruplet pregnancy with what appeared to be thick dividing membranes and a lambda sign between all four sacs. Subsequent ultrasound examinations throughout her gestation showed good interval growth of all four fetuses. She delivered three girls and one boy at 32 weeks gestation by elective Caesarean section. Baby A (boy) and baby B (girl) had separate placentas, whereas the placentas of baby C (girl) and baby D (girl) were fused. To further determine the zygosity, cord blood samples of each baby were tested for DNA short tandem repeat polymorphisms at 8 microsatellite loci (Scharf et al., 1995). The loci SE33, HUMTH01, HUMvWA31/A, D21S11, CSF1PO, and D7S796 were genetically informative and showed the boy and one girl to be fraternal, and the other two girls to be identical (Figure 1
). Pathological examination of the placentas revealed no evidence of vascular anastomoses between the placentas of baby C and baby D, and histological section of the dividing membrane was consistent with a diamniotic, dichorionic membrane. These findings, along with evidence from the DNA studies, suggest that babies C and D were derived from a single zygote in which division occurred before implantation. All babies had an uneventful neonatal course and were discharged home within 10 weeks of delivery.
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Discussion: |
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Although it is still debated whether blastocyst transfer improves pregnancy rates, blastocyst culture may help facilitate the selection of the best two embryos to eliminate triplet or greater gestations while maintaining an optimal pregnancy rate (Milki et al., 1999, 2000a
,2000b
). Blastocyst transfer is now routinely used in our programme to help limit the number of embryos transferred in patients at risk. Indeed it was carefully planned for this couple, with the expectation that the gestation would not exceed twins. There is, however, the rare exception where monozygotic splitting can occur with a resultant higher number than twins. We have previously reported a 4% incidence of monozygotic twinning with blastocyst transfer in a multi-centred study (Behr et al., 1999
, 2000
). As expected, these pregnancies are monochorionic, since with blastocyst transfer, embryo splitting occurs on or beyond day 5 after the inner cell mass has developed and cells destined to become chorion have already differentiated (Cunningham, 1997). In this patient with quadruplets, it would appear that the two transferred blastocysts led to fraternal twins, and a spontaneous conception with embryo splitting in vivo by day 4 resulted in identical twins. However, a recent case report showed early ultrasound findings of a trichorionic/triamniotic pregnancy resulting from the transfer of two blastocysts in a woman with bilateral salpingectomies. One of the blastocysts had herniated in vitro through a small hole in the zona pellucida and formed two half blastocysts of similar size, connected by a narrow bridge, with both inner cell mass and trophectoderm components ( Langendonckt et al., 2000
). With this case in mind, it is possible that the monozygotic twins in our patient could have resulted from one blastocyst splitting. Even if that were true, at least one fetus would have been conceived spontaneously, which is incontestable based on the genetic testing.
Concurrent spontaneous conception with IVF is possible as some oocytes can be missed in patients with numerous follicles, despite careful attempts at harvesting all oocytes. Most IVF practitioners have on occasion recovered additional oocytes from the cul de sac when they suction the serosanguinous fluid at the end of the retrieval. Furthermore, sperm survival from intercourse may be prolonged in the presence of copious cervical mucus as seen with high levels of oestrogen in stimulated cycles. Even in non-stimulated cycles, the estimated probability of conception was reported at 0.10 when intercourse occurs 5 days prior to ovulation in a healthy population (Wilcox et al., 1995). Based on the case presented here, it may be prudent to caution IVF patients against unprotected intercourse after the initial days of controlled ovarian hyperstimulation if they have patent Fallopian tubes, normal semen parameters, and particularly if they will not consider multifetal reduction in the event of conception of a high-order multiple pregnancy.
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Notes |
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References: |
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Behr, B., Fisch, J.D., Milki, A.A. et al. (1999) Blastocyst transfer is associated with an increased incidence of monozygotic twinning. Hum. Reprod., 14 (Suppl.), 181
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Submitted on March 16, 2001; accepted on August 2, 2001.