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We moved into 57 boulevard Barbès in October 1999, because we were planning to have a child.  The apartment, on the treetop level of the boulevard, has two bedrooms, a big living-room and an office, all linked by double-doors and a long southeast facing balcony accessible by six French windows.  As we settled in, we imagined all the different circuits a child could find in such an apartment, how the apartment would be in different seasons, and how work, living, and play could intermingle there.  In November 1999, Anne stopped taking the pill for the first time in twelve years.  We thought it would take several months, but in February 2000 her period was late.  Early on the morning of February 19th, I crossed the Boulevard to the 24-hour chemist on the corner of rue Doudeauville, to buy a pregnancy test.  Anne took it to the bathroom with her and ten minutes later we brought it to the window to examine it.  The test paper inside was pink.

In the afternoon of March 19th, Anne went to see her gynaecologist for a preliminary examination.  When she returned, she told me that her gynaecologist had a small ultrasound machine and had offered to do a brief ‘un-official’ scan (usually, the first scan would not be done before the twelfth week).  The scan clearly showed two walnut-sized forms, side by side, in the upper hemisphere of the womb.  The gynaecologist was careful to point out that, in many such cases, the second fœtus does not survive the first three months of pregnancy, and we should not assume anything before the official scan.  We had to wait until May 5th, at a clinic on Place de la Republique, for official confirmation of a multiple pregnancy.  Each foetus was healthy and roughly equivalent in size and development.  Each had it’s own placenta and amniotic sack (dichorionic and diamniotic).  In such cases, the gynaecologist assumes that the twins are fraternal or dizigote i.e., originating from two eggs fertilised by two spermatozoids.

The pregnancy progressed normally until early July, when Anne began to experience regular and painful contractions.  She was taken into the maternity hospital and put on medication to reduce contractions, and was given cortisone injections to develop the lungs of the babies in case of premature birth.  She was only released under strict orders that she would stay lying down until the term of her pregnancy.  The rest of the summer was a quiet battle to keep the birth at bay until the feotii were sufficiently developed.

It finally happened on the 26th of September 2000, at the maternity hospital on rue Bluets in the 11th Arrondissement, thirty-six weeks after conception.  The twins were well placed in the womb, each with head down and the first twin, Bo, well engaged in the birth canal.  The decision was made to allow a natural birth without a Caesarian or inducing drugs.  The birth was, however, very difficult, especially for Bo.  Anne’s convalescent Summer meant that she was in an exhausted state by the time of the birth, and she had not been able to attend prenatal preparation classes that would have taught her how to push with the contractions.  The labour lasted fifteen hours.  At ten minutes past midnight Bo was pulled out with forceps after a long struggle, that left her scarred and bruised, with a temporarily deformed cranium.  Lotti’s birth forty minutes later was easier.

In the first two years of their lives, despite all the similarities, Bo & Lotti did not look like identical twins.  Bo’s 2.6 kilos at birth looked significantly larger than Lotti’s 2.2, and the ratio remained more or less the same as they grew.  At eighteen months Bo was almost a kilo heavier than her sister.  Bo’s cranium continued to have an ovoid form compared with her sister’s relatively square forehead and flat top.  Moreover, Lotti was born almost bald, while Bo had some hair, which grew longer and thicker than her sister’s, well into the second year.  After her bruises and scars had healed, Bo continued to have delicate skin, always breaking out in rashes, while Lotti’s skin was silky smooth.  Lotti’s face formed easily into a laugh, while Bo, even when she was smiling, would always look slightly worried.

But by their second birthday all these differences had ironed themselves out.  Somewhere along the line, Lotti had caught up in weight-gain and hair-growth, or maybe it was Bo who had slowed down.  The two craniums settled into the relatively square forms they have to this day, and Bo’s skin problems disappeared, as did her worried expression.  In the third year of their life, almost nobody we knew could tell them apart.  Even we occasionally, had to hesitate.

Are Bo & Lotti identical twins?

The immediate assumption was that they were fraternal twins, since there were two amniotic sacks and two placentas.  However, several facts perturb such a thesis: Monozygotic twins originate from one fertilized egg which then splits in two.  They can then develop in one or two amniotic sacks.  They can have a common placenta or two separate placentas.  This all depends on how early the egg splits.  Eggs that split before three days will generally develop in two amniotic sacks with two placentas.

The degree of resemblance between monozygotic twins depends on how early the egg splits.  If the split happens early, there will be greater physical autonomy.  Moreover, cranal form and size at birth is as much dependant on the position in the womb as on genetic information.

The pill stabilizes hormonal activity in a woman’s body.  Dizygotic pregnancies usually result from a hormonal irregularity that prompts the ovaries to produce two or more eggs simultaneously.  A woman who has stopped taking the pill after several years is less likely to produce more than one egg (and therefore to have a dyzigote pregnancy) because her hormonal activity will be very regular.  Anne had been using the pill for twelve years.  A twin pregnancy in such a case is most likely to be monozygote.

Finally, dizygotic twins are often hereditary.  The hormonal irregularities that prompt the production of two eggs simultaneously are handed down from mother to daughter.  However neither of us have twins in our families, close or distant.

We can reasonably assume that Bo and Lotti are identical twins resulting from a single fertilized egg which split sometime during the first three days after conception, allowing the development of two amniotic sacks, two placentas and a certain degree of independence in their physical development before birth.

This thesis can be verified by a genetic test.  But our pediatrician has discouraged us from testing, since it would have no relevance to the health or development of the children, and is expensive, not being covered by public or private health insurance.  From a medical point of view, zygosity is, of course, a frivolous concern.